In a steam power plant, some steam from the turbine is bled off (stream 1) and used in a mixing chamber to heat sub-cooled water (stream 2) before it enters the boiler. Stream 1 is at a pressure of 100 lbf/in2 and a quality of 98% (state 1) while stream 2 is at a pressure of 100 lbf/in2 and a temperature of 80°F. The mixed stream leaves the mixing chamber at a pressure of 95 lbf/in2 and at a temperature of 290°F (state 3) with a mass flow rate of 25,000 lbm/hr. The flow through the mixing chamber is at steady state. The mixing chamber can be assumed to be adiabatic, and the changes in kinetic and potential energy can be neglected.
(a) Calculate the mass flow rate (lbm/hr) for stream 1 and stream 2.
(b) What is the rate of entropy generation (Btu/hr-°R) for the mixing chamber?
(c) Show all states on T-s diagram. You must label states, show temperature and specific entropy values, and indicate appropriate lines of constant pressure.