RACT Unit 22

Question 1

The condenser is a heat exchange device that _______ heat from the system

Answer 1

rejects

Question 2

What are the 3 main functions of a compressor in order of occurrence?

Answer 2

1. De-superheating the vapour
2. Condensing vapours to liquid
3. sub cooling the liquid

Question 3

What main function has the greatest amount of heat absorbed in the system?

Answer 3

When the refrigeration is changing state (vapour to liquid)

Question 4

The condenser operates at _______ pressures and temperatures than the evaporator and is often located _______

Answer 4

higher, outside

Question 5

Water cooled condensers can operate at much _____ condensing temps

Answer 5

lower

Question 6

Because water has a _____ specific heat and density than air, water cooled condensers are more _______ than air cooled

Answer 6

higher, efficient

Question 7

The condenser also rejects heat picked up in the ______ line, _______ and heat of ______ compression

Answer 7

suction line, compressor, and heat of compression

Question 8

Three types of water cooled condensers are:

1. Tube within a _____ condenser (double tube)
2. Shell and ______ condenser
3. Shell and ____ condenser

Answer 8

1. tube within a tube condenser (double tube)
2. shell and coil condenser
3. shell and tube condenser

Question 9

Tube-within-a-tube Condensers:

1. Two styles: the ____ type and the _______ type with flanged ends
2. Heat exchange takes place between the fluids in the ______ and _______ tube
3. Refrigerant flows in the ______ tube
4. Refrigerant and water flow in _______ directions to maximize the _______ rate

Answer 9

1. coil type and cleanable type
2. Inner and outer
3. outer tube
4. opposite, transfer rate

Question 10

A tube within a tube condenser is constructed by sliding one tube through another tube. The tubes are _______ in such a manner that the inside tube is ________ from the outside tube

Answer 10

sealed, separated

Question 11

Mineral deposits:

1. Heat from the ________ gas causes minerals to come out of solution

1A) Form scale that adheres to the _____
1A) i) Scale acts as an _______, reducing heat transfer

1B) Water is chemically treated to reduce ______ formation on the interior pipe surfaces

1C) Dirty condensers lead to ____ ______ pressures

1D) Tube within a tube condenser can not be cleaned mechanically with ______

Answer 11

1. discharge gas

1A) pipes
1A) i) insulator

1B) scale

1C) high head pressures

1D) brushes

Question 12

Scale deposits are normally found on the inner ______ tube

Answer 12

water

Question 13

Cleanable tube-within-a-tube condensers:

1. Have end _______, which are removed to access the _______ circuit
2. The _________ circuit remains sealed while the ________ circuit is open
3. Straight tubes are more expensive, but more easily ________
4. ________ pump and chemicals are used to ______ the water tube circuit

Answer 13

1. flanges, water circuit
2. refrigerant , water
3. serviced
4. circulator pump, descale

Question 14

Cleanable Tube-within-a-tube Condensers: Cleaning brush

Parts;

1. Rotating _____
2. water _____
3. flexible _____
4. Nylon _______

Answer 14

1. rotating brush
2. water flush
3. flexible shaft
4. nylon casing

Question 15

Shell and Coil Condensers:

1. Coil of tubing enclosed in a ________ shell
2. Water flows through the _______
3. Refrigerant from the comp is discharged into the ______

3A) Shell also acts as a ________ storage tank

4. When ref comes in contact with the cool coil, it _________ and falls to the bottom
5. This condenser must be cleaned __________

Answer 15

1. welded
2. coil
3. shell

3A) receiver

4. condenses
5. chemically

Question 16

Shell and coil condensers:

The hot refrigerant gas is piped into the _______ and the water is contained inside the _______

Answer 16

shell , tubes

Question 17

Shell and Tube Condensers:

1. Most _________ type or condenser
2. normally used in _______ installations
3. Can be cleaned ____________ with _______

3A) Comp discharge gas is piped into the ______
3A) i) Water flows through the _____ in the cond.
3A) ii) The ends of the shell are removed for _______
3A) iii) The shell acts as a _______ storage tank

Answer 17

1. Expensive
2. Larger
3. Mechanically, brushes

3A) piped
3A) i) tubes
3A) ii) cleaning
3A) iii) Receiver

Question 18

Four-Pass Shell-and-tube Condenser:

1. Water can be circulated back and forth through the condenser by using the ____ _____ to give the water proper direction
2. The number of _____ passes will vary with the ____ plate design

Answer 18

1. end caps

2. water, end plate design

Question 19

Wastewater Systems:

