1
Q
- The specific volume of steam at atmosphere pressure and 2.12 F is 26.80 ft^3/lb. Find ( (a) its -density and (b) its specific weight.
A
A. 0.03731 lb/ft^3 or 0.598 kg/m^3
B. 0.03731 lbf/ft^3
2
Q
- f the density of mercury is 13,600 kg/m^3, find (a) its density in lb/ft^3 and (b) its specific weight in N/m^3.
A
A. 849.0 lb/ft^3
B. 133,416 N/m^3
3
Q
- A pressure gauge connected to a turbine inlet reads 400 psi. A vacuum gauge connected in the exhaust trunk of the same turbine reads 28.0 in. Hg. The barometer reads 30.1 in. Hg. Find: (a) the absolute pressure the turbine inlet, psia, and (b) the absolute pressure in the turbine exhaust trunk, in. Hg. abs.
A
A. 414.8 psia
B. 2.1 in. Hg. abs
4
Q
- The mercury level in the vertical tube is exactly 760 mm above the mercury level in the reservoir (y = 760.000 mm). the following data also, apply: “water” and “mercury” can be considered to be incompressible fluids having densities of 1000 kg/m^3 and 13,595.1 kg/m^3, respectively. The standard acceleration of gravity is equal to 9.80665 m/sec?. Find:
A. In.Hg.
B. ft.H20
C. Pascals, Pa (N/m^2)
D. lbf/ft^2
E. Psi (lbf/in^2)
A
Ans. 29.92 in Hg
Ans. 33.90ft H20
Ans. 101325.014 Pa
Ans. 2116.8 lbf/ft^2
Ans. 14.7 psi
5
Q
9 . If the difference in height of the water legs in the open manometer is 20 in. (dimension y), find the absolute pressure at point A in psia. The specific weight of water is 62.4 lbf/cu ft.
A
15.42 psia
6
Q
- In the differential manometer points A and B are the at the same height. The mercury used as a manometric fluid stands 9 inches higher in the B leg than in the A leg (y = 9 in.). find the diference in pressure between points A and B in psf. Specific weight of mercury is 849 lbf per cu ft.
A
590 lb/ ft^2
7
Q
- Steam is flowing in a pipe at a velocity of 100 ft/sec. What is the associated kinetic energy per pound of steam flowing?
A
155.28 ft-lb/ lb or 0.20 Btu/ lb
8
Q
- The work delivered by a turbine is 400 Btu per lb of steam supplied when the steam flow is 20,000 lb per hour. Find:
A The specific work in ft. Ibf/ lb
B. The power delivered in hp
C. The power delivered in kW
A
Ans. 311,200 ft-lb/ lb
Ans. 3143 hp
Ans. 2344 kW
9
Q
- A steam turbine receives steam at 1379 kPa gauge and exhausts it to a condenser where the vacuum is indicated as 635 mm of Hg by a gauge. For a barometric pressure of 760 mm of Hg, calculate (a) the absolute pressure at the turbine inlet, kPa, and (b) the absolute pressure corresponding to the vacuum gauge reading kPa, and mm of Hg.
A
A. 1480 kPa
B. 16.7 kPa and 125 mm Hg
10
Q
- A boiler feed pump takes water at an elevation of 10 feet above a chosen datum and pumps it into a boiler drum at elevation 30 feet. Calculate the change in potential energy for the water from pump to boiler in (a) ft. Ibf/ lb, and (b) Btu/lb.
A
A. 20 ft. lbf/ lb
B. 0.0257 Btu/ lb
11
Q
- High pressure steam enters a turbine with a velocity of 125-ft/sec. and leaves the exhaust trunk of the turbine with a velocity of 1000 ft/sec. Calculate the kinetic energy of the steam in ft. Ibf/ lb and Btu at (a) the entrance to the turbine, and (b) the exhaust trunk.
A
A. 242.6 ft.lbf/lb, 0.312 Btu/lb
B. 15,530 ft.lbf/lb, 19.96 Btu/lb
12
Q
- High pressure steam enters a turbine with a velocity of 38.0 meters/sec. and leaves the exhaust trunk with a velocity 305 meter/sec. Calculate the kinetic energy of the steam in kJ/kg and N. m/kg at (a) the entrance to the turbine and (b) the exhaust trunk.
A
A. 0.722 kJ/kg, 722 N.m/kg
B. . 46.5 kJ/kg, 46,500 N.m/kg
13
Q
- Feed water enters a boiler drum at 700 psia, 300 F and a specific volume of 0.0174 ft^3/lb. steam leaves the superheater of the boiler at 600 psia, 550 F and a specific volume of 0.8749 ft^3/lb. Calculate (a) the flow work in Btu/lb associated with the water entering the boiler drum, and (b) the flow work in Btu/lb associated with the steam leaving the superheater.
A
A. 2.25 Btu/ lb
B. 97.2 Btu/ lb
14
Q
- Feed water enters a boiler drum at a pressure of 4826 kPa abs, 148.9 C and a specific volume of 0.00109 m^3/kg. steam leaves the superheater of the boiler at 4137 kPa abs, 287.8 C and a specific volume of 0.0546 m^3 /kg. Calculate (a)the flow work in kJ/kg associated with the water entering the boller drum, and (b) the flow work in kJ/kg associated with the steam leaving the superheater.
A
A. 5.26 kJ/kg
B. 225.9 kJ/kg
15
Q
- A small air compressor delivers 1 lb per min of air while supplying 3 horsepower to the air. Calculate the specific work, ft.lbf/lb, supplied to the air.
A
99,000 ft.lbf/lb
16
Q
- A steam turbine develops 200 horsepower while receiving 400 Btu from each pound of steam passing through the turbine. Calculate the pounds of steam per hour required by the turbine to produce this power.
A
Ans. 1272.5 lb/hr
17
Q
- A steam turbine develops 149 kW while receiving 930 kJ from each kilogram of steam passing through the turbine. Calculate the kilograms of steam per hour required to produce this power.
A
576.8 kg/hr
18
Q
- Many marine steam propulsion plants achieve a fuel rate of 0.45 pound of fuel per shaft horsepower hour. Determine the equivalent fuel rate in kilograms per shaft kilowatt hour.
A
0.27 kg/kW.hr
19
Q
- A certain mountain location where the barometer reads 13.5 psia, the intake manifold gauge on a cross-country truck reads 20 inches of mercury vacuum. Calculate the absolute pressure in the truck intake manifold, psia and in. Hg.
A
3.7 psia or 7.5 in. Hg
20
Q
24, The power delivered by an auxiliary turbine is 500,000 Btu/hr when the steam flow is 4000 lb/hr. Find (a) specific work, ft.lbf/lb, and (b) the power delivered, hp.
A
A. 97,250 ft.lbf/lb
B. 196.5 hp
21
Q
- A working substance enters a thermodynamic steady flow system with the following conditions: p1 = 20 psia, v1= 11.7 ft^3/lb, u1 = 101.6 Btu/lb, V1= 150 ft/sec. The working substance leaves the system with the following conditions: p^2= 25 psia, v^2= 10.3 ft^3/lb, u = 149.0 Btu/lb, and V^2= 500 ft/sec. Changes in elevation through the system are negligible, and 10 Btu/lb transferred heat is added to the fluid as it passes through the system. Determine the work done on or by the fluid, Btu/lb.
A
(-) 46.3 Btu/lb (on)
22
Q
- In a certain non-flow process, the internal energy decreases 20 Btu/lb, and 77,800 ft.lbf/lb of work is done on the substance. Find the heat added or abstracted.
A
120 Btu/lb (abstracted)
23
Q
- Another non-flow process involving 2 kg of working substance there is no heat transferred, but the internal energy increases 5000 joules. Find the work done on or by the substance, J/kg.
A
(-) 2500 J/kg (on)
24
Q
- At pressure of 100 psia and 400 F, the specific volume of steam is 4.934 cu ft/lb, and the specific enthalpy is 1227.5 Btu/lb. Find the internal energy at the given state, Btu/lb.
A
1136.18 Btu/lb
25
29. in a reversible non-flow process with a gas, the initial pressure and specific volume are 270 psia and 4 cu ft/lb, respectively. The final defined by the equation pv^2 = C, where p and v are simultaneous values of pressure and specific volume at any instant during the process and C is a constant. Sketch the process on p- v coordinates. Find the work done on or by the gas during the process, Btu/lb.
133.33 Btu/lb (by)
26
30. The same gas is brought reversibly from the same initial to the same final state as, but the state change is effected by a non-flow constant volume, and a non-flow constant pressure process in combination, Draw the p- v diagram and find the work done on or by the gas if the sequence of process is:
A. Constanf volume followed-by constant pressure is:
B. Constant pressure followed by constant volume
Ans. 74.0 Btu/ lb (by)
Ans. 250 Btu/ lb (by)
27
31. Two pounds of steam initially having a specific entropy of 1.6356 Btu/lb . R and internal energy of 1100.0 Btu/lb undergo a constant temperature reversible non-flow process at 300 F such that the final entropy is 1.5150 Btu/lb. R and the internal energy is 1016.4 Btu/lb. Find:
A. The transferred heat, Btu
B. The work done, ft.lbf
A. (-) 183.31 Btu (abstracted)
B. .(-) 12,526 (on)
28
32. In a marine propulsion plant, the salt water used to condense the exhaust steam enters the condenser at 60 F and leaves a 80 F. the specific heat of salt water is 0.96 Btu/lb. F, the density is 64.0 lb/cu ft, the cooling water rate is 5000 gpm and 1 gal = 231 cu in. Find the heat absorbed by the cooling water, Btu/min.
Ans. 822,000
29
33. During a constant pressure process, the temperature of a certain mass of air is raised from 40 F to 540 F. the specific heat at constant pressure is given by the equation Cp = ^α + βT - ^δT^2 where °= 0.219, β= 0.342 x 10^-4 and ^δ= 0.293 x 10^-8. The average value of Cp, which will be employed in this text for air, is 0.24 Btu/b. F. Find:
A The heat transferred in Btu/lb, using the variable specific heat expression
B. The heat transferred in Btu/lb using the average specific heat
A. 121.4 Btu/lb (added)
B. 120 Btu/lb (added)
30
34. A cylinder contains 0.2 kg of air initially at a temperature of 25 C and a pressure of 140 kPa. After a reversible constant pressure non-flow process, the temperature of the air has risen to 175 C. the initial volume was 0.03m^3 and the final volume is 0.045m^3, the specific heat of air at constant pressure may be taken as 1.0048 kJ/kg.K. Find:
A. the. heat added,kJ
B. the work done, kJ
C. the change in internal energy, kJ
Ans. 30.1 KJ (added)
Ans. 2.10 kJ (by)
Ans. 28.0 kJ (increase)
31
35. During a non-flow process 120 Btu are removed as heat from each pound of working substance While the internal energy decreases 85.5 Btu/lb. Calculate the work involved in the process in ft.lbf/lb and indicate whether work is done on or by the working substance.
(-) 26,840 ft.lbf/lb (on)
32
36. At standard atmospheric pressure, saturated steam has a specific volume of 26.80 ft^3/lb. if the enthalpy of that same vapor is 1150.5 Btu/lb, calculate the internal energy of the steam, Btu/lb.
1077.6 Btu/lb
33
37. One pound of saturated steam at 100 psia is expanded in a reversible non-flow process from a specific volume of 0.017736 ft^3/lb to a specific volume of 4.434 ft /lb. If the pressure remains constant and the internal energy increases 807.5 Btu/lb, and whether it will be added to or abstracted from the working substance.
889.2 Btu/lb (added)
34
38. if problem 2-5 is carried out as indicated, but with the additional provision that the process is also performed at a constant temperature of 327.9 F, calculate the change of entropy for the steam during the process, Btu/lb. R.
1.129 Btu/lb. R (increase)
35
39. One pound of saturated steam at 689.5 kPa is compressed in a reversible non-flow process from a specific volume of 0.2768 m^3/kg to a specific volume of 0.001107 m^3/kg. if the pressure remains constant at 689.5 kPa and the internal energy decreases 1878.2 kJ/kg during the process, determine how much heat will be transferred and whether it will be added to or abstracted from the working substance.
(-) 2068.3 kJ/kg (abstracted)
36
40. Steam at a pressure of 50 psia and a temperature of 281 F has an internal energy of 1095.6 Btu/lb. At these conditions the specific volume of the steam is 8.518 ft^3/lb. determine the enthalpy of the steam in Btu/lb.
1174.4 Btu/Ib
37
41. A reversible non-flow process of a perfect gas proceeds from a pressure of 400 psia to a pressure of 100 psia with a corresponding increase in specific volume of the gas from 0.518 ft^3/lb to 2.072 ft^3/Ib. During the process the internal energy remains constant at 95.76 Btu/lb. Calculate (a) the enthalpy of the gas at 400 psia and 0.518 ft^3/Ib Btu/lb, and (b) change of enthalpy between the initial and final states.
A. 134.1 Btu/lb
B. 0 Btu/lb
38
42. A reversible non-flow process with a gas is defined by the equation pv = C. Show that the work done is given by tne equation.
Wk12 = P1 V1 In (V2/ V1)
39
43. Half a pound of gas undergoes a reversible non-flow process with the pressure remaining constant at 50 psia while the volume increases from 4 ft^3 to 8 ft^3. Find the work done, Btu/lb
74.0 Btu/lb (by)
40
44. Two kilograms of a gas undergo a reversible non-flow process at 350 kPa while the volume increases from 0.4734 m^3 to 0.9468 m^3. Find the work done, kJ/kg.
82.8 kJ/Kg (by)
41
45. During a reversible process with a certain working substance, the entropy remains constant while the temperature increases from 250 F to 450 F. Find the heat transferred.
0 Btu/lb
42
46. One pound of water in changing to steam receives 970.3 Btu at 212 F. Determine the change in specific entropy for the process, Btu/lb.R.
1.444 Btu/lb. R
43
47. Fifty Btu are added to one pound of air during a constant pressure process starting at a temperature of 100 F. Calculate the final temperature of the air, degrees F, for a constant pressure specific heat of 0.24 Btu/lb. F. Then calculate the final temperature of the air, starting at 100 F, for the same quantity of heat added during a constant volume process for which the average specific heat is 0.171 Btu/lb. F.
t2 = 308 F, t2 = 392 F
44
48. A fuel oil heater receives 23,200 lb of oil per hour at 80 F and discharges it at 160 F. The specific heat of the oil is 0.48 Btu/lb. F. Find the heat.
891,000 Btu/hr
45
49. A tank with a total volume of 10 cu ft is filled with air at a pressure of 20 psi gauge and at a temperature of 100 F. Find the specific volume and the total mass of the air in the tank.
A. 5.97 ft^3/lb
B. 1.67 lbs
46
50. A 0.1-kg sample of a gas of fixed composition is compressed in a cylinder. Before compression the gas occupied a volume of 0.05 m^3 and was at a temperature of 30 C and 102.9 kPa. After compression the gas occupied a volume of 0.008 m^3 and was at a pressure of 800 kPa. Find:
A. The temperature of the gas after compression, C
B. The specific volume of the gas before compression, m^3/kg
C. The value of the gas constant, R, for this gas, J/kg.K
A. 104 C
B. 0.50m^3/kg
C. 169.8 J/kg-K
47
51. Air at an initial pressure if 15 psia and temperature of 60 F undergoes a palytropic process such that the final temperature and pressure become 240 F and 90 psia. Find:
A. The polytropic exponent for the process
B. The specific volume when the pressure reaches 30 psia during the process
C. The temperature for the conditions of part (b)
A. 1.2
B. 7.20 ft^3/ lb
C. 584 R
48
52. Air is compressed reversibly in a cylinder from an initial pressure of 15 psia to a final pressure of 60 psia. The initial temperature is 60 F and the initial volume is 1 cu ft. Find:
A. The mass of the air contained in the cylinder, lb
B. The work required if the process is isentropic, ft.lbf
C. The work required if the process is isothermal, ft.lbf
A. 0.078 lbs
B. (-)2630 ft-lbf (on)
C. (-)2997 ft-lbf (on)
49
53. Helium, for which R = 386 ft.lbf/lb. R and k = 1.66, is heated from an initial temperature of 80 F to a final temperature of 180 F in an unknown process. Find:
A. The value of cv
B.. The value of cp
C The change of internal energy, Btu/lb
D. The change of enthalpy, Btu/lb
A. 0.752 Btu/lb-R
B. 1.25 Btu/Ib-R
C. 75.2 Btu/lb
D. 125 Btu/lb
50
54. A quantity of air undergoes a reversible non-flow constant pressure process from an initial temperature of 400 F to a final temperature of 50 F. Find:
A. The work done, Btu/lb
B. The change of internal energy, Btu/Ib
C. The heat transferred, Btu/lb
D. The change of specific entropy, Btu/lb. R
A. (-)24 Btu/lb (on)
B. (-)59.85 (decrease)
C. (-)83.8 Btu/lb ( abstracted)
D. (-)0.1255 Btu/lb. R
51
55. During an isentropic non-flow process with air, the pressure drops from 60 psia to 20 psia. The air has a mass of 0.1 Ib and the initial temperature was 280 F. Find:
A The final temperature,F
B. The heat transferred, Btu
C . The change of internal energy, Btu
D. The workdone, Btu
Ans. 81
Ans.0
Ans. -3.4 Btu
Ans. 3.41 Btu (by)
52
56. During the constant volume non-flow reversible process which occurs in the Otto cycle, 4.0 Btu of heat are added. The cylinder contains 0.01 lb of air, and the initial temperature and pressure are 650 F and 210 psia, respectively. Sketch the process on, p- v and T-s coordinates and find:
A. The final temperature, F
B, The final pressure, psia
C. The work done, Btu
D. The change of internal energy, Btu/lb
Ans. 2990
Ans. 653
Ans. 0
Ans. 400
53
57. Air is compressed in a cylinder during a non-flow reversible polytropic process from an initial temperature and pressure of 80 F and 15 psia to a final temperature and pressure of 235 F and 75 psia. The cylinder contains 0.01 Ib of air, and the area of the piston is 0.2 sq ft. Sketch the process on p- v and T-s coordinates and find:
A. The value of the polytropic exponent,n
B. The work done, ft.lbf
C. The change of internal energy, Btu
D. The heat transferred, Btu
E. The distance the piston moves during the process, inches
Ans. 1.25
Ans. (-)437.06 (on)
Ans. 0.351
Ans. (-)0.211 (abstracted)
Ans. 5.78 in
54
58. Air is heated in a non-flow process fromn 540 R to 1500 R at a constant pressure of 90 psia. The air then expands isentropically until the pressure is 15 psia. Assuming constant specific heats, determine:
A. the heat input, Btu/lb
B. the work output, Btu/lb
C. the change in entropy, Btu/lb. R
D. the heat input, Btu/lb
E. the work output, Btu/lb
F. the change in entropy, Btu/Ib. R
Ans. 230.4 Btu/lb
Ans. 169.1 Btu/lb
Ans. 0.2452 Btu/lb. R
Ans. 240.1 Btu/lb
Ans. 173 Btu/lb
Ans. 0.25327 Btu/lb. R
55
59. During a gas process, the temperature remains constant while the pressure is doubled. How will the specific volume be affected?
