Chapter 6, Problem 6.17P

Refrigerant 134a at p1 = 30 lbş/in?, T1 = 40°F enters a compressor operating at steady state with a mass flow rate of 250 lb/h and exits as saturated vapor at p2 = 160 lbę/in?. Heat transfer occurs from the compressor to its surroundings, which are at To = 40°F. Changes in kinetic and potential energy can be ignored. The power input to the compressor is 2.5 hp. Determine the heat transfer rate for the compressor, in Btu/hr, and the entropy production rate for the compressor, in Btu/hr-°R.

A divider separates 1 lb mass of carbon monoxide (CO) from a thermal reservoir at 150o F. the carbon monoxide, initially at 60o F  and 150 lbf/in2, expands isothermally to a final pressure of 10 lbf/in2 while receiving heat transfer through the divider from the reservoir. The carbon monoxide can be modeled as an ideal gas. (a) For the carbon monoxide as the system, evaluate the work and heat transfer, each in Btu and the amount of entropy produced, in Btu/oR. (b) Evaluate the entropy production, in Btu/oR, for an enlarged system that includesthe carbon monoxide and the divider, assuming the state of the divider remains unchanged. Compare with the entropy production of part (a) and comment on the difference.

A mass of 3 kg of water contained in a piston–cylinder assembly expand from an initial state where T1 = 551°C, p1 = 700 kPa to a final state where T2 = 224°C, p2 = 300 kPa, with no significant effects of kinetic and potential energy. It is claimed that the water undergoes an adiabatic process between these states, while developing work. Evaluate entropy production in Joules/k.