Practice Problems Exam 3

Practice problems Chapter 8 (Vapor Power Systems) 1) Water is the working fluid in an ideal Rankine cycle. Superheated vapor enters the turbine at 8MPa, 480oC. The condenser pressure is 8kPa. The mass flow rate of steam leaving the boiler is 5 kg/s. Determine: A) The rate of heat transfer to the working fluid passing through the steam generator in kW, B) the thermal efficiency C) Net power output in MW, and D) The mass flow rate of condenser cooling water, if the cooling water enters the condenser at 15oC and exits at 35oC with negligible pressure change. 2) Modify the cycle in Problem 1 by considering turbine efficiency of 85% and pump efficiency of 80%. Determine the thermal efficiency of the modified cycle. 3) Modify the ideal Rankine cycle of Problem 1 to include reheat at 0.7 MPa. The steam is reheated to 440oC before entering the second turbine. Determine the thermal efficiency of the modified cycle. 4) Modify the reheat cycle of Problem 3 to include an open feedwater heater at 0.3 MPa. Saturated liquid exits the feedwater heater at 0.3 MPa. Determine the thermal efficiency of the modified cycle and the net power output.

Chapter 10 (Vapor Compression Refrigeration and Heat Pumps)