Halved
56
60. A dosed tank contains 100 lb of air at a pressure of 200 psia and a temperature of 180 F. The air is subsequently cooled to 80 F. Find
A. the initial specific volume ft^3/Ib
B. the volume of tank,ft^3
C. the final specific volume, ft^3/Ib
D. the final pressure,psia
Ans. 1.184
Ans. 118.4
Ans. 1.184
Ans. 168.8
57
61. Air initially at 75 psia and 65 F is compressed to a final pressure of 300 psia and temperature of 320 F. Find the polytropic exponent for the process.
n=1.4
58
62. Air initially at 25 C and 150 kPa is heated in a constant valume non-flow process until the pressure reaches 750 kPa. Find the required heat transfer, KJ/kg.
Ans. 853.4 KJ/kg (added)
59
63. Air initially at 50 psia and 140 F undergoes a polytropic process such that the temperature becomes 40 F. The polytropic exponent for the process is equal to 1.3. Find the final pressure and specific volume.
Ans. 22.7 psia, 8.15 ft^3/lb
60
64. Air initially at 400 K expands in a constant pressure non-flow process until the initial volume is doubled. Find
A. the heat transfer, KJ/kg
B. the work,KJ/kg
C the change of entropy, KJ/kg.K
Ans. 401.9 KJ/kg (added)
Ans. 114.8 KJ/kg (by)
Ans. 0.6965 K/kg.K
61
65. Air initially at 15 psia and 60 F is brought to a final temperature of 200 F by a reversible non-flow process. Identify the process in each case and find the work required in Btu/lb if
A.n=0
B. n=infinity
C. n=k
D. n=1.2
Ans. constant pressure, 9.6 Btu/lb
Ans. constant volume, 0 Btu/lb
Ans. isentropic, (-)24 Btu/lb (on)
Ans. polytropic, (-)48 Btu/lb (on)
62
66. Air initially at 15 psia and 60 F is brought to a final temperature of 200 F by a reversible non-flow process. Find the heat transferred in Btu/lb if
A.n=0
B. n=infinity
C.n=k
D.n=1.2
Ans. 33.6 Btu/lb (added)
Ans. 24 Btu/lb (added)
Ans.0 Btu/lb
Ans. (-)24 Btu/lb (abstracted)
63
67. Air initially at 100 F and 100 psia and occupying a volume of 0.5 ft^3 undergoes a reversible non-flow constant temperature process such that the final pressure becomes 20 psia. Find the work done, ft.lbf.
Ans. 11,590 ft.lbf (by)
64
68. The value of the Mechanical Equivalent of Heat, J, from the international Tables is 778.169 ft.lbf/Btu. The value of the Gas Constant, R for air as used in the Gas Tables (Keenan, & Kaye) is 53.342 ft.lbf/Ib. R. And from the same
source, we find that at 90 F the value of the isentropic exponent, k, for air is 1.400. Using these data, find the value of cv and cp for air at 90 F, to four significant figures.
Ans. cv= 0.1714 Btu/lb. R and cp= 0.2399 Btu/lb. R
65
69. During an unidentified process with air, the temperature decreases from 600 F to 200 F. Find
A. the change of internal energy
B. the change of enthalpy
Ans. (-)68.4 Btu/lb (decrease)
Ans. (-)96.0 Btu/lb (decrease)
66
70. Four pounds of certain gas receive 50 Btu of heat during a constant temperture reversible non-flow process at 165 F. Find
A. the change of specific entropy, Btu/lb. R
B. the work done, Btu
Ans. 0.02 Btu/lb. R (inacrease)
Ans. 50 Btu (by)
67
71. Air initially at 3000 F and 600 psia expands isentropically under non-flow conditions. Th final volume is six times the initial volume. Find
A. the final pressure, psia
B. the final temperaure,F
C. the heat transferred, Btu/lb
D. the work done, Btu/lb
E. the change of entropy, Btu/lb. R
Ans. 48.8
Ans. 1230 F
Ans. O Btu/lb
Ans. 302.7 Btu/lb
Ans. 0 Btu/Ib. R
68
72. Air undergoes a cycle consisting of a series of non-flow processes listed below:
1-2 constant volume heat addition
2-3 constant presure heat addition
3-4 constant volume heat rejection
4-1 constant pressure heat rejection
The maximum and minimum values for pressure and specific volume for the cycle are 30 psia, 15 psia, 25 ft^3/lb and 12.5 ft/lb. Find
A. heat added, Btu/lb
B. heat rejected, Btu/lb
Ans. 329.8 Btu/lb
Ans. (-)294.9 Btu/lb (rejected)
69
73. During a constant pressure reversible non-flow process with air, the temperature increases from 400 F to 1600 F.
Find the heat transferred in Btu/lb using
A. constant specific heat
B. the air table
Ans. 288.0 Btu/lb (added)
Ans. 314.9 Btu/lb (added)
70
74. During a constant volume reversible non-flow process with air, the temperature drops from 1400 K to 320 K. Find the heat transferred in KJ/kg using
A. constant specific heat
B. the air table
Ans. (-)773.17 KJ/kg (rejected)
Ans. (-)885.17 KJ/kg (rejected)
71
75. Air initially at 3000 F and 600 psia expands isentropically under non-flow conditions. The final volume is six times the initial volume, Using air table, find
A. the final pressure, psia
B. the final temperature, F
C. the heat transferred, Btu/lb
D. the work done, Btu/lb
E. the change of entropy, Btu/lb. R
Ans. 56.8
Ans. 1504 F
Ans. 0 Btu/lb
Ans. 328.5 Btu/lb (by)
Ans. 0 Btu/lb. R
72
76. Air initially at 300 K and 130 kPa undergoes an isentropic non-flow expansion process in which the pressure is reduced to one-fourth the original value. Using Air Tables find
A. the final temperature, K
B.. the final pressure, Kpa
C the change in internal energy, KJ/kg
D. the change in enthalpy, KJ/kg
E. the change in entropy
Ans. 201.6
Ans. 32.5
Ans. -70.4
Ans. -98.6
Ans. 0
73
77. Air initially at 14.7 psia and 80 F is heated in a constant volume non-flow process until the temperature reaches 1500 F. The air is then expanded isentropically until the original volume is tripled. Using Air Tables find
A the heat added at constant volume, Btu/lb
B. the work done, Btu/lb
Ans. 267.24 Btu/lb (added)
Ans. 123.28 Btu/lb (by)
74
78. The liquid at 212 F and 14.696 psia is:
Saturated water
75
79. The vapor at 212 F and 14.696 psia , in the absence of any liquid whatsoever, is:
Ans. Saturated steam or dry vapor
76
80. In the first stage of a gas turbine, air enters a group of nozzles at 1200 F and leaves at 950 F. The entering velocity is negligible. Find
A. the kinetic energy, Btu/lb
B. the velodity, ft/sec, of the air leaving the nozzle
Ans. 60 Btu/lb
Ans. 1734 ft/sec
77
81. A marine propulsion turbine receives steam at the throttle at 875 psia and 940 F at the rate of 100,000 Ib/hr. After an ireversible expansion process, the steam exhausts from the turbine at a pressure of 0.6 psia with a moisture content of 10 percent. At 875 psia and 940 F, h = 1475.6 Btu/lb, At 0.6 psia, hg= 1098.6, hfg = 1045.4. Assume the diference between the entrance and exit kinetic energies is negligible and find:
A. the work done, Btu/lb
B. the power developed, hp
Ans. 481.5 Btu/lb
Ans. 18,920 hp
78
82. A boiler receives feed water at 1200 psia and 250 F (h = 221.0 Btu/lb) and delivers steam from the superheater at 900 psia and 950 F (1480.5 Btu/lb). Find the heat added in Btu/lb.
Ans. 1259.5 Btu/lb (added)
79
83. A boiler receives feed water at 1200 psia and 250 F (h = 221.0 Btu/lb) and delivers steam from the superheater at 900 psia and 950 F (1480.5 Btu/lb). The feedwater entering has a velocity of 3 m/sec and steam leaving the superheater has a velocity of 50 m/sec. Find
A. the additional heat required to accomodate the change in kinetic energy across the boiler, J/kg
B. the percentage error introduced by neglecting the kinetic energy change
Ans. 1245.5 N.m/kg (added)
Ans. 0.043%
80
84. Saturated water at 250 F (v = 0.017001 ft/lb, h = 218.59 Btu/lb, P = 29.8 psia) enters a centrifugal main feed pump and is discharge at 1200 psia. The pump efficiency is 60 percent and the delivery rate is 125,000 lb/hr. Find:
A. the total head developed by pump,ft
B. the water horsepower,WHP
C. the brake horsepower, BHP
Ans. 2864.8 ft
Ans. 180.9 hp
Ans. 301.5 hp
81
85. A water cooled reciprocating air compressor takes in air at 15 psia and 60 F and discharges it at 60 psia and 200 F.Heat is removed in the amount of 21.4 Btu/lb. Assume steady flow conditions and find the work done, Btu/lb.
Ans. (-)55.0 Btu/lb (on)
82
86. In a lube oil cooler, oil enters at 140 F and leaves at 100 F, at the rate of 400 Ib/min. The cooling medium is sea water, which enters at 60 F. The average specific heat of the oil is 0.50 Btu/lb.f and of the salt water is 0.94 Btu/lb.f the flow of the sea water is at the rate of 500 lb/min, find the overboard discharge temperature.
Ans. 77.0 F
83
87. Steam enters the condenser of a marine propulsion plant at 0.5 psia and a quality of 89% at the rate of 100,000 lb/hr and with a velocity of 1000 ft/sec. it leaves the condenser hotwell at saturated liquid without any change in pressure but at a velocity of 10 ft/sec. The salt water inlet (injection) temperature is 70 F and the discharge (overboard) temperature is 85 F. Sea water has a specific heat of 0.94 Btu/lb.F and a density of 64 lb/ft^3 The injection and overboard velocities are substantially equal. Calculate:
A. the rate at which energy is extracted from the condensing steam as heat, Btu/min.
B. the flow of sea water required, gallons per minute (gpm)
Ans. (-)1,588,700 Btu/min (abstracted)
Ans. 13,170 gpm
84
88. Steam leaves a boiler at 600 psia and 750 F at the rate of 75,000 lb/hr through the main steam line, which has a cross sectional area of 0.322 ft^2. Find the velocity of the steam in the line, ft/sec.
Ans. 73.3 ft/sec
85
89. Steam leaves a boiler at 6550 kpa abs and 510 C at the rate of 45,400 kg/hr through the main steam line, which has a cross-sectional area of 0.030 m^2, Determine the velocity of the steam in the line, m/sec. The specific volume of the steam is 0.0525 m^3/kg.
Ans. 22.1 m/sec
86
90. An air compressor takes in 50 ft /min of air at 14.7 psia and 60 F. The air is discharge at 100 psia and 260 F. Find
A. the mass rate of flow of air, Ib/min
B. the volume flow rate at discharge, ft^3/min
Ans. 3.82 lb/min
Ans. 10.18 ft^3/min
87
91. Steam enters the first stage nozzles of a large turbine with negligible velocity at a pressure of 540 psia and a temperature of 800 F. The pressure at the nozzle exit is 220 psia. If the process is isentropic, find
A. the final enthalpy, Btu/lb
B. the kinetic energy at exit, Btu/lb
C. the velocity at exit in ft/sec
Ans. 1302.2 Btu/lb
Ans. 108.1 Btu/lb
Ans. 2327 ft/sec
88
92. An auxillary turbine receives saturated steam at 300 psia with negligible kinetic energy at the rate of 3000 lb/hr. At exhaust the steam pressure is 1.5 psia, and the moisture content is 10 percent. The inside diameter of the exhaust trunk is 12 inches. Find
A. the velocity of the steam in the exhaust trunk
B. the enthalpy of steam in the exhaust trunk
C. the work done in Btu/lb
D. the horsepower developed in the turbine
Ans. 217.4 ft/sec
Ans. 1008.9 Btu/lb
Ans. 194.1 Btu/lb
Ans. 229 hp
89
93. A boiler receives feed water at 1000 psia and 350 F and delivers superheated steam at 900 psia and 840 F. Neglect any kinetic energy changes and find the heat added, Btu/lb.
Ans. 1093.8 Btu/lb
90
94. Saturated steam is supplied to a fuel oil heater at 150 psia and becomes saturated water at the same pressure. Find the heat transferred from the steam, Btu/lb.
Ans. (-)864.2 Btu/lb
91
95. A main feed pump receives water from a booster pump at 230 F and 55 psia and delivers the water at 1000 psia. Assume the process to be isentropic and find the work done in Btu/lb,
Ans. (-)3.48 Btu/lb
92
96. A condensate pump takes suction from the hotwell of a condenser at an absolute pressure of 6 kPa and discharges the water at 340 kPa absolute. The condensate is at 36 C with a density of 994 kg/m^3. The net change in kinetic energy across the pump is negligible. Calculate the power required to drive the pump, kW, when delivering 1.4 m^3/min of condensate if the pump efficiency is 65 percent.
Ans. 12.0 kW
93
97. The total head (TH) for a condensate pump handling water at 100 F is 100 ft. Neglecting elevation and velocity changes across the pump, calculate
A. the pressure difference across the pump in psi.
B. the brake power required to drive the pump when pumping one cubic foot per second of condensate.
Ans. 43 lbf/in^2
Ans. 18.8 hp
94
98. Under steady operating conditions a deaerating feed tank maintains its liquid level 18 feet above the centerline of the booster pump, which is pumping 225 gallons per minute of 250 F feed water froin the tank through a 6 inches inside diameter pipe. DFT operating pressure is 15 psig, and the friction head loss from DFT operating pressure is 15 psig, and the friction head loss from DFT to pump suction is 2.0 feed of water. Calculate the purnp suction pressure in psig.
Ans. 21.5 psig
95
99. A large water-cooled air compressor takes in air at 15 psia and 50 F and delivers it at 90 psia and 270 F. The compressor delivers 35.6 hp to the air, and heat is rejected by the air at the rate 452 Btu/min. Find
A. the change of specific enthalpy, Btu/lb
B. the rate of change of enthalpy, Btu/min
C. the mass rate of flow, lb/min
D. the volumetric capacity of the compressor based on the inlet air, ft^3/min
Ans. 52.8
Ans. 1058
Ans. 20
Ans. 251.7
96
100. A throttling calorimeter is connected to a steam line, and the pressure and temperature in the line are determined to be 205 psi gauge and 390 F from the connected instruments. The calorimeter temperature is 240 F. Barometer is standard. Estimate the enthalpy and quality of the steam line.
Ans. 1164 Btu/lb, 95.6%
97
101. A deaerating feed tank (DFT) receives 200,000 lb/hr of main and auxiliary condensate at an enthalpy of 110 Btu/lb, 8000 lb/hr of auxiliary exhaust steam at 1200 Btu/lb, 2,000 lb/hr of low pressure drains (liquid) at 150 F and an undetermined amount of augmenting steam at 1290 Btu/lb. The DFT operates at 13.0 psig and has negligible steam vent flow, Detemmine the quantity of augmenting steam required, if any, to balance the system, Ib/hr.
Ans. 12,180 lb/hr
98
102. Saturated steam is supplied to a fuel oil heater at 150 psia and becomes saturated water at the same pressure. It requires to heat 2500 lb/hr of heavy fuel oil from 70 F to 210 F. f the specific heat of the fuel oil is 0.51 Btu/lb. F,
how much steam will be used, Ib/hr?
Ans. 206.5 lb/hr
99
103. Water vapor at 2 psia with a moisture content of 0.15 enters the distilling condenser of a marine evaporator plant at the rate of 1500 lb/hr and leaves at the same pressure as saturated liquid. The coolant is sea water with a specific heat of 0.94 Btu/lb. F. Operation requires that the temnperature of the sea water leaving be limited to a maximum of 100 F. To meet this limit, how much sea water must be pumped through the condenser, Ib/min, when the injection temperature is
A.60 F
B. 70 F
Ans. 578 Ib/min
Ans. 770 lb/min
100
104. A deaerating feed tank operates at 15 psig with 32.0 psia saturated steam in the auxiliary exhaust line and saturated vapor at DFT pressure at the vent. Total condensate flow entering is 100,000 lb/hr at 110 Btu/lb, and total low pressure drain flow (liquid) is 3000 lb/hr at 180 Btu/lb. There is no evaporator drain flow. Vapor loss through the vent is negligible. Calculate the required flow of auxiliary exhaust steam, lb/hr.
Ans.11,600 lb/hr
101
105 A marine main propulsion plant delivers 30,000 shaft horsepower at full power. Under these conditions, the deaerating feed tank operates with a shell pressure of 33 psia. The pressure in the auxiliary exhaust steam line is 36
psia. The flow rates and observed temperatures are as shown in the table below. Verify the enthalpy column, and for balanced conditions find
Item Flow rate (lb/ hr) Temp. ( F) Enthalpy (Btu/lb)
Condensate 210,000 106 74.0
Vent 200 1166.2
Drains 18,000 210 178.1
Exhaust steam ? 370 1222.4
Feedwater ? 224.5
A. the required flow rate of auxiliary exhaust steam
B. the feed water available, both in lb/hr
Ans. 32,200 lb/hr
Ans. 260,000 lb/hr
102
106. One pound of air (considered here a perfect gas) with an initial temperature of 200 F is allowed to expand without flow between pressures of 90 and 15 psia. Which of the three processes, pv = c, pv^k = c or pv^1.5= c will produce the maximum work with minimum heat supplied.
