Description: Slide 1: VAPOR AND COMBINED POWER CYCLES
Slide 2: In previous Chapter, we discussed gas power cycles for which the
Slide 3: THE CARNOT VAPOR CYCLE
Slide 4: Several impracticalities (unrealistic) are associated with this cycle:

Slide 5: The isentropic expansion process (process 2-3) can be approximated
Slide 6: The isentropic compression process (process 4-1) involves the
Slide 7: Some of these problems could be
Slide 8: RANKINE CYCLE
Slide 9: RANKINE CYCLE: THE IDEAL CYCLE FOR VAPOR POWER CYCLES
Slide 10: Rankine cycle is the ideal cycle for vapor
Slide 11: Water enters the pump at state 1 as saturated
Slide 12: Water enters the boiler as a compressed
Slide 13: The superheated vapor at state 3 enters the
Slide 14: In areas where water is precious, the power plants are cooled by air
Slide 15: Energy Analysis of the Ideal Rankine Cycle
Slide 16: The boiler and the condenser do not involve any work, and the pump
Slide 17: The conversion efficiency of power plants in the United States is often
Slide 18: DEVIATION OF ACTUAL VAPOR POWER CYCLES FROM IDEALIZED ONES
Slide 19: Fluid friction
Slide 20: Heat loss
Slide 21: Of particular importance are the irreversibilities
Slide 22: where states 2a and 4a are the actual
Slide 23: HOW CAN WE INCREASE THE EFFICIENCY OF THE RANKINE CYCLE?
Slide 24: Lowering the Condenser Pressure (Lowers Tlow,avg)
Slide 25: For comparison purposes, the turbine inlet
Slide 26: Superheating the Steam to High Temperatures (Increases Thigh,avg)
Slide 27: Thus both the net work and heat input
Slide 28: The temperature to which steam can be
Slide 29: Increasing the Boiler Pressure (Increases Thigh,avg)
Slide 30: The effect of increasing the boiler pressure
Slide 31: Operating pressures of boilers have
Slide 32: THE IDEAL REHEAT RANKINE CYCLE
Slide 33: Two possibilities come to mind:

Slide 34: The T-s diagram of the ideal reheat Rankine cycle and the schematic
Slide 35: The ideal reheat Rankine cycle differs from the simple ideal Rankine cycle in that
Slide 36: Thus the total heat input and the total turbine work output for a
Slide 37: The average temperature during the reheat
Slide 38: The reheat cycle was introduced in the mid-1920s, but it was
Slide 39: THE IDEAL REGENERATIVE RANKINE CYCLE
Slide 40: To overcome this shortcoming, we look
Slide 41: A practical regeneration process in steam power plants is accomplished by
Slide 42: A feedwater heater is basically a heat exchanger where heat is
Slide 43: Open Feedwater Heaters
Slide 44: The schematic of a steam power plant with one open feedwater
Slide 45: In an ideal regenerative Rankine cycle,
Slide 46: The condensed water, which is also called
Slide 47: In the analysis of steam power plants, it
Slide 48: If the mass flow rate through the boiler
Slide 49: In light of Fig. 10–15, the heat and work
Slide 50: The thermal efficiency of the Rankine cycle increases as a result of
Slide 51: Closed Feedwater Heaters
Slide 52: The two streams now can be at different pressures, since they do not
Slide 53: In an ideal closed feedwater heater, the feedwater is heated to the
Slide 54: The open and closed feedwater heaters can be compared as follows:

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