1. Water used once and then ______ down the drain

1A) Economical of water is _____ or system is _____

1B) Drawback: Water ______ can vary greatly

1C) Amount of water needed depends on the temp difference between the water ____ and _____ of the __________

Answer 19

1. wasted

1A) free, small

1B) temperature

1C) in, out, condenser

Question 20

Wastewater systems: Plentiful water;

Waste water systems are used when water is _______ and at a low _____ such as from a well or lake

Answer 20

plentiful, low cost

Question 21

Refrigerant-to-water Temperature Relationship for Wastewater Systems:

1. Water flow can be varied using a _____- ________ valve with a ________ tap
2. Constant _______ pressure maintained by letting more or less water into the condenser as the head pressure changes
3. Water ____ temperatures often vary with the ______

3A) Faster inlet when water is ______
3B) Slower inlet when water is _______

Answer 21

1. water-regulating valve, pressure tap
2. head
3. inlet , season

3A) warmer

3B) colder

Question 22

Re-circulating water systems:

1. The water flowing through condenser pumped to a _______ location, ______ , and _______

1A) Design water temp is ___F

1B) A water flow rate of ___ gpm per ton of refrigeration is required to absorb heat

1C) There is a ___F split across the ______ circuit

Answer 22

1. remote location, cooled, and reused

1A) 85F

1B) 3.0gpm

1C) 10F, water circuit

Question 23

Recirculating Water Systems Described:

1. The water cooled condenser absorbs _____ from the refrigerant, ______ the water to a cooling tower at a ______ location
2. Condenser is located _____ to the compressor and tower is on the ____ outside the structure

Answer 23

1. heat, pumps, remote

2. close, roof

Question 24

Cooling Towers:

1. Device that passes outside ____ over ______ to remove system _____
2. Capacity limited by the amount of ________ that occurs at any given time

2A) Towers can cool the water to a temp within ___F of the ____ - _____ temp of the air surrounding the tower

3. Types; (3)

Answer 24

1. air, water, heat
2. evaporation

2A) 7F, wet-bulb

3. Natural Air, forced draft, evaporative

Question 25

Forced-Draft Cooling Tower: 1. The relationship of a forced-draft cooling tower to the _______ air. 1. A) Cooling tower performance depends on the ___-____ temp of the air 1B) This relates to the ______ and the ability of the air to absorb _______

Answer 25

1. ambient 1A) wet-bulb 1B) humidity , moisture

Question 26

Natural-Draft Towers: 1. Often made of ___wood, fibreglass or ________ sheet metal 2. No ______ to move air through 2A) natural ______ move air through the tower 3. Water enters the tower from the ____ and is cooled as it falls to the ______ 3A) Some _________ in the process, helping to cool the remaining ______ in the tower 4. Additional water added through a ______ valve

Answer 26

1. redwood, fibreglass , or galvanized sheet metal 2. No blowers 2A) natural breezes 3. top, bottom 3A) evaporates, remaining water 4. float valve

Question 27

Forced - or Induced-Draft Towers: 1. Uses ____ or _______ to move air through 1A) As ______ falls through the tower, air is moved across to air in _______ 2. Can be located almost ________ 3. The fan cycled ___ and ____ to maintain the desired ________ temperature 3A) Forced draft: air is _____ through tower 3B) Induced draft: air is _______ through the tower

Answer 27

1. fan or blower 1A) water, aid in cooling 2. anywhere 3. on and off, water 3A) pushed through 3B) pulled through

Question 28

Evaporative Condensers: 1. Located ______ cooling tower 2. Uses the ______water over and over by means of a ______ located at the tower 3. _______ system replaces evaporated water 4. Both ___ and ______ used to desuperheat, condense, and subcool refrigerant 5. Water allowed to escape on a regular bases to prevent ______ ________ 5A) Water escaping is called ____down

Answer 28

1. Inside 2. same, pump 3. Makeup 4. air and water 5. prevent mineral deposits 5A) blowdown

Question 29

Air-Cooled Condensers: 1. ____ absorbs heat rejected by the system in locations where water is difficult to use 2. Horizontal, ______ or _____ intake and top discharge 3. Hot gas enters the condenser from the ____ 4. For standard efficiency systems, the refrigerant will condense at a temp about ___F higher than the outside _______ temperature

Answer 29

1. Air 2. horizontal, vertical, or side intake and top discharge 3. from the top 4. 30F higher then outside ambient air temp

Question 30

Air-Cooled Condensers: Function of Fins; 1. Fins are designed to give the coil more _______ ____