Ans. Isentropic process, pv^k=c
103
107. One kilogram of a perfect gas (air) is used as a working, substance in a Carnot power cycle. At the beginning of isentropic compression, the temperature is 326 K and the alsolute pressure is 359 kpa. The absolute pressure at the end of the isentropic compression is 1373 kPa. For this cycle, the isothermal expansion ratio (v3/v2) is 2.0.Calculate
A. the pressures, temperatures and specific volumes at each process termination point.
B. the heat supplied, KJ/kg
C. the heat rejected, KJ/kg
D. the net work
E. the thermal efficiency, %
Ans. v1= 0.2606 m^3/kg, T2 = 478.3 K, v2= 0.100 m^3/kg, p3= 686.5 Kpa abs, T3= 478.3 K, v3= 0.200 m^3/kg, T4=T1= 326 K, v4 = 0.5212 m^3/kg
Ans. 95.17 KJ/kg
Ans. 64.85 KJ/kg
Ans. 30.32 K/kg
Ans. 31.86 %
104
108. Calculate the available energy in Btu/lb for a Carnot cycle with a source temperature of 3460 R, a sink temperature of 520 R and an energy supply as heat of 100 Btu to one pound of a working substance. Then calculate the reduction in available energy, Btu/lb, for a similar Carnot cycle in which all conditions remain the same as before except that the working substance is limited to a maximum temperature of 1960 R.
Ans. 11.5 Btu/lb
105
109. In a ideal steam cycle, heat is added at a constant pressure of 2000 psia. Water entering the boiler has an entropy of 0.0555 Btu/lb. R, and steam leaving the superheater has an entropy of 1.7395 Btu/lb. R. Superheated steam temperature is 1500 F, and heat added is 1744.5 Btu/lb. Heat rejection is carried out in a condenser at a constant temperature of 60 F. Average temperature of the combustion gases in the boiler furnace is 3000 F. Calculate
A. the available energy of the combustion gases with respect to the sink temperature of 520 R, Btu/lb
B. the available energy of an ideal cycle receiving its energy at a constant source temperature equal to the superheated steam temperature, Btu/lb
C the available energy of the ideal steam cycle, Btu/lb
D. the mean effective temperature of the working substance during heat receipt in the original steam cycle, degrees F
Ans. 4951
Ans. 2425
Ans. 868.8 Btu/lb
Ans. 575.9 F
106
110. In a perfectly insulated cylinder and piston arrangement, 1 pound of saturated steam at 212 F is to be mixed with 9 pounds of water at 60 F. The entire heat exchange process is to take place at standard atmospheric pressure. Calculate
A. the final temperature, F
B. the change of entropy of steam, Btu/ R
C the change of entropy of the water, Btu/ R
D. the net change of entropy of the system, Btu/ R
Ans. 172.4
Ans. -1.5056
Ans. 1.7602
Ans. 0.2546
107
111. A Carnot power cycle employing 1 lb of air as a working, substance is presumed to operate between temperature limits of 600 F and 70 F. The pressures at the beginning and end of the isothermal expansion process are 510 psia and 170 psia, respectively. Determine:
A. the change of volume between the end of isentropic expansion and the end of isentropic compression, ft^3/lb.
B. the heat supplied to the cycle, Btu/lb
C. the heat rejected by the cycle, Btu/lb
D. the net work of the cycle, Btu/Ib
E. the cycle thermal efficiency, %
Ans. 12.3
Ans. 79.8
Ans. 39.9
Ans. 39.9
Ans. 50.0%
108
112. One kilogram of a perfect gas (air) is used as a working substance in a Carnot power cycle. At the beginning of isentropic compression the temperature is 325.6 K and the pressure is 359.2 kPa abs. The.pressure at the end of isentropic compression is 1379.0 kPa abs. For this cycle, the isothermal expansion ratio, (v3/v2), is 2. For the cycle, calculate
A the pressures, temperatures and specific volumes at each process termination point (SI units)
B. the supplied, KJ/kg
C. the heat rejected, KJ/kg
D. the thermal efficiency, %
Ans. v1= 0.260 m^3/kg, p1 = 359.2 Kpaa, T1= 325.6 K, v2 = 0.0995 m^3/kg, p2 = 1379.0 kPa, T2 = 478.2 K, v3 = 0.1990 m^3/kg, p3= 689.5 kPa abs, T3 = 478.2 K, v4 = 0.520 m^3/kg, p4 = 179.6 kPa, T4= 325.6 K
Ans. 95.1.KJ/kg
Ans. 64.8 KJ/kg
Ans: 31.9 %
109
113. An engine working in a closed thermodynamic cycle produces 400 Btu of work/lb of working substance passing through the machine. The pump in the cycle requires 6 Btu/lb of working substance in performance of its duty. Calculate the net work of the cycle, Btu/lb.
Ans. 394
110
114. A reversed Carnot cycle using 1 lb of air is assumed to constitute a refrigerating cycle between the temperatures of 140 F and 40 F. The isothermal expansion ratio for the cycle is 3. The pressure at the beginning of isothermal
expansion is 50 psia. Calculate
A the heat added-to the working substance, Btu/lb
B. the heat rejected by the working substance, Btu/lb
C. the net mechanical work required by the cydle, Btu/lb
Ans. 37.63
Ans. 45.16
Ans. 7.53
111
115. A certain working substance receives 100 Btu reversible as heat at a temperature of 1000 R from an energy source at 3600 R. Referred to as a receiver temperature of 80 F, calculate
A. the available energy af the working substance in Btu
B. the available portion of the 100 Btu added at the source temperature, Btu
C. the reduction in available energy between the source temperature and the 1000 F temperature, in Btu
Ans. 63
Ans. 85
Ans. 22
112
116. A working substance receives 100 Btu of energy reversibly at a constant temperature of 1000 F in a situation. which employs a receiver having a constant temperature of 120 F. Calculate
A. the available energy of the working substance, Btu
B. the gain in available energy that could be realized with a receiver maintained at an 80 F temperature.
Ans. 60.3
Ans. 2.7 Btu
113
117. Combustion gases at 3000 F supply 100.0 Btu of energy reversibly as heat to water and its vapor at 190 psia. Water enters the heater at 190 psia and 60 F and leaves as steam at 190 psia and 500 F. A receiver maintained at 60 F is available to condense the steam to a saturated liquid during removal of the unavailable energy. Calculate
A. the available energy of the heat added at combustion gas temperature with respect to the 60 F receiver, Btu
B. the available portion of the 100.0 Btu if it were all supplied at the 500 F temperature of the steam leaving the heater, Btu
C. the available portion of the 100 Btu when added at the constant pressure of 190 psia, Btu
Ans. 85.0
Ans. 45.8
Ans. 34.0
114
118. One pound of a certain working substance receives 100 Btu of heat at a constant temperature of 2000 R. Calculate
A. the change of entropy for the substance, Btu/lb. R
B. the available energy in Btu/lb with respect to a 100 F receiver.
C. the change of entropy for 100 Btu added to 1 lb of the same substance at 1000 R
D. the available energy in Btu/lb at this latter temperature , the receiver temperature remaining 100 F
Ans. +0.05
Ans. 72
Ans. +0.10
Ans. 44
115
119. One pound of steam per second at 1,000 psia and 600 F expands adiabatically in a turbine to a pressure of 1 inch of mercury absolute where its enthalpy is 800.0 Btu/lb. Calculate
A. the change of entropy of steam during the process, Btu/lb. R
B. the engine efficiency of the turbine in %
C. the additional heat rejected because of the irreversibility of the process, Btu/lb
D. internal horsepower developed
Ans. +0.044
Ans. 95.0%
Ans. 23.7
Ans. 635
116
120. One pound of air at 100 F is mixed with another pound of air at 40 F. The mixing process is constant pressure with constant specific heat. Calculate
A the final mixture temperature .
B. the change of entropy for the lb of gas originally at 100 F, Btu/lb.R.
C. the change of entropy for the lb of gas originally at 40 F, Btu/Ib.R.
D. the change of entropy for the.final mixture, Btu/Ib.R.
Ans. 70 F
Ans. -0.01321
Ans. +0.01398
Ans. +0.00077
117
121. One kilogram of air at 38 C is mixed with another kilogram of air at 4.0 C. The mixing process is carried out at constant pressure with constant specitic heat. Calculate
A. the final mixture temperature, C
B. the change of entropy of air originally at 38 C, KJ/kg. K
C. the change of entropy of air originally at 4.0 C, KJ/kg.K
D. the net change of entropy for the final mixture, KJ/kg.K
Ans. 21.0 C
Ans. -0.0565
Ans. +0.0598
Ans. +0.0033
118
122. A steam turbine receives steam at 600 psia and 600 F and exhausts it at 1 inch of mercury absolute to a condenser. The turbine develops 400 Btu of work from each pound of steam passing through. Calculate
A. the ideal work of the turbine, Btu/lb
B. the engine efficiency of the turbine, %
Ans. 466.2 Btu/lb
Ans. 85.8 %
119
123. A heat source is supplying 1000 Btu to each pound of a working substance in a closed thermodynamic power cycle. The sink is receiving 650 Btu/lb of working substance. The system pump requires 6.0 Btu/lb of substance pumped.
A What is the net work of the cycle?
B. What is the thermal efficiency of the cycle, %?
Ans.-350 Btu/lb
Ans. 35.0 %
120
124. A closed thermodynamic cycle has a thermal efficiency of 30 percent. Heat supplied from an energy source is 800 Btu/lb of working substance. Calculate
A the net work of the cycle, Btu/lb
B. the heat rejected, both in Btu/lb
Ans. 240
Ans. 560
121
125. A Carnot power cycle has a maximum cycle temperature of 800 F. The change of entropy for the heat addition process is 0.085 Btu/lb.R. Heat is rejected at the rate of 45.0 Btu/lb. Determine
A. the heat supplied, Btu/lb
B. the net cycle work, Btu/Ib
C. the minimum cycle temperature, F
Ans. 107.1
Ans. 62.1
Ans. 69.4
122
126. A Carnot power cycle operating between the temperature limits of 65 F and 550 F uses air as the working substance. The pressure at the end of the constant temperature heat rejection process is 15.0 psia. The pressure at the beginning of the isentropic expansion process Is 34.3 psia. Calculate
A. the cycle thermal efficieny.
B. the pressure at the end of the isentropic compression process
C. the change of entropy for the heat addition process Btu/lb.R .
D. the heat supplied, Btu/lb
E. the net cycle work, Btu/lb
Ans. 48.0%
Ans. 148.1 psia
Ans. 0.1002 Btu/lb.R
Ans.101.2 Btu/lb
Ans. 48.6 Btu/lb
123
127. In Carnot power cycle using air as the working substance, the temperature and pressure at the end of the isentropic compression process are 1500 F and 800 psia, respectively. Tthe pressure at the beginning of the isentropic expansion is 120 psia. Sink temperature is 70 F. Determine
A the change of entropy for the heat addition process, Btu/lb. R
B. the heat added, Btu/lb
C. the cyde thermal effidiency, %
D. the available energy for the cycle, Btu/lb
Ans. 0.1300
Ans. 254.8
Ans. 73.0 %
Ans. 185.9
124
128. A reversed Carnot cycle rejects 833 Btu/lb as heat at a temperature of 1140 F. The gycle receives heat at a temperature of 140 F. Calculate
A. the change of entropy for the heat rejection process, Btu/Ib.R
B. the net cycle work, Btu/lb
Ans. (-)0.5206
Ans. (-)520.6 Btu/lb (on)
125
129. A six cylinder, two-stroke marine diesel engine operates at a piston speed of 1200 rpm. The 5 in x 5.6 in engine has an 18:1 compression ratio. If the air intake is at 14:8 psia and 82 F, determine A. the displacement volume, ft^3
B. the dearance
C. the ideal air inlet volumetric flow rate, ft^3/min
D. the mass flow rate for a volumetric efficiency of 85 %, lb/min
Ans. 0.3818
Ans. 0.0588
Ans. 458.2
Ans. 28.7
126
130. A six cylinder, two-stroke marine diesel engine operates at a piston speed of 1200 rpm. The 5 in x 5.6 in engine has an 18:1 compression ratio. if the air intake is at 14.8 psia and 82 F. It delivers 200 bhp and indicated power of 250 hp. Determine
A. Engine torque, ft.lbf
B. brake mean effective pressure, psi
C indicated mean effective pressure, psi
D. mechanical efficiency, %
E. friction power,fhp
Ans. 875
Ans. 89
Ans. 112
Ans. 79 %
Ans. 50
127
131. At the beginning of the compression stroke an ideal Otto cycle has an air pressure of 15 psia, a temperature of 75 F and a specific volume of 13.2 cubic feet per pound, At he end of compression the specific volume is 1.76 cubic feet per pound. The heat supplied to the cycle is 352 Btu/lb. Calculate
A. the compression ratio
B. the highest temperature and pressure of the cycle
C. the temperature and pressure at the end of expansion of the air
D. the heat rejected, Btu/lb
E. the net work of the cyde, Btu/lb
F. the thermal efficiency of the cycle,%
G. the horsepower developed by an ideal engine operating on this cycle using 0.5 pound of air per second
Ans. 7.5
Ans. 3256 R, 685 psia
Ans. 1454 R, 40.8 psia
Ans. 157
Ans. 195
Ans. 55.4%
Ans.138 hp
128
132 At the.beginning of compression an ideal Diesel oyele using air has a pressure of 15 psia, a temperature of 75 F and a specific volume of 13.2 cubic feet per pound. for a compression ratio of 15 and a heat addition of of 352 Btu per
pound, Calculate
A. the temperatures and pressures at the end of compression, at the end of expansion process
B. the heat rejected,Btu/lb
C. the network, Btu/lb
D. the thermal efficieny, %
E. the horsepower developed by an ideal engine operating on the cycle and using 0.5 pound per second air.
F. the thermal efficiency of a cycle having the same initial conditions and compression ratio, but with a constant
pressure heat addition of 500 Btu/lb
Ans. p2= 664.7 psia, T2 = 1580 R, p3= 664.7 psia, T3= 3047 R, T4 = 1341 R, p4 = 37.6 psia
Ans. 137.8
Ans. 214.2
Ans. 60.9%
Ans. 151.5 hp
Ans. 58.9%
129
133. At the beginning of compression an ideal dual combustion cycle using air has a pressure of 15 psia, a temperature of 75 F and a specific volume of 13.2 cubic feet per pound, For a compression ratio of 12 and a heat addition of 176 Btu per pound at constant volume and 176 Btu/lb at constant pressure, calculate
A. the temperatures and pressures at the end of isentropic compression.
B. the temperatures and pressures at the end of each heat addition process.
C. temperature at the beginning of heat rejection process, R.
D. the heat rejected, Btu/lb
E. the net work, Btu/lb
F. the thermal efficiency, %
G. the horsepower developed by an ideal engine operating on the cycle and using 0.5 pound per second air.
Ans. p2= 486 psia, T2 = 1446 R
Ans. p3= 832 psia, T3= 2475 R, T4= 3208 R, p4= 832 psia
Ans. T5= 1317 R
Ans. 134
Ans. 218
Ans. 61.9%
Ans. 154.2 hp
130
134. A spark ignition engine operating at a given load produces an indicated power output of 190 ihp with a corresponding mechanical efficiency of 85%. The engine uses 26.2 lb of gasolinte during a 20 minute test run while consuming 18.5 lb of air per minute. The heating value of the gasoline used is 19,500 Btu/lb fuel. Calculate
A. the AF ratio, lb air/lb fuel
B. the indicated thermal efficiency, %
C the brake specific fuel consumption, lb fuel /bhp.hr
D. the engine friction power, fhp
Ans. 14.12
Ans. 32.4
Ans. 0.487
Ans. 28.4
131
135. A two-stroke compression ignition engine has 14 cylinders and a total engine piston displacement of 4500 cubic inches. While operating at a speed of 1620 rpm, it produces a continuous torque reading of 5960 ft-lbf. At this speed, the engine is found to have a brake specific fuel consumption of 0.61 lb fuel/bhp.hr. Find
A. the engine brake power,hp
B. the brake mean effective pressure, psi
C. the time required to burn 5000 gallons of fuel (fuel specific gravity = 0.84).
Ans. 1840 hp
Ans. 100 psi
Ans. 31.2 hr
132
136. A four-stroke compression ignition engine delivers 600 bhp of brake power output when running at 2400 rpm. The engine total piston displacement is 1650 cubic inches, and the overall AF ratio is 22 to 1. The engine requires 69.5 pounds of air per minute. Determine
A. the brake mean effective pressure, psi
B. the brake torque, ft-lbf
C. the brake specific fuel consumption, Ib fuel/bhp.hr
Ans. 120 psi
Ans. 1311 ft-lbf
Ans. 0.315 lb fuel/bhp.hr
133
137. An IC engine with an AF ratio of 13.5 to 1 uses a fuel with a heating value of 19,000 Btu/lb fuel. The unit produces a continuous brake power output of 450 bhp while consuming 90 lb of fuel during a 30-minute period of operation . From the engine performance, the indicated thermal efficiency is found to be 39 percent. Calculate
A. the mechanical efficiency in %.
B. the required air flow, lb air/min
C. the brake specific fuel consumption, lb fuel/bhp.hr
Ans. 85.9%
Ans. 40.5 Ib air/min
Ans. 0.4 lb fuel/bhp.hr
134
138. An IC engine uses 9.1 pounds of air per minute while operating at 1200 rpm. The engine requires 0.352 pound of fuel per hour to produce a unit indicated power output of 1 ihp. The AF ratio is 14 to 1, the indicated thermal efficiency is 38 percent, and the mechanical efficiency is 82 percent, Find
A. the brake power output, bhp
B. the heating value of the fuel used.
Ans. 90.9 bhp
Ans. 19,025 Btu/lb fuel
135
139. A twelve-cylinder four-stroke marine gasoline engine, with a 6.375 inch bore and 6.500 inch stroke, delivers 1200 bhp of brake power output when running at 2400 rpm. The engine produces an indicated power output of 1500 ihp while bumning 126.8 gallons of fuel per hour. The fuel has a density of.6.2 Ib/gallon. Determine
A. the brake mean effective pressure, psi
8. the brake specific fuel consumption, Ib fuel/bhp.hr
C the indicated mean effective pressure, psi
D. the mechanical efficiency, %.
Ans. 159 psi
Ans. 0.655
Ans. 198.8
Ans. 80 %
136
140. A Stirling cycle operating with air as a working substance has a pressure of 80 psia, a temperature of 250 F and a specific volume of 3.28 ft^3 /lb at the baginning of the isothermal heat rejection process, The ratio of volumes at the beginning and end of the isothermal heat rejection process is 2. The highest temperature involved in the cycle is 1200 F. Calculate:
A. the heat supplied, Btu/lb
B. the heat rejected, Btu/lb
C. the thermal efficiency of the cycle in %.
Ans. 78.8
Ans. 33.7
Ans 57.2%
137
141. An ideal Joule cycle using air operates with a maximum pressure of 600 kPa abs and a maximum temperature of 725 C At the beginning of the isentropic compression process, the pressure is 102 kPa abs and the temperature is 20 C. Calculate,
A. the heat supplied, KJ/kg
B. the heat rejected, KJ/kg
C. thermal efficiency of the cycle
Ans. 5143
Ans. 310.0
Ans. 39.7%
138
142 In an ideal Otto cycle, the temperature at the end of the heat addition process is 2600 F, and the temperature at the end of the expansion process is 883 F. What is the compression ratio?
