Problem 6.3 - Adiabatic Efficiency of a Power Plant Feedwater Pump

Recall the steam power plant of Example 4.1 in Chapter 4b. Assume that the pump is adiabatic and that the temperature of the water increases by 0.5°C due to friction as it passes through the pump, as in the following figure:

Under these conditions (10 MPa, 40°C) we normally treat liquid water as an incompressible liquid. Determine:the pump adiabatic efficiency (P) defined as the isentropic pump work divided by the actual pump work required to drive the pump. [P = 83%]

Note: In solving this problem we recall the following relations for an incompressible fluid:

where C_H2O = 4.18 kJ/kg.K and specific volume v = 0.001 cu.m/kg.
Thus for the isentropic process:

______________________________________________________________________________________

Engineering Thermodynamics by Israel Urieli is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License