Best quality coal
Anthracite
Most used coal
Bituminous
Components of rankine cycle
Pump - turbine
Condeser - boiler
Processes in rankine cycle
2 constant pressure & 2 isentropic
Efficiency of rankine cycle
Wnet/Qs
Heat rate
Qin/Wnet
3600/efficiency
Unit kj/kwhr
Steam rate
Amount of steam consumed in kg/hr to produce 1 kW power output.
SR = 3600/Wnet
Work ratio
Wnet/Wturbine
Back work ratio
1- work ratio
Pump work/turbine work
What happens if dryness fraction is low
Water droplets hit turbine blades
Blade erosion
Loss of efficiency
Mechanical damage
Methods to improve efficiency of rankine cycle
1.Decrease condenser pressure
2.Increase boiler pressure
3.Superheating
The only objective of reheating in rankine cycle
To increase dryness fraction at exit of turbine
Effects of reheating
Dryness fraction increases
Work turbine increases
Wnet increases
Qsupplied increases
Optimum reheat pressure
0.2 to 0.25 boiler pressure
Size of the boiler decrease in reheat cycle why
Since network is increasing steam right decreases
How efficiency is increased in regeneration
By decreasing heat supplied with the help of feed water heater
Regeneration
It is the only method by which efficiency can be increased and multiple reservation in Irreversible cycle can lead to efficiency close up to carnot cycle
What is bleeding
Steam extracted from turbine during expansion
How Regeneration is done
Stream extracted from turbine during expansion and the subsequently used for heating water
Why open type feed water is called deaertor
Because it to remove non condensable gases
Effects of regeneration
Efficiency will increase
heat supplied decreases
meann temperates of heat addition increases
Power load factor
Annual production of energy/capacity of plant×operational hour in year
Efficiency can be increased by decreasing condenser pressure but the disadvantage is
Dryness fraction at the exit of turbine is decresed
Efficiency is increased by increasing boiler pressure but the disadvantages is
Dryness fraction decreases