Ans. 7.84
139
143. An Otto cycle, with a 7 to 1 compression ratio, has 320 Btu/lb of heat supply. At the beginning of the compression process the pressure and temperature are 14.7 psia and 60 F. Assuming constant specific heat, calculate
A. the peak temperature, F
B. the peak pressure, psi
C. the net work, Btu/lb
D. the thermal efficiency, %.
Ans. 2542
Ans. 595
Ans. 173
Ans. 54 %
140
144. In an ideal Otto cycle the pressure at the beginning of the compression process is 15 psia, the temperature is 70 F and the volume is 13.08 ft^3. The maximum temperature of the cycle is 2804 F, and the heat supplied is 372 Btu. Using constant specific heat, calculate
A. the temperature at the beginning of the combustion, R
B. the compression ratio
C. the temperature at the end of the expansion process, R
D. the net work of the cycle, Btu
E. the thermal efficiency of the cycle, %
Ans. 1089
Ans. 6.05
Ans. 1589
Ans. 191
Ans. 51.3 %
141
145. An ideal Otto cycle operates with a temperature of 370 C at the end of the compression process, a maximum temperature of 370 C at the end of the compression process, a maximum temperature of 1510 C and a minimum temperature of 20 C. What is the temperature at the beginning of the heat rejection process, C?
Ans. 539.5
142
146. In an ideal Otto cycle heat supplied is 920 KJ/kg and the highest temperature in the cycle is 1600 C. Calculate
A. the temperature at the end of the isentropic compression process, C.
B. the change of entropy of the heat rejection process, KJ/kg. K
Ans. 315
Ans. 0.829
143
147. At the beginning of the compression process in an ideal Diesel cycle the pressure is 15 psia, the temperature is 70 F and the volume is 6.54 ft^3 . The compression ratio for the cycle is 15, and the heat supplied is 188 Btu. At the end of compression process the pressure is 665 psia, and the temperature is 1108 F. Using constant specific heat, calculate
A. the maximnum temperature in the cycle, F
B. the temperature at the end of expansion process, F.
C. the heat rejected in Btu
D. the net work of the cycle, Btu
E. the thermal efficiency of the cycle, %
F. the horsepower of an engine operating on such a cycle using 0.5 lb of air/second.
Ans. 2675 F
Ans. 939 F
Ans. 74.3 Btu
Ans. 113.7 Btu
Ans. 60.5 %
Ans. 160.8 hp
144
148. In an ideal Diesel cycle the change of entropy for the heat rejection process is 0.1662 Btu/lb. R. The temperature and the pressure at the beginning of the isentropic compression are 75 F and 15 psia, respectively. Pressure at the end of isentropic compression process is 555 psia. Determine
A. the temperature at the beginning of the heat addition process, F
B. the highest temperature in the cycle, F.
Ans. 1040 F
Ans. 2540 F
145
149. A Diesel cycle has a 16 to 1 compression ratio and a peak cycle temperature of 2912 R. Conditions at the beginning of compression are 14.7 psia and 60 F. Assuming constant specific heat determine:
A. the peak pressure, psi
B. the heat supplied, Btu/lb
C. the net work, Btu/lb
D. the thermal efficiency, %.
Ans. 714
Ans. 320
Ans. 199
Ans. 62.2 %
146
150. A Diesel has a peak pressure of 745 psia. The conditions at the beginning of compression are 15 psia and 530 R. Heat added to the cycle is found to be 392 Btu/lb. Assuming constant specific heat find
A. the compression ratio
B. the net work in Btu/lb
C. the cut-off ratio
D. the thermal efficiency, %
Ans. 17 to 1
Ans. 227 Btu/lb
Ans. 1.9 to 1
Ans. 58 %
147
151. At the beginning of the isentropic compression process in an ideal dual combustion cycle the pressure is 15 psia, the temperature is 70 F and the volume is 0.5 ft^3, The compression ratio is 12 to 1, and the temperature after constant volume receipt of heat is 1800 F. During constant pressure heat receipt, 5 Btu are supplied to the cycle. Using constant spedific heat, calculate
A. the total heat added to the cycle, Btu
B. the heat rejected cycle in Btu
C the net work of the cycle, Btu
D. the thermal efficiency of the cycle, %
Ans. 10.4
Ans. 3.9
Ans.6.5
Ans. 62.5 %
148
152. In a dual combustion cycle the specific volume at the end of isentropic compression is 1.09 ft^3/lb and the highest temperature in the cycle is 2444 F. The heat supplied at constant volume is 100 Btu/Ib. At the beginning of the compression process, the pressure and temperature are 14.7 psia and 60 F, respectivel y. Assume constant specific heat and find
A. the compression ratio
B. the heat supplied to the cycle, Btu/lb
C the work, Btu/lb
D.' the thermal efficiency, %
E. the cut-off ratio
Ans. 12 to 1
Ans. 320 Btu/lb
Ans. 195.5
Ans. 61 %
Ans. 1.46
149
153. In an ideal Brayton cycie, air enters the compressor at 15 psia and 75 F. The ternperature of the air at turbine inlet is 1600 F. For a maximum theoretical net work, find
A the temperature of the air leaving the compressor, F
B. the pressure ratio
C. the net work, Btu/lb
D. the thermal efficieny
Ans. 590
Ans. 10.6
Ans.118.9
Ans. 49 %
150
154. Determine
A. the best intercooler pressure
B. the work required per kilogram of air for an ideal two stage compressor operating between the suction pressure of 105 kpa abs and a discharge pressure of 1260 kpa abs. The suction temperature is 25 C.
Ans. 363.7 Kpa abs
Ans. (-)255.2 KJ/kg
151
155. An axial flow compressor discharges 900 lb/min of air. Inlet conditions are 14.7 psia and 50 F, while the actual discharge conditions are 162 psia and 648 F. Calculate
A. the capacity, ft^3/min
B. the isentropic compression efficiency
C. the isentropic compression power, hp
D. the actual compression power, hp
Ans. 11,557 ft^3/min
Ans. 84 %
Ans. (-)2558 hp (on)
Ans. (-)3045 hp (on)
152
156. A 2 KW centrifugal compressor operates with suction conditions of 100 kPa absolute and 25 C. The pressure ratio for the unit is 3 and isentropic compression efficiency is 70 %. Determine
A. the discharge pressure
B. the discharge temperature (actual)
C. the work input per kg of air
Ans. 300 kPa abs
Ans. 455 K
Ans. (-)157.8 KJ/kg
153
157. A split shaft marine gas turbine has a power turbine rated at 15,000 internal horsepower. Typical operating conditions for the unit are: compressor inlet 14.5 psia and 60 F; compressor discharge 174 psia and 716 F, compressor turbine inlet 171 psia and 1630 F and power turbine exhaust 14.8 psia and 760 F. The compressor turbine at the above rating has an 85 % isentropic turbine efficiency. For these rated conditions, calculate
A. the compressor isentropic efficiency,%
B. the compressor turbine discharge pressure and temperature, psia, R
C. the power turbine isentropic efficiency,%
D. the compressor turbine power output,hp
E. the cycle thermal efficiency
Ans. 82.0 %
Ans. 1434 R, 34.06 psia
Ans. 70.4%
Ans. 45,980 hp (by)
Ans. 23. 4%
154
158 An ideal two-stage air compressor with an intercooler takes in air at 14.5 psia at 60 F and delivers it at 500 psia. The temperature of the air leaving the intercooler is 60 F. Calculate
A. the intermediate pressure for minimum total work, psia
B. the work required per pound of air delivered if compression is isentropic, ft-bf/lb
C the work required for isentropic single stage compression between upper and lower pressures specified, ft-lbf/b.
Ans. 85.2 psia
Ans. (-)127,899 ft-bf/lb
Ans, (-)169,800 ft-lbf/lb
155
159. A centrifugal air compressor has a pressure ratio of 3 and inlet conditions of 27 C and 103 kPa abs. The mass flow rate is 5 kg/sec measured at inlet. For isentropic compression, find
A. the discharge temperature,K
B. the discharge pressure, kPa
C. the required intemal power, KW
Ans. 410.6 K
Ans. 309 kPa
Ans. 555 KW
156
160. An axial air compressor with an isentropic compression efficiency of 83 % has an internal power of 65 hp and an overall pressure ratio of 10. Inlet conditions are 14.6 psia and 60 F. Determine
A. the discharge pressure, psia
B. isentropic discharge temperature, R
C. the actual discharge temperature, R
D. the mass filow rate, lb/min
E. the capacity, ft^3/min
Ans. 146
Ans. 1004
Ans. 1103
Ans. 19.7
Ans. 260
157
161. A centrifugal air compressor having an isentropic compression efficiency o f 78 % has inlet and discharge pressure of 100 kPa abs and 350 kPa abs, respectively, inlet temperature to the unit is 25 C , and the capacity measured at inlet is 1.0 m^3/sec. Determine
A. the pressure ratio
B. the actual discharge temperature, K
C. the mass flow rate, ke/sec
D. the intemal compressor power, KW
Ans. 3.5
Ans. 462
Ans. 1.17
Ans. 193
158
162. An axial air compressor having 33,000 hp of internal power has inlet condition of 14.5 psia and 65 F and discharge conditions of 160 psia and 647 F. Calculate
A. the pressure ratio
B. the isentropic discharge temperature, R.
C. the isentropic compression efficiency, %
D. the mass filow rate of air, lb/min
E. the capacity of the unit, ft^3/min
Ans. 11
Ans. 1042
Ans. 89 %
Ans. 10,110
Ans. 135,500
159
163. A Brayton cycle with a pressure ratio of 6 has compressor inlet conditions of 70 F and 14.7 psia. The turbine inlet temperature is equal to 1500 F. Calculate
A. the isentropic compressor discharge temperature, R
B. the isentropic turbine discharge temperature, R
C the thermal efficiency of the basic cycle, %
D. the thermal efficiency of the cycle used as an ideal regenerative cycle, %
Ans. 884.3 R
Ans. 1174.7 R
Ans. 40.1 %
Ans. 54.9 %
160
164. A Brayton cycle with a pressure ratio of 6 has compressor inlet conditions of 70 F and 14.7 psia. The turbine inlet temperature is equal to 1500 F. The basic cycle is to be modified by adding ideal reheat. Calculate
A. the HP turbine discharge pressure, psia
B. the HP turbine discharge temperature, R
C. the thermal efficiency of the ideal reheat cycle, %
Ans. 36.0 psia
Ans. 1517.4 R
Ans. 35.0 %
161
165. A gas turbine operating in an ideal open cycle is served by a compressor which receives air at 15 psia, 80 F and13.32 ft^3/Ib and delivers it to the combustion chamber at 60 psia. In the combustion chamber 300 Btu are added at constant pressure to each pound of air flowing. Steady flow conditions exist throughout the cycle. Using constant specific heat, calculate
A. the compressor work, Btu/lb
B. the turbine work, Btu/lb
C. the net cycle work, Btu/lb
D. the cycle thermal efficiency, %
E. the net power delivered by this cycle when using 36.2 lb of air
162
166, An open Brayton cycle using air operates with a maximum cycle temperature of 1300 F and pressure ratio is 6.0. Heat supplied in the combustion charnber is 200 Btu/lb. The ambient temperature of
compressor is 95 F, and the atmospheric pressure is 14.7 psia. Using constant specific heat, calculate
A. the maximum pressure of the cycle, psia
B. the temperature of the air leaving the turbine, F
C. the cycle thermal efficieny, %
Ans. 85.0
Ans. 595
Ans. 40.0 %
163
167. The following data were obtained during performance test with a simple open cycle gas turbine engine: compressor inlet temperature, 520 R; compressor isentropic discharge temperature, 672 R; actual compressor discharge temperature, 691 R; turbine inlet temperature, 1500 R; turbine isentropic discharge temperature, 1184 R; and turbine actual discharge temperature, 1216 R. For these conditions calculate
A. the compressor isentropic efficiency
B. the turbine isentropic efficiency
C. the net cyde work, Btu/lb
D. the thermal efficiency
Ans. 88.9%
Ans. 89.9%
Ans. 27.12 Btu/lb
Ans. 13.96 %
164
168. The following performance data were generated by a gas turbine having intercooling: LP compressor inlet conditions of 14.7 psia and 520 R; LP compressor isentropic discharge temperature, 743.8 R, compressor isentropic efficiency, 78 percent; HP compressor inlet temperature, 520 R; HP compressor isentropic discharge temperature, 743.8 R, HP compressor isentropic efficienoy, 82 %; turbine inlet temnperature, 2000 R; and turbine isentropic efficiency, 90 %. Calculate
A the LP compressor actual discharge temperature, R
B. the HP compressor actual discharge temnperature, R
C. the turbine actual discharge temperature, R
D. the net cycle work, Btu/lb
E. the thermal efficiency, %
Ans. 806.92
Ans. 792.93
Ans. 1079.79
Ans. 86.49
Ans. 29.85 %
165
169. The following performance data were obtained for a gas turbine engine having ideal reheat: comnpressor inlet conditions of 14.7 psia and 520 R; HP turbine inlet temperature, 2550 R, HP turbine isentropic discharge temperature, 2237 R; LP turbine inlet temperature, 2550 R; and LP turbine isentropic discharge temperature, 2237 R. For these conditions, calculate
A. the turbine pressure ratio
B. the HP turbine discharge pressure, psia
C. the compressor isentropic discharge temperature, R
D. the net cycle work, Btu/lb
E. the thermal efficieny
Ans. 2.4535
Ans. 88.49
Ans. 2505.1 R
Ans. 168.26
Ans. 69.75
166
170 A gas turbine operating in an ideal open cycle is served by a compressor which receives air at 15 psia, 80 F, and delivers it to the combustion chamber at 60 psia. Three hundred Btu are added at constant pressure to each pound of air in the combustion chamber. Using air tables, calculate
A. the compressorwork, Btu/Ib
B. the turbine work, Btu/lb
C. the net work, Btu/lb
D. the thermal efficiency, %
E. the net power for an air supply of 36.1 lb/sec, hp
Ans. 63.0
Ans. 156.7
Ans. 93.7
Ans. 31.23 %
Ans. 4784 hp
167
171. A split-shaft gas turbine has its power unit receiving 140 Ib/sec of combustion products at 45 psia and 1600 R. Exhaust temperature and pressure for the power turbine are 1245 R and 0.2 in Hg gauge. Barometric pressure is 29 in Hg absolute, while ambient temperature is 59 F. Using the air tables determine
A. the isentropic turbine outlet temperature, R
B. the isentropic turbine work, Btu/Ib
C. the actual turbine work, Btu/lb
D. the isentropic turbine effidency, %
E. the turbine internal power, hp
Ans. 1194
Ans. 106.0
Ans. 92.9
Ans. 87.7 %
Ans. 18,400 hp
168
172. A marine split-shaft gas turbine has its power turbine supplied with 150 lb/sec of gas at 50 psia and 1100 F and exhausts the gas from tHe power turbine at 16 psia and 800 F, respectively. The power turbine exhaust is led through a counterflow regenerator where the gas temperature is lowered another 40 F. The compressor pressure ratio is 12.0, and the compressor inlet conditions are 14.6 psia and 60 F, Calculate
A. the power turbine efficiency, %
B. the compressed air temperature leaving the regenerator, F
C. the regenerator effectiveness, %
Ans. 74.5%
Ans. 780
Ans. 66.7%
169
173. Brayton cycle aircraft gas turbine engine has an axial flow compressor which provides a pressure ratio of 10 to 1. Material design conditions limit the temperature of the working substance entering the turbine to 2200 F. The engine is designed to handle 90 lb of air/sec at static conditions and 120 lb/sec at a flight speed of 400-knots when sea level ambient pressure and temperature are 15.0 psia and 530 R, respectively. Estimate
A. The sea level static thrust, lbf
B. the thrust, lbf
C. the propulsive efficiency, %, for a flight speed of 400 knots at sea level (1 knot= knot = 1.69 ft/sec)
Ans.7300
Ans. 7559
Ans. 40 %
170
174. A Brayton cycle aircraft gas turbine has an axial flow compressor providing a pressure ratio of 12 to 1. Material design conditions limit the temperature of te working substance entering the turbine to 2000 R. The engine is designed to handle 90 lb of air/sec at static conditions and 120 lb/sec at a flight speed of 500 knots when sea level ambient pressure and temperature are 15.0 psia and 530 R, respectively. Estimate
A. the sea level static thrust, Ibf
B. the thrust, lbf.
C. propulsive efficiency, %
D. cyde thermal efficiency, %, for a flight speed of 500 knots at sea level.
When equipment for afterbuming, nozzie inlet temperature is limited to 2500R. Assuming all stated performance parameters remain constant, estimate