Answer 30

1. surface area

Question 31

High-Efficiency Condensers: 1. Have _______ surface areas than standard condensers 1A) Allow systems to operate at ______ pressure 1B) allow systems to operate more _________ 1C) Can operate with ______ pressure as low as ___F higher than the outside ambient air temp

Answer 31

1. large 1A) lower pressure 1B) more efficiently 1C) head pressure as low as 10F

Question 32

The Condenser and Low Ambient Conditions: 1. Condensing temperatures drop when the outside ambient temperature ____ 1A) Reduces the ________ pressure on the ____ pressure side of the system 1B) A _______ evap coil may result

Answer 32

1. drops 1A) reduces operating pressure on the high-pressure side 1B) starved evaporator coil

Question 33

Head Pressure Controls: Practical Methods; Methods to maintain correct head pressure: 1. Fan-_____ controls 2. Variable-_______ drive (VFD) condenser fan motor controls 3. Da_____ 4. _______ flooding 5. Condenser _______

Answer 33

1. Fan-cycling control 2. Variable-frequency drive 3. dampers 4. condenser flooding 5. condenser splitting

Question 34

Head Pressure Controls: Fan Cycling Devices; 1. Used on _____- cooled condensers 2. As head pressure drops, fan cycles ____ 3. As head pressure rises, fan cycles _____ 4. Can be added without much ______ 5. Causes _____ pressure to swing up and down 6. Some condensers may have _____ then one fan 6A) May remain on at all times or _____ on/off 6B) Head and ______ pressures will decrease

Answer 34

1. air cooled condensers 2. cycles off 3. cycles on 4. without much expense 5. head pressure to swing up and down 6. more than one fan 6A) cycle on/off 6B) Receiver

Question 35

Head Pressure Controls: VFD Condenser Fan Motors; 1. Vary speed gradually according to _____ pressure or outside ambient temperature _____ 2. Motor speed changes as the incoming ______ frequency changes 3. Keeps a more _______ head pressure 3A) prevents erratic head press changes seen in ____ motor _____ cycling

Answer 35

1. head pressure, ambient temp changes 2. voltage 3. consistent 3A) seen in fan motor cycling

Question 36

Head Pressure Controls: Air Shutters or Dampers: 1. Located at the _____ or the _______ 2. Operated by pressure-controlled ______ 3. Provide ____ head pressure control

Answer 36

1. Inlet or outlet 2. piston 3. even

Question 37

Head Pressure Controls: Air Shutters or Dampers: With a single fan: 1. Shutter installed over the ____ or over the _____ to the fan With Multiple fans: 2. Shutter-covered fan operated ___ the _____ 2A) Others _____ by pressure or temp

Answer 37

1. over the inlet or outlet 2. All the time 2A) cycled by press or temp

Question 38

Head Pressure Controls: Condenser Flooding; 1. Causes head pressure to ____ 2. Accomplished by having enough refrigerant in the system to flood the condenser in the ____ and ____ weather 2A) Requires a _____ ref charge and an _______ liquid receiver 2B) Also required a valve ________ that allows the refrigerant liquid to fill the condenser during mild and cold weather

Answer 38

1. rise 2. mild and cold 2A) large refrigerant charge and oversized liquid receiver 2B) valve arrangement that allows ref to fill cond during mild and cold weather

Question 39

Head Pressure Controls: Condenser Splitting; 1. Reduces extra refrigerant charge needed for ________ flooding 2. ____ the condenser in two separate identical condenser ______ 2A) ______/______ condenser, _______ condenser 3. _______ valve control energized/de-energized by controller sensing outside _____ temperature, an outdoor thermostats or a high-side pressure control

Answer 39

1. condenser 2. Splits, circuits 2A) Summer/Winter condenser, Summer Condenser 3. Solenoid valve control, sensing outdoor ambient temp

Question 40

Using the Condenser Superheat: 1. ___-cooled condensers have ____ discharge temperatures 2. Can be captured and redistributed as _____ for the structure in the ______ or to heat ______

Answer 40

1. air cooled condensers have high discharge temps | 2. captured and redistributed as heat for the structure in water or to heat water

Question 41

Floating Head Pressures: 1. Term used for attaining the _______ possible ________ temperature 2. Allows the head pressure to follow the ______ temp without using head pressure _______ 2A) TXV and some newer expansion devices can operate with pressure differences as low as ____psig 2B) Systems become ______ efficient since they operate at ______ pressure

Answer 41

1. lowest possible condensing temperature 2. follow the ambient temp without using head pressure controls 2A) as low as 30 psig 2B) more efficient since they operate at lower pressures