Chapter 7, Problem 7.62P

Given 0.603MW electrical power supplied to a boiler when the temperature of the entering water is 20 C and the exiting temperature is 89 C. The flow of.the pressured water is 2 Kg/s. There is a negligible pressure drop through this boiler and it operates at a constant pressure of 3 bars. The specific heat is c = 4,370 J/(Kg K).  a) Calculate the total rate of entropy production b) Calculate the total rate of exergy destruction (W). The dead state temperature is 293.2 K and pressure is 1 bar. c) Calculate the mass flowrate of fuel (natural gas, CH4) required to heat the water flow to the conditions of the problem if the electrical heating device is replaced with a gas fired boiler. The high heating value (HHV) of the fuel is 50.02 MJ/kg.

A condenser (heat exchanger) brings 1 kg/s water flow at 10 kPa quality 95% to saturated liquid at 10 kPa. The cooling is done by lake water at 20 degree Celsius that returns to the lake at 30 degree Celsius. For an insulated condenser, find the flow rate of cooling water.

Steam to a turbine at a mass flow rate of 1.4 kg/s, 700 kPa pressure and 400 °C enters the temperature. Steam at 100 kPa pressure and 1.4 m3/kg specific volume exits the turbine. Heat transfer from turbine to environment 50 kW, with turbine Since the boundary temperature between the environment is 70 °C, a) Find the power produced by the turbine, entropy produced in the turbine and isentropic efficiency of the turbine. Note: The changes in kinetic and potential energies will be neglected and T (K) = 273 + °C will be taken.