2. First of all we have to know
the difference between gas
cycles and vapor cycles.
3. Gas cycles :-
In gas cycles the working fluid is gas.
There is no phase change during the whole cycle.
Air is working fluid.
it is the T Vs S graph for gas cycles.
4. Vapor cycles :-
The working fluid is vapor
During the cycle the phase change will occur.
It is liquid at some points in the cycle .
8. From graph
1-2 = isentropic process
2-3 = isobaric process
3-4 = isentropic process
4-1 = isobaric process .
9. Boiler :-
Boiler is used to produce steam .
Heat energy produced by coal is used to produce steam.
Water is allowed to heat until it becomes into vapor state.
Vapor is sent into turbine.
TURBINE :-
Turbine produces the work.
Work produced is used to run the generator.
The enthalpies at the enter and exit of the turbine are different.
Then Vapor is sent into the condenser.
CONDENSER :-
The vapor is condensed to water in the condenser and sent into the
pump.
PUMP :-
Pump send the water again into the Boiler and the cycle repeats again.
10. By considering the devices as steady flow devices and by applying the
energy balance we get
Steam turbine :
W turbine = h1 - h2
Condenser :-
Q rejected = h2 – h3
Pump :-
W pump = h4 – h3
Boiler :-
Q added = h1 – h4
11. Turbine produces the more work if the water is heated to super
heated region.
If the water is heated to super heated then the turbine will produce
the more work .
But there is a problem if water is heated to super heated ie when it
is condensed the vapor is not converted into water completely . It
remains still as a mixture.
It is difficult for the pump to handle both liquid and water which leads
to CAVITATION .
12. Cavitation means sudden formation and collapsing of air bubbles
around the impeller when they moved from low pressure region to high
pressure region.
Cavitation does not show quick effect on the pump but if the cavitation
continues regularly it destroys the pump very badly.
