Compare the thermal efficiency of the cycle when it is operated such that the saturated liquid enters the pump against that when the sub-cooled liquid enters the pump.
Explanation of Solution
Given:
Pressure of steam at the boiler
Pressure of steam at the condenser
Temperature of steam at the turbine inlet
Temperature of sub-cooled liquid
Calculation:
Draw the
The pressures are constant for the process 2 to 3 and process 4 to 1.
The entropies are constant for the process 1 to 2 and process 3 to 4.
The thermal efficiency of the cycle when it is operated such that when the saturated liquid enters the pump:
Refer Table A-5, “Saturated water-Pressure table”, obtain the specific enthalpy and specific volume at state 1 corresponding to the pressure of
Calculate the work done by the pump during process 1-2
Calculate the specific enthalpy at state 2
Refer Table A-6, “Superheated water”, obtain the specific enthalpy and temperature at state 3 corresponding to the pressure of
Refer Table A-5, “Saturated water-Pressure table”, obtain the following properties corresponding to the pressure of
Calculate the quality of steam at state 4
Calculate the specific enthalpy at state 4
Calculate the thermal efficiency of the cycle
The thermal efficiency of the cycle when it is operated such that when the sub-cooled liquid enters the pump:
Refer Table A-5, “Saturated water-Pressure table”, obtain the saturation temperature corresponding to the pressure of
Calculate the temperature at state 1
Refer Table A-4, “Saturated water-Temperature table”, obtain the specific enthalpy and specific volume at state 1 corresponding to the temperature of
Calculate the work done by the pump during process 1-2
Calculate the enthalpy at state 2
Calculate the thermal efficiency of the cycle
By comparing the thermal efficiencies of the cycle, it is found that the thermal efficiency slightly reduces because of the sub-cooling at the inlet of the pump.
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Chapter 9 Solutions
Fundamentals of Thermal-Fluid Sciences
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