Solved Example for Thermodynamics of Energy Conversion

For the following examples, Appendix B for steam values that I have referred to in these questions was obtained from:

M.D Koretsky, Engineering and Chemical Thermodynamics, Wiley, 2004.

Example 

Consider a power plant operating on a Rankine cycle using steam as the working fluid. The boiler pressure is 2.5MPa and the steam leaving the boiler is superheated to a temperature 126°C above its saturation temperature. The condenser temperature is 50°C and it discharges saturated liquid. The efficiency of the turbine is 0.90 and of the pump 0.80 as compared to reversible and adiabatic machines operating at the same pressure ranges.

a) Sketch the cycle on a T-S diagram.

b) Calculate the thermal efficiency of the cycle.

c) Compare the thermal efficiency of this Rankine cycle with the thermal efficiency of a Carnot cycle receiving heat at the saturation temperature of steam at 2.5MPa and discarding it at 50°C.

Solution

a) 

b) In order to calculate the thermal efficiency, we need to calculate enthalpy values at states 1, 2, 3 and 4.

c)