E. the thrust, lbf
F. the thermal efficiency, % with afterburning For a flight speed of 500 knots at sea level.
Ans. 6635
Ans. 6045
Ans. 51%
Ans. 55.8 %
Ans. 9180
Ans. 44.5 %
171
175 A Rankine steam power cycle operates with steam at 600 psia and 850 F from the boiler and a condenser pressure of 1 inch of mercury absolute. Enthalpies are h4 = 49.4 Btu/lb, h1 = 1435.4 Btu/lb, s1 = s2 = 1.6559 Btu/Ib. R, h2= 890.0 Btu/lb, h3 = 47.1 Btu/lb, s4 = s3 = 0.09146
Determine
A. the pump work, Btu/lb
B. the heat supplied, Btu/lb
C. the heat rejected, Btu/Ib
D. the net work, Btu/lb
E. the turbine work, Btu/Ib
F. the thermal efficiency,%
Ans. 2.3
Ans. 1386.0
Ans. 842.9
Ans. 543.1
Ans. 545.4
Ans. 39.2 %
172
176. An ideal Rankine reheat cycle operates with steam at 1200 psia and 1060 F from the boiler. After expansion in the turbine to 90 psia, the steam is returned to the boiler and reheated to a temperature of 950 F. Condenser pressure is maintained at one inch of mercury absolute. h1 = 1534.7 Btu/lb, h2 = 1219.3 Btu/lb, h3 = 1506.5 Btu/lb, h4 = 1029.0 Btu/lb, h5 = 47.1, h6 = 51.2 Btu/lb
Calculate
A. pump work
B. heat added
C. heat rejected
D. turbine work
E. net cycle work
F. cyde thermal efficiency
Ans. 4.1
Ans. 1770.7
Ans. 981.9
Ans. 792.9
Ans. 788.8
Ans. 44.5%
173
177. A geared turbine marine propulsion unit delivers 35,000 shaft horsepower at full power with a shaft speed of 240 rpm. The mechanical efficency of the unit under these conditions is 95 %. At 122 rpm the unit delivers 4750 hp, receiving steam at the throttle at 1250 psia and 940 F at the rate of 32,150 lb/hr and exhausting to a condenser at 0.7 psia. Assuming the mechanical losses vary as the square of the rotative speed, find for the 122 rpm conditions:
h1 = 1462.6 Btu/lb, h2 = 876.0 Btu/lb
A. the estimated mechanical loss, hp
B. the mechanical effliciency, %
C. the shaft engine afficiency, %
D. the Internal angine efficiency, %
Ans. 475
Ans. 90.9
Ans. 64.1
Ans. 70.5
174
178. In a Rankine Gyle, steam enters the turbine at 750 psia and 800 F. The condenser pressure is 1 psia. Find
A. the moisture content of the steam entering the condense
B. the turbine work, Btu/lb
C. the pump work, Btu/lb
D. the heat supplied, Btu/lb
E. the heat rejected, Btu/Ib
F. the net work of the cycle, Btu/lb
G. the thermal efficieny, %
Ans. 20.2 %
Ans. 503.9
Ans. 2.3
Ans. 1328.6
Ans. 827.0
Ans. 501.6
Ans. 37.8 %
175
179. A Rankine cycle has a boiler pressure of 1200 psia and a condenser pressure of 1.0 in of Hg abs, and temperature of the steam entering the turbine is 1000 F. Calculate
A. the rnoisture content of the steam entering the condense .
B..the turbine.work,Btu/|b
C. the pump work, Btu/lb
D. the heat supplied, Btu,/lb
E. the heat rejected,Btu/lb
F. the thermal efficieny,%
Ans. 21.0 %
Ans. 623.9
Ans. 4.1
Ans. 619.8
Ans. 828.7
Ans. 42.8 %
176
180. A Rankine steam power cycle operates with a top pressure of 8,274 kPa abs and a top temperature of 593 C. Condenser pressure is 6.895 kPa. Calculate for the cycle, in KJ/kg,
A. the heat added
B. the heat rejected
C. the net work
D. the pump work
E. the cyde thermal efficiency
Ans. 3453 KJ/kg
Ans. 2006 KJ/kg
Ans. 1447 Kl/kg
Ans. 8.6 KJ/kg
Ans. 41.9 %
177
181. Heat is added to the working substance in an ideal Rankine cycle between the states of a compressed liquid at 1000 psia and 60.54 F and superheated steam at 1000 psia and 1000 F. For the cycle determine:
A. the heat added
B. the heat rejected from the cyde for a condenser temperature of 60 F, Btu/lb
C- the available energy for the cyde
Ans. 1474.5 Btu/lb
Ans. 830.2 Btu/lb
Ans. 644.3 Btu/lb
178
182 Sketch on T-s and h-s coordinates a Rankine steam power cycle and label the process lines and intersection points correspondingly. Then, using an exhaust pressure of 2.0 psia, a heat addition pressure of 1200 psia and a maximum cycle entropy of 1.7040 Btu/lb.R, determine the enthalpies at the four process intersection points, Btu/lb.
Ans. h4 = 98.1, h1 = 1615.5, h2= 989.7, h3= 94.0
179
183. A Rankine steam power cycle has a heat addition process pressure of 1000 psia and maximum steam temperature of 800 F. Condenser pressure is 1.0 psia. Calculate
A. the pump work, Btu/lb
B. the heat added, Btu/lb
C. the heat rejected, Btu/lb
D. the net cyde work, Btu/Ib
D. the cycle thermal efficiency, %
F. the power output of such a cycle when circulating 20 lb/sec of steam, hp.
Ans. 3.1
Ans. 1315.7
Ans. 805.1
Ans. 510.6
Ans. 38.8 %
Ans. 14,444
180
184. In an ideal reheat cycle, steam enters the high pressure turbine at 750 psia and 800 F and leaves at 100 psia. It is then reheated to 800 F, passes through the low pressure turbine and exhausts to a condenser at 1 psia. Find
A. the moisture content of the steam entering the condenser
B. the pump work, Btu/Ib
C. the work of high pressure turbine, Btu/lb
D. the total turbine work, Btu/lb
E. the heat supplied, Btu,/Ib
F. the heat rejected, Btu/Ib
G. the net work of the cycle
H, the thermal efficiency, %
Ans. 7.2 %
Ans. 2.3
Ans. 211.11
Ans. 609.6
Ans. 1568.7
Ans. 961.4
Ans. 607.3
Ans. 38.7 %
181
185. In an ideal reheat cycle the pressure and temperature entering the high pressure turbine are 1200 psia and 1000 F, the reheat pressure is 72 psia, the reheat ternperature is 800 F and the condenser pressure is 1.0 inch of mercury absolute. Determine
A. the high pressure turbine work, Btu/lb
B. the moisture content of the steam entering the condenser, %
C. the low pressure turbine work, Btu/lb
D. the pump work, Btu/lb
E. the net work of the cycle, Btu/lb
F. the heat added to the cycle, Btu/lb
G. the heat rejected to the condenser, Btu/lb
H. the thermal efficiency of the cycle, %
Ans. 318.2
Ans. 8.0 %
Ans. 418.6
Ans. 4.1
Ans. 732.7
Ans. 1697.7
Ans. 965
Ans. 43.2 %
182
186. In an ideal regenerative cycle, steam is generated at 1200 psia and 1000 F. The condenser pressure is 1 inch of mercury absolute. Condenser only the pump work involved in pumping the total cycle flow from the single extraction
heater to the boiler. Calculate
A the optimum extraction pressure to the nearest pounds, psia
B. the mass of steam extracted, Ib/lb of throttle steam
C. the heat added to the cycle, Btu/lb
D. the heat rejected by the cycle, Btu/lb of throttle steam
E. the net cycle work, Btu/lb of throttle steam
F. the cycle thermal efficiency, %
Ans. 94
Ans. 0.2135
Ans. 1201.7
Ans. 651.8
Ans. 549.9
Ans. 45.8 %
183
187. Steam is generated in an ideal reheat-regenerative cycle at 1500 psia and delivered at 1050 F. After expansion in the turbine to the optimum pressure for a single extraction, the steam is removed from the turbine, one portion to
be used for feed water heating and the remainder to be rehtated to 960 F at the extraction pressure. Condenser pressure is 1 inch of mercury abs. Calculate
A. the optimum extraction pressure to the nearest pounds, psia
B. the mass of steam extracted, lb/lb of throttle steam
C. the heat added to the cycle, Btu/lb
D. the heat rejected by the cycle, Btu/lb of throttle steam
E. the net cycle work, Btu/lb of throttle steam
F. the cycle thermal efficiency, %
Ans. 114
Ans. 0.2244
Ans. 1438.3
Ans. 752.0
Ans. 686.3
Ans. 47.7 %
184
188. A Rankine steam cycle operates with steam leaving the superheater at 600 psia and 800 F. Condenser pressure for the cycle is 2 inch of mercury abs. Calculate
A. the pump work, Btu/lb
B. the temperature in the condenser, F
C. the turbine work, Btu/Ib
D. the heat added, Btu/b
E.. the thermal efficiency, %
F. the degrees of superheat of steam entering the turbine, F
Ans. 2.3
Ans. 79
Ans. 529.3
Ans. 1358.2
Ans. 38.8 %
Ans. 313.67 F
185
189. A Rankine reheat cycle operates with a top pressure of 600 psia, an entropy at the first superheater outlet of 1.6517 Btu/lb. R, a reheat pressure of 100 psia and an entropy at the condenser entrance of 1.8203 Btu/lb. R. Condenser pressure for the cycle is 1 inch of mercury abs. There is no pressure drop during reheating. Calculate
A. the pump work, Btu/lb
B. the high pressure turbine work, Btu/lb
C. the low pressure turbine work, Btu/lb
D. the heat added, Btu/lb
E. the heat rejected by the condenser
F. the thermal efficiency, %
Ans. 2.3
Ans. 202.3
Ans. 420.8
Ans. 1552.2
Ans. 931.4
Ans. 40.0 %
186
290. A modified Rankine reheat cycle (irreversible turbine expansion process) operates with a top pressure of 600 psia, an entropy at the first superheater outlet of 1.6067 Btu/lb. R an enthalpy leaving the high pressure turbine of
1210 Btu/lb, a reheat pressure of 100 psia (no pressure drop in reheater), and entropy at the entrance of the low pressure turbine of 1.8203 Btu/lb. R, a condenser pressure for the cycle is 1 inch of mercury abs and an enthalpy at the entrance to the condenser of 1050 Btu/lb. Calculate
A. the pump work, Btu/Ib
B. the total turbine work, Btu/Ib
C. the heat added to the steam, Btu/lb
D. the heat rejected by steam, Btu/lb
E. the cycle thermal efficiency, %
Ans. 2.3
Ans. 513
Ans. 1513.6
Ans. 1002.9
Ans. 33.7 %
187
191. A regenerative steam power cycle with a boiler pressure of 922.1 psia (saturation temperature 535 F) and a discharge temperature of 1000 F employs two stages of extraction for feed water heating . Condenser pressure is
0.9503 psia (saturation temperature 100 F). Steam removed at the first and second extraction points is designated m1 and my pounds per pound of throttle steam for these pressures, respectively. Determine
A. optimum extraction pressures, psia
B. the mass of steam removed at the first extraction point, lb/lb throttle steam
Ans. 220 psia, 27 psia
Ans. 0.1369
188
192. Sketch a Rankine steam power cycle on T-s and h-s coordinates; label the process lines and number the process intersection points correspondingly on both diagrams. Then sketch and number as equipment diagram to correspond
with the coordinate diagrams. Then calculate the thermal efficiency, %, for the cycle if it operates with high and low pressures of 1200 psia and 1.0 psia with a superheat temperature of 900 F.
Ans. 40.2 %
189
193. Steam is supplied to the throttle of a large turbine at 600 rpm and 800 F. The pressure drop from the throttle entrance to the steam chest is negligible. At the exhaust flange the absolute pressure is 0.7 psia and steam velocity is
400 ft/sec. The internal power developed is 20,000 hp and the steam flow is 135,000 lb/hr. Find
A the available energy, Btu/lb
B. the intemal turbine work, Btu/lb
C the intemal engine efficiency
D. the internal loss, Btu/lb
E. the enthalpy at the state line end point, Btu/lb
F. the required exhaust trunk cross-sectional area, ft^2
Ans. 531.5
Ans. 377.0
Ans. 70.9 %
Ans. 3.2
Ans. 1060.7
Ans. 42.1
190
194. An auxiliary turbo-generator set delivers 600 kW at the generator terminals. Steam is supplied to the throttle at 600 psia and 800 F. The exhaust pressure is 1.0 psia. The engine efficiency based on the generator output is 60 %. Find the steam flow through the turbine, lb/hr.
Ans. 6900 lb/hr
191
195. A marine geared turbine unit delivers 18,500 kW at the bull gear coupling at full power with a propeller shaft speed of 400 rpm. Under these conditions, the mechanical losses total 925 kW. At 35 km/hr, the propeller makes 200
rpm and the shaft power is 2000 kW. Assume the mechanical losses vary the square of the rpm and find:
A. the internal power developed at full power, kW
B. the mechanical efficiency of the unit at full power
C. the estimated mechanical loss power at 35 km/hr
D. the estimated mechanical efficiency at this speed
Ans. 19,425
Ans. 95.2 %
Ans. 231 kW
Ans. 89.6 %
192
196. A large turbine receives steam at the throttle at 1000 psia and 900 F, exhausting to a condenser at 1.5 in Hg abs. The brake output is 40,000 hp, and the mechanical losses amount to 800 hp.. The steam flow is 250,000 Ib/hr. Find
A. the available energy, Btu/lb
B. the brake work, Btu/lb
C the brake engine efficiency
D. the brake steam rate, lb/bhp.hr
E. the braķe heat rate, Btu/bhp.hr
F. the enthalpy of steam at the exhaust point, Btu/Ib
Ans. 562.8
Ans. 407.2
Ans. 72.4 %
Ans. 6.25
Ans. 8678
Ans. 1032.8
193
197. A refrigerating plant circulates 23 lb Freon-12 per minute and is assume to operate on a cycle . The pressure in the evaporator coil is 50 psia, the temperature of the Freon-12 entering the compressor is 50 F, the pressure in the condenser is 120 psia and the temperature of the liquid refrigerant entering the expansion valve is 86 F. Enthalpies are: h1 = 84.24 Btu/lb, h2 = 91.31 Btu/lb, h3 = h4 = 27.72 Btu/lb
Calculate
A. the refrigerating effect, Btu/lb
B. the capacity of plant, tons
C the power required to compress the Freon-12, hp
D. the coefficient of performance
Ans. 56.52
Ans. 6.5
Ans. 3.83
Ans. 7.99
194
198. A cooling plant using Freon-12 as the refrigerant is to have a capacity of 50 tons when operating on the refrigerant rating cycle. Enthalpies are: h1 = 80.04 Btu/lb, h2 = 91.13 8tu/lb, h3 = h4 = 25.56
For this ideal plant cycle determine
A. the refrigerating effect, Btu/lb
B. the rate of Freon-12 circulated, lb/min
C the net work required pef pound of Freon-12 circulated, Btu/lb
D. the coefficient of performance
E. the power required per ton of refrigeration, hp/ton
F. the heat rejected by the condenser, Btu/lb
G. the compressor piston displacement, ft^3/min.ton of refrigeration
Ans. 54.48
Ans. 183.6
Ans, 11.09
Ans. 4.91
Ans. 0.96
Ans. 12,040
Ans. 5.57
195
199. An air compression refrigeration system is to have an air pressure of 100 psia in the brine tank and an allowable air temperature increase of 60 F. For standard vapor compression cycle temperatures of 77 F entering the expansion
cylinder and 14 F entering the compression cylinder, calculate
A the coefficient of performance
B. the mass of air circulated per ton of refrigeration
C the required piston displacement of the compressor cylinder, neglecting volumetric efficiency.
Ans. 3.33
Ans. 13.9 lb/min.ton
Ans. 24.4 ft^3/min.ton
196
200. An ideal Freon-12 refrigerating system has a capacity of 50 tons. The condenser pressure is 180 psia, and the Freon-12 temperature leaving the condenser is 120 F. The pressure leaving the expansion valve is 44 psia, and the
temperature of the Freon-12 leaving the succeeding coil is 40 F. Circulating water enters the condenser at the temperature of 100 F and leaves at 115 F. Determine
A. the mass of Freon-12 circulated, lb/hr.
B. the compressor power for isentropic compression, Btu/lb
C. the heat capacity of the system, Btu/hr
D. the mass of water circulated through the condenser and heating system, lb/hr
E. the useful heat furnished per Btu of compressor work (Heating Performance Ratio)
Ans. 12,800
Ans. 144,400
Ans. 744,300
Ans. 49,620
Ans. 5.15
197
201. Calculate the horsepower required per ton of refrigeration produced by the reversal of a Carnot cycle having a thermal efficiency of
A. 50 percent
B. 25 percent
C. 12.5 percent
Ans. 4.71 hp
Ans. 1.57 hp
Ans. 0.673 hp
198
202. A refrigerating plant for an air-conditioning system is to have a capacity of 10 tons and a coefficient of performance of 2.50 when operating with a refrigerating effect of 61.4 Btu/lb of refrigerant. Calculate
A the refrigerant flow rate, lb/min
B. the work done on refrigerant by the compressor, Btu/lb
C the compressor internal horsepower, hp
D. the rate of heat rejection from the system, Btu/min
Ans. 32.6
Ans. 24.6
Ans. 18.9
Ans. 2800
199
203. A refrigeration system has a capacity of 25 tons and rejects heat at the rate of 6560 Btu/min. Calculate
A. the rate of heat absorption by the refrigerant, Btu/min
B. the power required as input to te system, Btu/min
C. the coefficient of performance for the system
Ans. 5,000
Ans. 1560
Ans. 3.2
200
204. A modifed Rankine refrigerating cycle operates with an evaporator pressure of 21.4 psia and a condenser pressure of 141 psia. Refrigerant is Freon-12 circulating through the system at 30 lb/min. Liquid refrigerant at 141
psia and 100 F enters the expansion valve, and superheated vapor at 21.4 psia and 5 F enters the compressor.
Calculate
A. the refrigerating effect, Btu/lb
B. the plarrt capacity in ton of refrigeration
C. the power required to compress the refrigerant, hp
D. the plant coefficient of performance
Ans. 47.86
Ans. 7.18
Ans. 10.66
Ans. 3.17
201
205. A Freon-12 refrigerating unit for an air-conditioning system has an evaporation pressure of 60 psia and a condensing pressure of 110 psia. The temperature of the Freon-12 entering the expansion valve is 80 F, the temperature of the vapor entering the compressor (at 60 psia) is 60 F and the enthalpy after compression is 90.18 Btu/lb. Calculate
A. the refrigerating effect, Btu/lb
B. the coefficient of performance
C. the mass of refrigerant circulated if the capacity of the unit is 10 tons, lb/min
D. the internal power required, hp
Ans. 59.05
Ans. 12.18
Ans. 33.9
Ans. 3.87
202
206. A Refrigerating system for an ice plant circulates 213.5 Ib Freon-12 per minute. The evaporation pressure is 30 psia, the condensing pressure is 110 psia, the Freon-12 temperature leaving the coil and entering the compressor is
20 F and the temperature entering the expansion valve is 80 F. The plant produces ice at 30 F from the fresh water at 55 F. Assume isentropic compression and calculate
A the enthalpies of the Freon-12 entering and leaving the freeze box and the enthalpy leaving the compressor, Btu/lb
B. the refrigerating effect, Btu/lb
C. the internal compressor work, Btu/lb
D. the coefficient of performance
E. the internal power required, hp
F. the refrigerating capacity of the plant, tons
G. the ice output of the plant for continuous operation, tons/day
Ans. 26.28 Btu/lb, 80.73 Btu/lb, 91.02 Btu/lb
Ans. 54.45
Ans. 10.29
Ans. 5.29
Ans. 51.8
Ans. 51.8
Ans. 50
203
207. A Freon-12 refrigerating unit was tested by circulating the low pressure refrigerant through a commercial water cooler, and the following data were obtained: Freon-12 pressure and temperature at compressor suction, 46 psia and 78.4 F, at compressor discharge, 131 psia and 160.4 F, at condenser inlet, 131 psia and 159.6 F, at condenser outlet, 131 psia and 97.6 F; at expansion valve, 129 psia and 96.4 F, entering water chiller, 50 psia and 38.3 F, leaving water chiller, 50 psia and 79.8 F; temperature of fresh water entering chiller, 91.4 F; leaving chiller, 69.2 F; Freon-12 flow rate, 21 lb/min; water flow rate, 56 lb/min; power to compressor motor, 5.8 kW; and motor and belt efficiency, 82 %.
