What is Reheat Rankin Cycle?




Reheat Rankin Cycle:

The drawback of having high pressure in the boiler is the increase of water content at the blades steam turbine. To avoid this problem, reheat Rankin cycle is used.
The diagram for the Reheat Rankin cycle is shown.




We can enhance the thermal efficiency of the steam turbine power plant by reheating the steam coming from high pressure turbine, approximately to same temperature as the inlet of the first turbine and then passing it from an another turbine operating at low pressure, called low pressure turbine. By this arrangement, the dryness fraction at the exit of low pressure turbine is increase which is desirable to increase the thermal efficiency of the Plant.

The various processes in Reheat Rankin Cycle are:

1-2: Isentropic Expansion of superheated steam in the high pressure turbine.

2-3: Constant pressure reheating in the Re-heater.

3-4: Isentropic expansion in low pressure turbine.

4-5: Heat rejection in the condenser at constant temperature and pressure.

5-6: Isentropic pressure rise in the Pump.

6-7: Heating of sub-cooled liquid

7-1: Constant Pressure Reheating in the Boiler.

Heat supplied to the Boiler = h1 - h6 = Q1

Heat rejected to the condenser = h4 - h5 = Q2

Total Work output = Wt1 + Wt2 = Work done in low pressure turbine + Work done in high pressure turbine = (h1 - h2) + (h3 - h4)

Total Heat supplied = heat supplied in the Boiler + Heat supplied in the Re-heater = (h1 -h6) + (h3 - h2)

Thermal efficiency = Net work output/ Total heat supplied = {(h1 - h2) + (h3 - h4) – (h6 - h5)}/ {(h1 -h2) + (h3 - h2)}

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1 comment:

  1. This is very Informative kind of Blog covering the Basics of a Power Plant Technology.

    ReplyDelete