# Thermodynamics and Thermal Efficiency

(a) the thermal efficiency.

(b) the back work ratio.

(c) the net work of the cycle per unit mass of water flowing, in kJ/kg.

(d) the heat transfer from the working fluid passing through the condenser, in kJ per kg of steam flowing.

(e) Compare the results of parts (a)–(d) with those of Problem 8.6, respectively, and comment.

8.8 Plot each of the quantities calculated in Problem 8.6 versus turbine inlet temperature ranging from the saturation temperature at 18 MPa to 560C. Discuss.

8.9 A power plant based on the Rankine cycle is under

development to provide a net power output of 10 MW. Solar

collectors are to be used to generate Refrigerant 22 vapor at 1.6 MPa, 50C, for expansion through the turbine. Cooling

water is available at 20C. Specify the preliminary design of the cycle and estimate the thermal efficiency and the refrigerant and cooling water flow rates, in kg/h.

8.10 Refrigerant 134a is the working fluid in a solar power plant operating on a Rankine cycle. Saturated vapor at 60C enters the turbine, and the condenser operates at a pressure of 6 bar. The rate of energy input to the collectors from solar radiation is 0.4 kW per m2 of collector surface area. Determine the minimum possible solar collector surface area, in m2, per kW of

power developed by the plant.

8.11 The cycle of Problem 8.3 is modified to include the effects of irreversibilities in the adiabatic expansion and compression processes. If the states at the turbine and pump inlets

remain unchanged, repeat parts (a)–(d) of Problem...

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