Calculate
A the capacity of the unit as established by the Freon-12 measurements, tons
B. the capacity of the unit as determined from the fresh water measurements, tons
C the power input to the unit at the compressor shaft, Btu/min
D. the shaft input per ton of refrigeration based on Freon-12, hp
E. the coefficient of performance based on Freon-12 capacity and compressor shaft input
Ans. 6.13
Ans. 6.21
Ans. 270.5
Ans. 104 hp/ton
Ans. 4.5
204
208. In an ideal (reversed Joule cycle) air-refrigerating system the temperature of the air entering the compression cylinder is 50 F, the temperature entering the after-cooler is 160 F and the temperature entering the brine tank is 0 F.
Calculate
A the temperature of the air leaving the after-cooler, F
B. the coefficient of performance
C. the mass of air which must be circulated per ton of refrigeration, lb/min
Ans. 99 F
Ans. 4.54
Ans. 16.7 lb/min
205
209. Air enters an ideal nozzle at a pressure of 60 psia with a temperature of 1340 F. The pressure at the nozzle exit is 15 psia. Determine the increase of kinetic energy of 1 lb of air produced by an isentropic expansion through the
nozzle.
Ans. 141.4 Btu/lb
206
210. Air enters an ideal nozzle at a pressure of 60 psia with a temperature of 1340 F, The pressure at the nozzle exit is 15 psia. What is the velocity of air leaving the nozzle, ft/sec?
Ans. 2662 ft/sec
207
211. Helium with k = 1.66, at a temperature of 130 C is flowing at a local speed of 1500 m/sec. Determine the following:
A. the local sonic velocity, m/sec
B. the local Mach number
C if the flow is sonic or supersonic
Ans. 1179.6
Ans. 1.272
Ans. Supersonic
208
212. Helium has a value of k= 1.66. For a Mach number equal to 1.0, deterine:
А. To/ T
B. P/ Po
C. W/ Wo
Ans. 0.7519
Ans. 0.4881
Ans. 0.6494
209
213. Air at a pressure of 60 psia with a temperature of 1340 F is to be expanded isentropically to a pressure of 15 psia in an ideal nozzle. Pc/P1= 0.53. Calculate or determine
A. the type of nozzle required
B. the critical velocity, ft/sec
C. the mass rate of flow for a minimum nozzle diameter of 0.50 in, lb/min
D. If the nozzle requires a diverging section, determine the maximum exit velocity developed in the nozzle, ft/sec
E. the required exit diameter in inches
Ans. Convergent-divergent
Ans. 1896 ft/sec
Ans. 8.9
Ans. 2661
Ans. 0.553 in
210
214. The nozzles of a gas turbine receive air at a pressure of 54 psia with a temperature of 1480 F and discharge to the impulse blades at a pressure of 18 psia. For a nozzle velocity coefficient of 0.97, calculate
A. the air velocity leaving the nozzles, ft/sec
B. the corresponding nozzle efficiency, %
C. the kinetic energy delivered to the turbine blades, Btu/lb
Ans. 2432
Ans. 94.1 %
Ans. 118
211
215. A converging-diverging nozzle receives steam at a pressure of 380 psia with a temperature of 480 F and expands it to a pressure of 50 psia. Assuming a velocity coefficient. of 0.98 for the supersaturated throat condition and an overall nozzle efficiency of 92 percent. From Steam Tables for a pressure of 380 psia and a temperature of 480 F: h1= 1234.4 Btu/lb, S1= 1.5220 Btu/lb. R
Calculate
A the actual throat velocity, ft/sec
B. the mass rate of flow for throat diameter of 0.50 in, Ib/min
C. the actual kinetic energy available at the nozzle exit, Btu/lb
D. the actual nozzle exit velocity, ft/sec
E. the required nozzle exit diameter, in
F. the length of the divergent section of the nozzle, inches, for an included angle of 12 degrees between the nozzle sides.
Ans. 1582 ft/sec
Ans. 60.1 Ib/min
Ans. 148. 5 Btu/lb
Ans. 2727 ft/sec
Ans. 0.720 in
Ans. 1.05 in
212
216. Air enters an ideal converging-diverging nozzle at a pressure of 73.5 psia with a temperature of 1400 F and negligible approach velocity. For isentropic expansion to an exit pressure of 14.7 psia, calculate:
A. the temperature of the air leaving the nozzle, F.
B. the kinetic energy of the air leaving the nozzle, Btu/lb
C. the velocity of air leaving
Ans. 714 F
Ans. 164.6 Btu/lb
Ans. 2870 ft/sec
213
217. The pressure of air entering an ideal convergent nozzle is 73.5 psia, the temperature is 1400 F and the velocity of approach is negligible. The nozzle discharges against a pressure of 14.7 psi. What is the nozzle exit velocity when expansion in the nozzle is isentropic, ft/sec?
Ans. 1930 ft/sec
214
218. Air enters a convergent-divergent nozzle having stagnation consitions of 65 C and 285 kpa. The Mach number of the throat is 0.77. For isentropic expansion through the nozzle, calculate:
A the throat pressure, kPa
B. the throat temperature, K
C. the throat velocity, m/sec
Ans. 192.5
Ans. 302.2
Ans. 268.3
215
219. Air enters a convergent-divergent nozzle at a pressure of 73.5 psia with a temperature of 1400 F and negligible approach velocity. The nozzle throat area is 1.373 in^2 and the exit pressure is 14.7 psia. For isentropic expansion throughout the nozzle, calculate
A. the throat pressure, psia
B. the velocity in throat, ft/sec
C. the rate of air flow-through the nozzle, lb/sec
D. the exit area necessary for the isentropic expansion, in^2
Ans. 39.0
Ans. 1930
Ans 1.25
Ans. 1.854
216
220. A convergent-divergent nozzle receives air at 88.2 psia with a temperature of 1340 F and negligible approach velocity and expands it to a discharge pressure of 14.7 psia. if the nozzle efficiency is 94 percent, calculate:
A. the energy availab!e to the nozzle, Btu/lb
B. the actual change of enthalpy across the nozle, Btu/lb
C. the nozzle exit velocity, ft/sec
D. the nozzle velocity coefficient
Ans. 173.1
Ans. 162.7
Ans. 2855
Ans. 0.97
217
221. Air enters a diffuser of a jet engine with a velocity of 1800 ft/sec relative to the aircraft. The intake pressure is 1.05 psia and intake temperature is -70 F. Assuming isentropic compression in the diffuser, calculate
A. the sonic velocity at the inlet conditions, ft/sec
B. the inlet Mach number
C. the stagnation temperature, R
D. the stagnation pressure, psia
Ans. 968
Ans. 1.86
Ans. 659.8
Ans. 6.61
218
222. Air is accelerated by a convergent nozzle to sonic conditions at the exit. The exit conditions are 14.7 psia and 75 F, For a mass flow rate of 5 lb/sec. Calculate
A the exit velocity, ft/sec
B. the exit density, lb/ft
C. the nozzle exit diameter, in
Ans. 1134
Ans. 0.07423
Ans. 3.30
219
223. Air enters an ideal diffuser at a speed of 1500 ft/sec at 22 psia and 650 F. For an isentropic compression, calculate
A. the inlet Mach number
B. the stagnation temperature, R
C. the stagnation pressure, psia
D. the ratio of inlet to exhaust area necessary to reduce velocity to 15 ft/sec
Ans. 0.918
Ans. 1297.1
Ans. 38.0
Ans. 0.01476
220
224. Air is discharge from a convergent-divergent nozzle at a Mach number of 1.732, The exit pressure is 15 psia, and the temperature is 150 F. For isentropic expansion and a negligible inlet velocity, calculate
A the stagnation temperature, R
B. the stagnation pressure, psia
C the throat temperature
D. the throat pressure, psia
Ans. 976
Ans. 77.7
Ans. 814
Ans. 41.2 psia
221
225. A convergent nozzle receives steam at a pressure of 200 psia with a temperature of 480 F and negligible approach velocity and discharges against a pressure of 50 psia. The minimum nozzle area is 1.373 in^2. Assume isentropic expansion in the nozzle and calculate:
A. the temperature of the steam leaving the nozzle, F
B. the velocity of steam leaving the nozzle, ft/sec
C. the rate of steam flow through the nozzle, lb/sec
Ans. 358
Ans. 1660
Ans. 3.76
222
226. A convergent-divergent nozzle that has a throat area of 1.373 in^2 receives steam at a pressure of 200 psia with a temperature of 480 F and negligible approach velocity, and discharges against a pressure of 50 psia. Assume isentropic expansion through the nozzle and calculate
A. the temperature of steam leaving the nozzle, F
B. the rate of steam flow through the nozzle, lb/sec
C. the moisture of steam leaving the nozzle, %
D. the velocity of steam leaving the nozzle, ft/sec
Ans. 281
Ans. 3.76
Ans. 3.74
Ans. 2430
223
227. A group of turbine nozzles receives steam at 600 psia with a temperature of 800 F and discharges to the blades at a pressure of 300 psia. Assume a nozzle efficiency of 94 % and calculate
A. the energy available to the nozzles, Btu/lb
B. the kinetic energy of the steam leaving the nozzle group, Btu/lb
C. the nozzle reheat, Btu/lb
D. the velocity of steam entering the blades, ft/sec
E. the state of the steam entering the turbine blades, psia and F
Ans. 84.9
Ans. 79.8
Ans. 5.1
Ans. 2000
Ans. 300 and 624.3
224
228. A converging nozzle has steam at its inlet with stagnation properties of 580 psia and 530 F. Assume isentropic expansion-and the steam exit conditions to be saturated vapor, calculate
A. the exit velocity, ft/sec
B. the exit pressure, psia
C. the exit temperature, F
Ans. 1376
Ans, 381.3
Ans.440
225
229. Steam enters a convergent nozzle with negligible velocity at 500 psia and 700 F. The exit area of the nozzle has a 0.5 in diameter. The conditions of the throat are 275 psia and 560 F. Calculate
A. the available energy, Btu/lb
B. the nozzle efficiency, %
C. the mass flow rate, lb/sec
Ans. 67.5
Ans. 92.0 %
Ans. 1.15
226
230. A nozzle has a steam flow rate of 0.8 Ib/sec. The exit pressure and temperature are 40 psia and 300 F, respectively. The exit area of the nozzle is 0.45 in^2, and the nozzle efficiency is 92 %. Determine
A. the actual nozzle exit velocity, ft/sec
B. the inlet stagnation temperature, F
C. the inlet stagnation pressure, psia
Ans. 2826
Ans. 650
Ans. 238
227
231. In a simple impulse stage, steam leaves the nozzles with a velocity of 1200 ft/sec. the nozzle angle is 15 degrees. Assume the bucket entrance and exit angle are the same and that the bucket velocity coefficient is 0.88. The wheel speed is 580 ft/sec, and steam is supplied to the turbine at the rate of 6000 lb/hr. Find:
A. the required bucket entrance angle for the given conditions
B. the bucket work, ft.lbf/lb and Btu/lb
C. the power developed in the buckets, hp
D. the available energy to the buckets, ft.lbf/lb and Btu/lb
Ans. 28.2
Ans. 25.2
Ans. 59.4
Ans. 28.74
228
232. Steam enters a simple impulse bucket wheel with an absolute velocity of 450 m/sec and a relative velocity of 270 m/sec, it leaves the blades with a relative velocity of 230 m/sec and an absolute velocity of 105 m/sec. Find:
A. the bucket velocity coefficient
B. the available energy, KJ/kg
C. the bucket loss, KJ/kg
D. the unused kinetic energy at exit, KJ/kg
E. the diagram efficiency
Ans. 0.85
Ans. 101.25
Ans. 10.00
Ans. 5.51
Ans. 84.7 %
229
233. The impulse stage of a turbine receives steam at 220 psia with a temperature of 420 F when the stage pressure is 140 psia. Under these conditions the available energy to thie stage is 38.5 Btu/lb, the nozze-bucket efficiency is 85 % and the absolute blade entrance and exit velocities are 1350 ft/sec and 350 ft/sec, respectively. Assume the
stage efficiency is equal to the nozzle-bucket efficiency and calculate:
A. the enthalpy of steam after isentropic expansion to the stage pressure, Btu/lb
B. the enthalpy of the steam entering the blades, Btu/lb
C. the enthalpy of the steam leaving the blades, Btu/lb
D. the enthalpy of the steam leaving the stage if there is negligible carryover velocity, Btu/lb
E. the state of the steam leaving the stage, pressure (psia) and moisture (%)
Ans. 1131.3
Ans. 1183.4
Ans. 1184.7
Ans. 1187.1
Ans. 0.77 %
230
234. The first stage of a 50 percent reaction group receives steam with negligible approach velocity at a pressure of 300 psia with a temperature of 520 F. The available energy to the stage is 10 Btu/lb, the fixed blade efficiency is 96 %, the velocity coefficient for the moving row is 0.88, the reactive effectiveness is 90 %, and the relative inlet and absolute exit velocities are 146 ft/sec and 160 ft/sec, respectively. Assume that the stage efficiency is the same as the combined blade efficiency and calculate
A the steam velocity leaving the fixed blades, ft/sec
B. the relative exit velocity from the moving blades, ft/sec
C the stage work, Btu/lb
D. the combined blade efficiency, %
E. the enthalpy of the steam entering the succeeding stage, Btu/lb, for complete velocity carryover
Ans. 490 ft/sec
Ans. 492
Ans. 8.69
Ans. 86.9
Ans. 1260.2
231
235. In a simple stage, the blade speed is 150 m/sec and the nozzle angle is 18 degrees. The velocity of the steam leaving the nozzles ia 320 m/sec. The bucket entrance and exit angles are both 33 degrees. The bucket velocity coefficient is 0.89. Find
A the relative velocity entering the buckets, m/sec
B. the relative velocity leaving the buckets, m/sec
C the total change of velocity relative to and in the direction of motion of the buckets, m/sec
D. the bucket work, KJ/kg
E. the absolute exit velocity
Ans.184
Ans. 163.8
Ans. 291.7
Ans. 43.75
Ans. 90.1
232
236. Steam enters the buckets of a simple wheel at an absolute velocity of 1200 ft/sec and leaves with an absolute velocity of 245 ft/sec. The relative entering velocity is 640 ft/sec, and the relative exit velocity is 540 ft/sec
Determine
A. the available energy to the buckets, ft-lbf/lb
B. the bucket loss, ft-lbf/lb
C the unused kinetic energy in leaving jet, ft-bf/lb
D. the bucket work, ft-lbf/lb and Btu/lb
E. the diagrarn efficiency, %
F. the power developed by the buckets, hp, if steam is supplied at the rate of 5000 lb/hr
Ans. 22,360
Ans. 1830
Ans. 930
Ans. 19,600
Ans. 87.7
Ans. 49.5
233
237. Steam enters the nozzles of a simple impulse stage with negligible velocity at 190 psia and 500 F. the velocity of the steam leaving the nozzles is 1175 ft/sec, ard the stage pressure Is 140 psia. The steam leaves the buckets with an absolute velocity of 300 ft/sec and an enthalpy of 1245.5 Btu/lb. Assume the stage efficiency is equal to the nozzle-bucket efficiency and that there is negligible velocity carryover to the next stage. Find
A the available energy to the stage, Btu/lb
B. the nozzle efficiency, %
C..the nozzle reheat, Btu/lb
D. the blade reheat, Btu/lb
E. the exit reheat, Btu/lb
F. the enthalpy of the steam entering the next stage, Btu/lb
G. the stage work, Btu/lb
H. the diagram efficiency of the buckets
I. the nozzle-bucket efficiency
Ans. 29.8
Ans. 92.5
Ans. 2.2
Ans. 3.2
Ans. 1.8
Ans. 1247.3
Ans. 22.6
Ans. 82 %
Ans. 75.8 %
234
238. In a 50 percent reaction stage, the carryover velocity from the preceding stage is 55 m/sec, the stage available energy is 50 kJ/kg, the fixed blade (nozzle) efficiency is 0.94 and the fixed blade velocity coefficient is 0.90. Find the velocity of the steam leaving the fixed blades, m/sec.
Ans. 222.4 m/sec
235
239. In a turbine stage with 30 percent reaction, the steam enters the moving blades with a relative velocity of 350 ft/sec, the stage avallable energy is 25 Btu/lb, the reactive effectiveness is 0.90 and the moving blade velocity coefficient is 0.92. Find the relative velocity of the steam leaving the moving blades, ft/sec.
Ans. 665 ft/sec
236
240. Steam enters a 50 percent reaction stage in a low pressure turbine with negligible carryover velocity at 12.0 psia
and a moisture content of 0.06. The steam leaves the fixed blades with a velocity of 670 ft/sec. The relative velocities entering and leaving the moving blades are 230 ft/sec and 670 ft/sec, respectively. The steam at exit from the moving blades has an absolute velocity of 230 ft/sec and a pressure of 9.0 psia. Assume the combined blade efficiency and the stage efficiency are equal and find
A. the stage work, Btu/lb
B. the available energy to the stage, Btu/lb
C. the combined blade efficiency, %
Ans. 15.8
Ans. 19.2
Ans. 82.3 %
237
241. The rotative speed of a high pressure turbine at full power is 6000 rpm. The first stage is of the simple impulse configuration, and the nozzles receive steam at 900 psia and 900 F with negligible velocity. The pitch diameter of the first stage buckets is 30 inches and the nozzle angle is 17 degrees. Find
A. the blade speed, ft/sec
B. the ideal blade speed-steam speed ratio
C the corresponding absolute speed velocity of the steam leaving the nozzles, ft/sec
D. the enthalpy drop across the nozzles assuming an isentropic process, Btu/lb
E. the entropy and enthalpy of the steam leaving the nozzles, Btu/lb-R
Ans. 785
Ans. 0.478
Ans. 1642
Ans. 53.8
Ans. 1.6257
238
242. A typical furnace side wall is constructed of a 1 in layer of diatomaceous earth insulating block, and 2 % in high temperature insulating brick faced with 4 1/2 in firebrick with 1/8 in steel casting. Average values of thermal conductivities are: diatomaceous earth insulating block, 0.063; insulating brick, 0.62; firebrick, 4.0; and steel casting 26 Btu/hr.ft.F. Average film coefficients are 3.0 and 2.2 Btu/hr.ft^2.F for inner and outer surface film, respectively. The wall area is 50 ft^2, the average gas tamperature is 2100 F and the ambient air temperature is 100 F. Calculate
A. the heat transfer coefficient, U, for this furnace wall
B. the heat transferred by the wall because of conduction
Ans. 0.394 Btu/hr.ft^2.F
Ans. 39,400 Btu/hr
239
243. A typical furnace side wall is constructed of a 1 in layer of diatomaceous earth Insulating block, and 2 % in high temperature insulating brick faced with 4 1/2 in firebrick with 1/8 in steel casting. Average values of thermal conductivities are: diatomaceous earth insulating block, 0.063; insulating brick, 0.62; firebrick, 4.0; and steel casting 26 Btu/hr.ft.F. Average film coefficients are 3.0 and 2.2 Btu/hr.ft^2.F for inner and outer surface film, respectively. The wall area is 50 ft^2, the average gas temperature is 2100 F and the ambient air temperature is 100 F. Calculate the temperature at the interface between the insulating brick and diatomaceous insulating block.
Ans. 1500 F
240
244. A high temperature steam line is covered with two successive layers of insulation. The layer in contact with the pipe is 1 1/2 in thickness of asbestos for which k is 0.08 Btu/hr.ft.F. The asbestos is covered with a 1 inch thickness of
magnesia insulation, which has a value of k of 0.04. The internal pipe diameter is 2.90 in, the pipewall thickness is
0.30 in and k for pipe is 26 Btu/hr.ft.F. The steam temperature is 800 F, and the internal surface film coefficient is 40
Btu/hr.ft^2.F, while the ambient outer temperature is 100 F and the outer surface film coefficient is 1.2.Calculate
A. the value of U based upon the external area of the magnesia covering
B. the heat loss from the steam for a length of 180 feet of pipe, Btu/hr
Ans. 0.1659 Btu/lb.ft^2.F
Ans. 46,516 Btu/hr
241
245. Calculate the overall heat transfer coefficient for a tubular heat exchange wherein the liquid carried in the tubes is heated by steam which surrounds them. The tubes are 5/8 in. Admiralty metal with a wall thickness of 0.049 in. The steam surface film coefficient is 1250 Btu/hr.ft^2.F, k for Admiralty metal is 70 Btu/hr.ft.F and the liquid surface film coefficient is 20 Btu/hr.ft^2.F.
Ans. 16.61 Btu/hr.ft^2.F
242
246. The internal diameter of a boiler generating tube is 4 in and the wall thickness is 0.375 in. In operation the external surface film coefficient is 26 Btu/hr.ft^2.F, the internal film coefficient is 1700 Btu/hr.ft^2.F and 0.375 in thickness of scale having a conductivity of 0.6 Btu/hr.ft.F is deposited on the inner surface of the tube. The metal conductivity is 26 Btu/hr.ft.F, the furnace gas temperature is 2100 F and the temperature of the water is 500 F.
Calculate
A. the overall coefficient af heat transfer for the clean tube, Btu/hr.ft^2.F
B. the overall heat transfer coefficient transfer coefficient including the effect of the scale, Btu/hr.ft^2.F
C the external tube surface temperature before and after the scale has formed.
Ans. 24.69
Ans. 9.18
Ans. 579 F, 566 F
243
247. Calculate the rate of heat flow in Btu/hr, through a 10 in wall of solid concrete which is 20 ft long by 8 ft high. The thermal conductivity of concrete is 1.0 Btu/hr.ft.F, the external surface temperature is 5 F and the internal surface temperature is 45 F.
Ans. 7680 Btu/hr
244
248. A 10 in wall of solid concrete which is 20 ft long by 8 ft high. The thermal conductivity of concrete is 1.0 Btu/hr.ft.F, the external surface temperature is 5 F and the internal surface temperature is 45 F. The outside film coefficent is 6.0 and the inside air temperature is 77 F. Calculate
A. the overall heat transfer coefficient, Btu/hr.f^2.F
B. the rate of heat flow through the wall, Btu/hr
Ans. 0.60
Ans. 7630
245
249. The wall of a cold storage room consists of an inside finish of 1/2 in cement plaster ( k = 0.67), two layers of corkboard each 2 in thick (k = 0.03) and an outside layer of building tile. The value of U for the entire wall is 0.058, the internal air film coefficient is 1.65, the inner temperature is 20 F and the outside temperature is 80 F. Calculate
A. the thermal resistance of the wall per ft^2 of surface area
B. the corresponding resistance from the outside of the wall to the interface between the corkboard layers
C . the temperature at the interface between the the corkboard layers, F
D. the heat flow through the unit wall area, Btu/hr,ft^2
Ans. 17.24
Ans. 11.01
Ans. 41.7
Ans. 3.48
246
250. A main stream line is covered with a 2 1/2 in thickness of magnesia insulation. The actual internal diameter of the
pipe is 7.625 in; the pipe wall thickness is 0.50 in; the respective values of k for the pipe and for the insulation are 25
and 0.04 Btu/hr.ft.F; the steam and air film coefficients are 180 and 2.0 Btu/hr.ft^2.F, respectively; the steam temperature is 800 F and the air temperature is 90 F. Calculate
A. the overall heat transfer coefficient based on the external area of the insulation, Btu/hr.ft^2.F
B. the heat transferred per hundred linear feet of pipe, Btu/hr
Ans. 0.1428
Ans. 36,165
247
251. A refrigeration pipe line has an actual internal diameter of 1.38 in and a wall thickness of 0.14 in and is covered with a 2 in layer of molded cork insulation. The refrigerant vapor film coefficient is 90 Btu/hr.ft^2.F; the thermal conductivities of the pipe and of the insulation are 25 and 0.025 Btu/hr.ft.F, respectively; the air film coefficient is 2.0 Btu/hr.ft^2.F; the refrigerant temperature is 20 F and the air temperature is 80 F. Calculate
A. the overall heat transfer coefficient, Btu/hr,ft^2.F, based on the external area of the insulation
B. the heat transfer per linear foot of pipe, Btu/hr.ft
C the temperature of the external surface of the insulation, F
Ans. 0.0825 Btu/hr.ft^2.F
Ans. 7.34
Ans. 77.5
248
252. heat transfer by radiation is an important phenomenon at high temperatures in furnaces and internal combustion engines. Consider a one-square-foot black body plane surface at a temperature of 70 F. Calculate the heat transfer to the surface from another one-square-foot black body plane directly above and parallel to the first at temperatures of
A. 100 F
B. 500 F
C. 1500 F
D. 2000 F
Ans. 33.4 Btu/hr
Ans. 1325 Btu/hr
Ans. 25,250 Btu/hr
Ans. 62,850 Btu/hr
249
253. A counter-flow lubricating oil cooler with a net heat transfer area of 258 ft^2 cools 60,000 lb of oil per hour from a temperature of 145 F at inlet to 120 F at discharge. The temperatures of the cooling water are 75 F and 90 F, respectirely, and the specific heat of the oil is 0.50 Btu lb.F.Calculate
A. the value of the overall heat transfer coefficient under these operating conditions, Btu/hr-ft^2.F
B. the required area for a parallel flow device having the same capacity under identical operating conditions, ft^2
Ans. 58.4
Ans. 272.0
250
254. A steam superheater has a net transfer area of 1620 ft^2 and a design capacity of 221,000 lb of steam/hr when receiving saturated steam at 650 psia and discharging at 850 F with a pressure drop of not more than 25 psi through the heater. The design heat transfer coefficient is 30 Btu/hr.ft^2.F
In operation the superheater receives 220,000 Ib of saturated steam per hour at a pressure of 650 psia and discharges against a pressure of 630 psia with a temperature of 850 F when the flue gas temperatures at entrance and exit are 2100 F and 1430 F, respectively. Calculate the operating heat transfer coefficient using counter flow log mean temperature difference.
Ans. 29 Btu/hr.ft^2.F
251
255. A steam boiler economizer heats 160,000 Ib of water per hr from 250 F to 335 F at an average pressure of 700 psia. Flue gas enters the economizer at a temperature of.1400 F and leaves at a temperature of 800 F. The net heat transfer area is 3840 ft^2 and the design value of U is 8 Btu/hr.ft^2.F for a capacity of 253,000 Ib/hr at the temperatures given above. How does the heat transfer coefficient calculated for these operating conditions compare with the design value?
Ans. 4.66 Btu/hr.ft^2.F
252
256. A steam condenser with a heat transfer area of 23,500 ft^2 has a design value of U of 486 Btu/hr.ft^2.F for a log mean temperature difference of 32.4 and a design operating pressure of 2.5 in Hg abs. The water consumption at rated capacity is not to exceed 40,500 gpm with a temnperature rise of 18.3 F. Measured temperatures of fresh water at this flow rate during an acceptance test were 71.5 F and 90 F at entrance and exit, respectively, and the average condenser pressure was 2.45 in Hg abs, Assuming no sub-cooling of the condensate, calculate the overall heat transfer coefficient established by the acceptance test, and compare this with the manufacture's design value given above.
Ans. 609 Btu/hr.ft^2.F
253
257. An exhaust gas regenerator (counter-flow heat exchanger) for a marine gas turbine handles 1.8 kg/sec of air from its compressor and heats it by means of 1.88 kg/sec of hot exhaust gas. Exhaust gas enters the regenerator at 593 C and leaves at 310 C. Compressed air enters the regenerator at 266 C. For this temperature range a constant pressure specific heat for the exhaust has may be estimated at 1090 J/kg.C. Assume no heat transfer other than between the generator fluids. Calculate:
A. the energy exchanged as heat by the two fluids, KJ/sec
B. the air temperature leaving the generator, C
C. the log mean temperature difference for the exchanger, C
Ans. 579.92
Ans. 586.6
Ans. 19.5
254
258. A heat exchanger receives oil having a specific heat of 0.45 Btu/b.F and a temperature of 160 F at the rate of 40,000 Ib/hr. Fresh water at an initial temperature of 60 F flows through the apparatus at the rate of 120,000 lb/hr. Assume unlimited heat transfer area and calculate
A. the common temperature which the fluids will reach under parallel flow, F.
B. the heat transfer by the exchanger, Btu/hr
Ans. 73
Ans. 1,560,000
255
259. Calculate the heat transfer area required by a parallel flow oil cooler which removes 1,524,000 Btu/hr from the oil while cooling it from 160 F at inlet to 75 F at discharge, when the cooling water temperatures are 60 F and 72.7 F, respectively. U for the heater is 52 Btu/hr.ft^2.F.
Ans. 1132 ft^2
256
260. A performance test of a finned-tube air heater having a heating surface area of 24.12 ft^2 gave the following results: temperature of entering steam, 252 F, temperature of condensate, 252 F, temperature in calorimeter, 220 F; pressure in calorimeter, 14.696 psia; condensate, 10 lb; time to collect condensate, 8 min 35 sec; temperatures of air entering and leaving heater, 74.5 F and 86.5 F, respectively. Calculate the overall heat transfer coefficient established by the test, Btu/hr.ft^2.F.
Ans. 15.97
257
261. Steam enters a closed feed water heater with a quality of 95 percent at a pressure of 50 psia and leaves through the drain valve as a saturated liquid at this pressure. Feed water enters the heater at the rate of 160,000 lb/hr with a pressure of 700 psia and a temperature of 100 F and leaves at a temperature of 250 F with negligible change of pressure. The heat transfer coefficient for the heater based on external tube area is 500 Btu/hr.ft^2.F, and the water velocity entering the tubes is not to exceed 4 ft/sec. Calculate
A. the quantity of steam required by the heater, lb/hr
B. the heat transfer area required, ft^2
C. the number
D. length, in ft, of 5/8 in OD. Admiralty metal tubes required (the tube wall thickness is 0.049 in)
Ans. 27,353
Ans. 564.7
Ans. 118
Ans. 29.0
258
262. A fuel oil heater delivers 30,000 lb of oil/hr at a temperature of 156 F. The initial temperature of the oil is 72 F.
the specific heat is 0.50 Btu/lb.F and U for the heater is 40 Btu/hr.ft^2.F. The heater receives saturated steam at 350 F, and the condensate leaves the heater as saturated liquid at this temperature. Calculate
A. the log mean temperature difference, F
B. the required surface area, ft^2
C. the quantity of steam required for the operation of the heater, Ib/hr.
Ans. 233.5
Ans. 134.9
Ans. 1446
259
263. A superheater having a surface area of 1800 ft^2 receives saturated steam at 630 psia and discharges superheated
steam at a pressure of 600 psia with a temperature of 740 F. It is estimated that the maximum flow rate of flue gas through the heater will be 3000 lb/min with an entering temperature of 1200 F and an axit temperature of 760 F. For counterfow of steam and flue gas and specific heat of 0.26 Btu/lb.F for the gas, calculate
A the log mean temperature difference, F
B. the value of U for the heater, Btu/hr.ft^2F
C. the maximum quantity of superheated steam that can be produced by the heater, lb/hr
Ans. 355.6
Ans 32.17
Ans. 121,000
260
264. Steam enters the condenser of a marine main propulsion plant at 2 psia and a quality of 86 percent at the rate of 175,000 lb/hr and with a velocity of 800 ft/sec. It leaves the condenser as a saturated liquid without any change in pressure. The salt water inlet (injection) temparature is 75 F and the overboard temperature is 90 F. Sea water has a specific heat of 0.96 Btu/lb.F and a specific weight of 64 1b/ft^3. The injection and overboard velocities are substantially equal. Calculate
A. the energy rejection rate from the condensing steam, Btu/min
B. the flow of sea water in gpm
C. the log mean temperature difference, F
D. the overall heat transfer coefficient for an assumed heat transfer are of 6035 ft^2, Btu/hr.ft^2.F
Ans. 2,601,000
Ans. 21,111 gpm
Ans. 43.1 F
Ans. 600
261
265. A superheater receives 100,000 lb/hr of saturated steam at 1250 psia. The conditions at the superheater outlet are 950 F and 1200 psia. The gases of combustion enter the superheater tube bank at 2500 F and leave at 1890 F. Determine
A. the log mean temperature difference assuming parallel flow, F
B. the log mean temperature difference assuming counter flow, F
C. the required heat transfer area assuming the log mean temperature difference to be 1400 F and the overall heat transfer coefficient to be 25 Btu/hr.ft^2.F, ft^2.
Ans. 1375
Ans. 1430
Ans. 825
262
266. A gas turbine exhaust stack cooler drops the gas temperature from 1000 F to 600 F by means of a water cooling coil. Cooling water enters the coil at 60 F and leaves, after
a counter-flow passage, with a temperature of 180 F. If Cp for the gas is 0.26 Btu/lb.F, Calculate
A. the quantity of water required to cool properly 100 lb/sec of exhaust gas, lb/sec
B. the log mean temperature difference, F
C. the overall heat transfer coefficient for an exchanger area of 2000 ft^2, Btu/hr.ft^2. F
Ans. 86.7
Ans. 670.3
Ans. 27.93
263
267. Determine the volumetric analysis of a mixture which consists of 56 percent nitrogen, 12 percent carbon dioxide and 32 percent oxygen as calculated on a mass basis.
A. Nitrogen
B. Carbon dioxide
C. Oxygen
Ans. 61.11%
Ans. 8.34 %
Ans. 30.55 %
264
268. Calculate the mass of moisture, in pounds, contained in 4000 ft^3 of atmospheric air having a temperature of 90 F when the barometric pressure is 30.12 in Hg
A. If the air is saturated
B. If the RH is 50 % (P sat = 0.6988 psia)
C. What is the dew point of the atmosphere
265
269. It is desired to produce a mixture of helium (Cv= 0.75) and hydrogen (Cv= 2.44) which will have a specific heat of 1.0 Btu/lb.F at constant volume. What must be the volumetric percentage of helium?
Ans. 74.2 %
266
270. A gaseous mixtuxe has the following mass analysis: H2, 10 %; CO2, 5 %; N2= 85 % Cp for common gases at room temperature: O2 (Cp= 0.217); H2 (Cp = 3.42); N2 (Cp = 0.247);
CO (Cp = 0.243); CO2 (Cp= 0.205. Find
A. the specific heat at constant pressure, Btu/lb.F.
B. the volumetric analysis, %
C. the partial pressure of the N2 in psia if barometer is standard and the mixture is at barometric pressure, psia
Ans. 0.562
Ans. H2= 61.4 %, CO2= 1.4 %, N2= 37.2 %
Ans. 5.47 psia
267
271. A tank contains air at 50 psia. Air may be assumed to consist of 79.1 percent N2 and 20.9 percent O2 by volume. Calculate
A. the partial pressure due to oxygen, psia
B. partial pressure due to nitrogen, psia
Ans. 10.45
Ans. 39.55
268
272. A mass analysis of gases in a compartment shows the following: O2, 20 lb; N2, 140 lb; CO2;, 15 lb; H20, 4 lb. Find the volumetric analysis of the gases, %.
Ans. O2= 10.10 %; N2 = 80.81 %; CO2 = 5.50 %; H20 = 3.59 %
269
273. The volumetric analysis of a gaseous mixture is as follows: CO2= 12 %, O2= 2 %, N2= 86 %. Find the mass analysis, %.
Ans. CO2 = 17.60 %, O2 = 2.13 %, N2= 80.27 %
270
274. Given, for atmospheric air: temperature, 82 F; barometric pressure, 29.95 in Hg; partial pressure of water vapor, 0.3632 psia. What is the dew point temperature?
Ans. 70 F
271
275. A room 14 ft x 16 ft x 10 ft contains atmospheric air at 72 F. The partial pressure of the water vapor in the air is 0.2140 psia. Barometer is standard. Calculate:
A. the mass of dry air in the room, lb
B. the mass of water vapor in the room, lb
C. the dew point temperature, F
Ans. 164.7
Ans. 1.51
Ans. 55 F
272
276. For atmospheric air, given: barometer 30.50 in Hg; temperature, 80 F: relative humidity, 40 %.
A. What is the partial pressure of the water vapor in the air, psia
B. What is the approximate dew point temperature, F.
Ans. 0.20292
Ans. 53.5 F
273
277. For atmospheric air, given: temperature, 78 F; relative humidity, 50 %; barometric pressure, 29.92 in Hg. Calculate, using Steam tables, the mass of water vapor in one
pound of dry air.
Ans. 0.01022
274
278. A compartment contains 3000 ft^3 of air at 75 F, 50 % relative humidity, and at standard atmospheric pressure. Calculate:
A. the mass of water vapor in the compartment, lb
B. the mass of the nitrogen in the compartment, lb
C. the mass of oxygen in the dry air in the compartment, lb
Ans. 2.023
Ans. 167.6
Ans. 50.6
275
279. The observed dry bulb temperature of atmospheric air is 80 F and wet bulb temperature is 72 F. Baometer is standard Find:
A. partial pressure of water vapor, psia
B. pounds of water vapor per pound of dry air, lb/ lb
C. enthalpy of atmospheric air per pound of dry air, Btu/ lb
D. relative humidity in %
E. dew point, F
276
280. A boiler produces 250,000 pounds of steam per hour at 1200 psia and 1050 F from feed water entering the boiler at 1500 psia and 300 F. Fuel oil having a higher heating value of 18,000 Btu/lb is supplied to the burners at the rate of 20,500 lb/br. Furnace volume is 1500 cubic feet. H for steam h = 1528.9 Btu/lb, h for water = 272.39 Btu/lb. Calculate
A. boiler capacity, mB/hr
B. factor of evaporation
C. equivalent evaporation, lb/hr
D. furnace heat release rate, Btu/hr.ft^3
E. boiler efficiency, %
Ans. 314.1
Ans. 1.295
Ans. 323,750
Ans. 246,000
Ans. 85 %
277
281. The following is an ultimate analysis of a typical naval fuel oil, ash and moisture free: Carbon, 0.8663 lb; Hydrogen 0.1127 lb; Oxygen, 0.0019 lb; Nitrogen, 0.0028 lb;Sulfur, 0.0163 lb
Calculate the following for "complete" or "theoretical" combustion with air, in pounds per pound of fuel:
A. oxygen required from air
B. nitrogen required from air
C. air required
D. water formed from combustion
E. carbon dioxide formed
F. total mass of flue gases
Ans. 3.2264, lb/lb fuel
Ans. 10.6805 lb N2/lb fuel
Ans. 13.9069 lb air/lb fuel
Ans. 1.0143 lb/lb fuel
Ans. 3.1767 lb/lb fuel
Ans. 14.9069 lb/lb fuel
278
516. The observed dry bulb temperature of atmospheric air is 80 F and wet bulb temperature is 72 F. Barometer is standard. Find:
A. partial pressure of water vapor, psia
B. pounds of water vapor per pound of dry air, lb/lb
C. enthalpy of atmospheric air per pound of dry air, Btu/lb
D. relative humidity in %
E. dew point, F
Ans. 0.3452 psia
Ans. 0.01496 lb/lb DA
Ans. 35.6 Btu/lb DA
Ans. 68 %
Ans. 68.5 F
279
516. For atmospheric air, given: dry bulb temperature, 84 F; relative humidity, 54 percent. Using psychrometric chart, dotermine:
A. the wet bulb temperature, F
B. the dew point temperature, F
C. the enthalpy, Btu/lb dry air
D. the water vapor, lb/lb dry air
Ans. 71.2
Ans. 66.1
Ans. 35
Ans. 0.0134
280
516. For atmospheric air, given: dry bulb temperature, 85 F; wet bulb temperature,70 F; barometer, standard. The air is cooled at constant total pressure to 50 F. Using psychrometric chart, calculate:
A. the water vapor condensed, grains/lb of dry air
B. the heat rejected, Btu/lb of dry air
Ans. 32
Ans. 13.7
281
516. The data below refer to a two-stage air compressor with interstage cooler. The compressor takes in 100 ft^3/min of atmospheric air.
Entering Entering Entering
L.P. Cylinder Intercooler HP Cylinder
1 2 3
ta, F 90 500 100
tw, F 80 ? ?
p, psia 14. 7 114.7 114.7
Find:
A. the dew point of atmosphere, F
B. the partial pressure of water vapor in atmospheric air, psia
C. the rate of flow of dry air, lb/hr
D. the moisture content at (1), lb vapor/lb DA
E. the moisture content at (3), lb vapor/lb DA
F. the condensate removed by intercooler, lb/hr
Ans. 76.8 F
Ans. 0.4529
Ans. 429.9
Ans. 0.019
Ans. 0.00521
Ans. 6.11
282
516. One hundred pounds of air per minute are to be heated from 60 F dry and 55 F wet bulb temperatures to a final temperature of 110 F. There is no change of total moisture during the process. Determine the heat required for the process, Btu/min
A. by the analytical methods developed
B. by the use of the psychrometric chart. Barometric pressure is 29.92 in Hg.
Ans. 1220 Btu/min
Ans. 1230 Btu/min
283
516. One hundred pounds of air per minute at a temperature of 100 F with a relative humidity of 60 percent are cooled and dehumidified to a final temperature of 50 F. Using the psychrometric chart, determine
A. the heat abstracted by the process, Btu/min
B. the moisture removed, lb/min
Ans. 3150 Btu/min
Ans. 1.743 lb/min
284
516. Ten pounds of air at a dry bulb temperature of 50 F with a specific humidity of 40 grains/lb dry air are mixed with 25 lb of air having a temperature 85 F and a specific humidity of 90 grains/lb dry air. By the methods developed, calculate
A. the specific humidity of the mixture, grains/lb dry air
B. the dry bulb temperature, F
C. the enthalpy of the mixture, Btu/lb dry air
Ans. 75.7
Ans. 75.1
Ans. 29.9
285
516. Using the psychrometric chart, determine
A. the enthalpy, Btu/lb of dry air
B. the specific humdity, grains/lb dry air
Ans. 29.9
Ans. 75.7
286
516. The heat losses from a group of compartments have been determined to be 420,000 Btu/hr. Air is furnished to the compartments at a temperature of 100 F and leaves the spaces with a temperature of 70 F and a relative humidity of 50 percent. Assuming the system to use 100 percent outdoor air at a temperature of 20 F with 100 percent relative humidity, determine:
A. the mass of air which must be circulated, lb/hr
B. the capacity of the preheating coil, Btu/hr
C. the capacity of the reheating coil, Btu/hr
D. the water vapor absorbed from the washer, lb/hr
Ans. 55,260
Ans. 735,000 Btu/hr
Ans. 690,750 Btu/hr
Ans. 308
287
516. For an air-conditioning system such as that described in this article and illustrated in Fig 16-11, the freshened air (state A) has dry and wet bulb temperatures of 83 F and 71 F, respectively, the temperature leaving the cooling coils (state C) is 45 F, the specific humidity after remixing is 51 grains/lb dry air and the temperature and relative humidity leaving the conditioned spaces (state 2) are 80 F and 40 percent, respectively. If the total sensible and latent heat gain from the spaces is 240,000 Btu/hr, calculate:
A. the mass of air that must be circulated, lb/hr
B. the amount of moisture that can be absorbed from the conditioned spaces, lb/hr
C. the fraction of air that bypasses the cooling coil, lb/lb
D. the air that flows through the coil, lb/hr
E. the capacity of the refrigerating plant required for this system, tons
Ans. 27,000
Ans. 38.6
Ans. 0.1372
Ans. 23,300
Ans. 33.6
288
516. In a winter air-conditioning unit consisting of a preheater, humidifier and reheater, the following conditions are maintained:
Point tD φ
1. Air to preheater 51 F 80 %
2. Air to humidifier ? ?
3. Ar to reheater ? 100 %
4. Air from reheater 77 F 50 %
A. What is the wet bulb temperature at point 2, F.
B. What is the dry bulb temperature at point 2, F.
C. If the rate of flow is 350 lb/min of dry air, how many lb/min of water are evaporated in the humidifier?
Ans. 57 F
Ans. 73 F
Ans. 1.3
289
516. Air at 45 F (DB)and 41 F (WB) is heated and humidified to 72 F (DB) and 59 F (WB), To what temperature should the air be heated before humidification?
Ans. 64 F
290
516. Air is to be conditioned from tD= 39 F and φ= 80 percent to tD= 74 F and φ= 70 percent.
A, To what temperature should the air be heated before humidifying, F?
B. How much moisture in grains is added during humidification?
Ans. 102.5 F
Ans. 61 grains/lb DA
291
516, Air is conditioned from tD= 46 F and φ= 60 percent to tD= 70 F and tw= 61 F.
A. To what temperature should the air be heated before humidifying, F?
B. How much moisture in pounds per pound of dry air conditioned must be added in the humidifier?
C. How many BTU must be supplied per pound of dry air conditioned?
Ans. 80 F
Ans. 0.0055 lb/lb DA
Ans. 11.8 Btu/lb DA
292
516. Outside air at tD= 35 F and φ= 50 percent is to be conditioned to tD= 70 F and φ= 60 percent.
A. To what temperature must the air be heated before humidifying, F?
B. How much heat must be supplied per pound of dry air in the heaters, Btu/lb DA?
C. How much heat must be supplied if the air is heated to the final temperature without humidifying, Btu/lb DA?
D. What would be the final relative humidity under the conditions of part C, %?
Ans. 88 F
Ans. 16.4
Ans. 8.4
Ans. 13
293
516. In a summer air-conditioning unit, part of the air is cooled in a refrigerated chamber and then mixed with the remaining untreated air to obtain the desired conditions of temperature and humidity. The following conditions are maintained:
Point tD φ
1. Untreated air 100 F 50 percent
2, Air from cooler ? 100 percent
3. Air from mixing 80 F 80 percent
A. What is the temperature at point 2, F?
B. What percentage of the total air must pass through the cooler?
C. If the total flow is 1000 lb/min of dry air, how much refrigeration in standard tons is required?
Ans. 71 F
Ans. 69 %
Ans. 42.3
294
516. The outside air is at tD= 84 F and φ= 60 percent. A large supply of water is available at 55 F for an air washer. The air through the washer is mixed with outside air at tD= 68 F for compartment cooling.
A. Using the enthalpy method, find the percentage of air bypassed.
B. What is the dew point of the air entering the compartment, F?
Ans. 45 %
Ans, 62 F
295
516. Outside air is conditioned from tD= 92 F and tw= 80 F to tD= 75 F and φ= 80 percent. Heating is accomplished by mixing outdoor air with cooled air.
A. What percentage of air must pass through the cooler?
B. To what temperature must the air passing through the cooler be cooled, F?
Ans. 52 %
Ans. 59 F
296
1. Find the pressure, specific volume, internal energy, enthalpy and entropy of saturated water at 300 F.
Ans. p= 66.98 psia, 0.017448 ft^3/lb, u= 269.52, h= 269.73, s = 0.43720
297
2. Find the temperature, specific volume, internal energy, enthalpy and entropy of saturated steam at a pressure of 1 in Hg absolute.
Ans. t = 79 F, v = 652.7 ft^3/lb, u= 1036.7 Btu/lb, h= 1096.0, s= 2.0384
298
3, Find the temperature, specific volurne, internal energy, enthalpy and entropy of saturated steam at a pressure of 850 psia.
Ans. t= 525.39 F, v= 0.5332 ft^3/lb, u= 1113.9 Btu/lb, h= 1197.7, s= 1.4093
299
4, The pressure and temperature of steam in a line are determined to be 65 psia and 298 F, Since these data are inconclusive, a sample of this steam is passed through a separating calorimeter and 0.5 lb of water is collected in 5 minutes. From orifice data the rate of flow of the dry vapor is found to be 0.4 Ib per minute. Find:
A.the quality
B. the specific volume
C. the entropy
D. the enthalpy
E. the internal energy of the steam in the line
Ans. 80 %
Ans. 5.329 ft^3 /lb
Ans. 1.3973 Btu/lb-R
Ans. 997.2 Btu/lb
Ans. 933.1 Btu/lb
300
5. Steam at 210 psia and 386 F has an enthalpy of 1173 Btu per lb as determined by a throttling calorimeter. Find:
A. the quality
B. the specific volume of this steam
Ans. 96.8 %
Ans. 2.115 ft^3/lb
301
6. At 900 psia and 535 F, find:
A. the superheat
B. the enthalpy
Ans. 2.88 F
Ans. 1199.2 Btu/lb
302
7. For steam at 600 psia and 850 F, find:
A. the superheat
B. the specific volume
C. the internal energy
D. the enthalpy
E. the entropy
Ans. 363.67 F
Ans. 1.2465 ft^3/lb
Ans. 1297.0 Btu/lb
Ans. 1435.4 Btu/lb
Ans. 1.6559 Btu/lb-R
303
8. In a marine-steam propulsion plant, feed water leaves the feed heater and enters the main feed pump at 270 F and a gauge pressure of 35 psi. Find for the water:
A. the specific volume
B. the internal energy
C. the enthalpy
D. the entropy
Ans. 0.017170 ft^3/lb
Ans. 238.82 Btu/lb
Anis. 238.95 Btu/lb
Ans. 0.39597 Btu/lb.R
304
9. Water from the feed pump in the earlier example enters the boiler at 1200 psia and 275 F. Find the enthalpy of the feed water.
Ans. 246.43 Btu/lb
305
10. Steam is admitted to a turbine at 600 psia and 740 F, and exhausts to a condenser at a pressure of 1 psia. Assuming the process to be isentropic, find the drop in enthalpy, Btu/lb.
Ans. 477 Btu/lb
306
11. Steam initially at 10 psia and a quality of 90 percent frops to a pressure of 2.5 psia in a non-flow reversible constant volume process. Show the process on p-v and T-s coordinates and find:
A. the final quality
B. the heat transferred, Btu/lb
Ans. 24.5 %
Ans. (-) 645.5 Btu/lb (abstracted)
307
12. Four pounds of steam initially dry and saturated expand isentropically in a non-flow process from an initially pressure of 275 psia to a final pressure of 125 psia. Show the process on p-v and T-s coordinates and find:
A. the final quality
B.the work done,Btu
Ans. 93.9 %
Ans. 228.4 Btu (by)
308
13. For steam at 705.44 F and 3203.6 psia (critical conditions) find the specific volume, the internal energy, the enthalpy and the entropy for
A. the saturated liquid using Table 1
B. the saturated vapor using Table 2
Ans. 0.05053 ft^3/lb, 872.6 Btu/lb, 902.5 Btu/lb, 1.0580 Btu/lb.R
Ans. 0.05053 ft^3/lb, 872.6 Btu/lb, 902.5 Btu/lb, 1.0580 Btu/b.R
309
14. Find the pressure, specific volume, internal energy, enthalpy and entropy of saturated water at 100 F.
Ans. 0.9503 psia, 0.016130 ft^3/lb, 68.04 Btu/lb, 68.05 Btu/lb, 0.12963 Btu/lb.R
310
15. Find the temperature, specific volume, internal energy, enthalpy and entropy of saturated water at 306 psia.
Ans. 419.24 F , 1.5149 ft^3/lb, 1118.3 Btu/lb, 1204.0 Btu/lb, 1.5098 Btu/lb.R
311
16. For a pressure of 1 1/2 in Hg absolute, determine the pressure in psia, and compute all the Table 2 entries for that pressure.
Ans. 0.737 psia, 91.64 F, vf = 0.016104, vg= 446.5, uf= 59.71, ufg= 981.0, ug= 1040.8, hf= 59.71, hfg= 1041.7,hg= 1101.4, sf= 0.11461, sfg= 1.8893, sg= 2.0039
312
17. Complete the following table where the given data are shown in boldface type.
p(abs) t, F m v u h s
1" Hg 79.0 0.10 587.4 937.7 991.1 1.8437
247.1 400 0.0629 1.7499 1069.9 1150.0 1.4679
350 431.82 0.0256 1.2932 1100.8 1184.5 1.4750
p(abs) t, F m v u h s
1" Hg 79.0 0.10 587.4 937.7 991.1 1.8437
247.1 400 0.0629 1.7499 1069.9 1150.0 1.4679
350 431.82 0.0256 1.2932 1100.8 1184.5 1.4750
313
18. Complete the following table, given the pressures and temperatures shown in the first two columns in boldface.
p(abs) t, F m v u h s
570 850 369.15 1.3151 1297.9 1436.6 1.6622
320 425 1.61 1.4538 1119.4 1205.6 1.5071
p(abs) t, F m v u h s
570 850 369.15 1.3151 1297.9 1436.6 1.6622
320 425 1.61 1.4538 1119.4 1205.6 1.5071
314
19. Find the specific volume, enthalpy and entropy of feed water at 1000 psia and 260 F.
Ans. 0.017029 ft^3/lb, 230.78 Btu/lb, 0.38013 Btu/lb.R
315
20. Identify the conditions of "steam" at the following pressure and temperature:
A. 1150 psia, 300 F
B. 1150 psia, 562 F
C. 1150 psia, 850 F
Ans. compressed liquid
Ans. indeterminate-may be saturated liquid
Ans. superheated
316
21. Steam is supplied to a turbine at 600 psia with 200 F superheated and exhausts to the condenser at 0.7 psia. Assume the process to be isentropic and use the Molier Chart to find
A. the entropy and enthalpy at inlet
B. the enthalpy and moisture content at exhaust
Ans. 1.580 Btu/lb.R, 1342.5 Btu/lb
Ans. 865 Btu/lb, 22.6 % moisture
317
22. Show on T-s and h-s coordinates the following processes for steam, in continuum and in sequence:
A. constant pressure heating from compressed liquid to superheated vapor such as occurs ideally in a boiler
B. isentropic expansion from the superheat region to the wet region such as occurs ideally in a turbine
C. the change of enthalpy
D. the heat added
E. the work done
Ans.
Ans. 1.0025 Btu/lb.R
Ans. 759.6 Btu/lb
Ans. 843.7 Btu/lb
Ans. 84.1 Btu/lb (by)
318
23. Steam initially dry and saturated at saturated at 150 psia expands isentropically in a non-flow process to a final pressure of 15 psia. Show the process on p-v and T-s coordinates and find:
A. the heat transferred
B. the change of internal energy
C. the work done
Ans. 0 Btu/lb
Ans. (-)148.1. Btu/lb
Ans. 148.1 Btu/lb (by)
319
24. Two pounds of water occupy a container in such state that 0.5 Ib is vapor and the remainder is liquid. If the pressure is 30 psia, find:
A. the quality
B. the temperature of the mixture
Ans. 0.25 or 25 %
Ans. 250.34 F
320
25. The design pressure and temperature of steam leaving the boiler are shown in boldface type in the table for
A. a US Navy destroyer escort
B. a 550,000 deadweight tonnage merchant tanker
C. a public utility central station generating plant. Complete the table.
Service p(psia) t, F S.H. u h s
Naval Ship 1200 950 382.6 0.6558 1470.3 1.6091
Tanker 900 950 417.9 0.8896 1480.5 1.6464
Central Station 3500 1050 * 0.2201 1459.6 1.4956
*Not applicable
P.I.P.E. ( Looks Fam )
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