Figure P10.26 shows a two-stage, vapor-compression refrigeration system with two evaporators and a direct-contact heat exchanger. Saturated vapor ammonia from evaporator 1 enters compressor 1 at 18 lbf/in.2 and exits at 70 lbf/in.2 Evaporator 2 operates at 70 lbf/in.2, with saturated vapor exiting at state 8. The condenser pressure is 200 lbf/in.2, and saturated liquid refrigerant exits the condenser. Each compressor stage has an isentropic efficiency of 80%. The refrigeration capacity of each evaporator is shown on the figure. Sketch the T–s diagram of the cycle and determine
a. the temperatures, in °F, of the refrigerant in each evaporator. b. the power input to each compressor stage, in horsepower.
c. the overall coefficient of performance.
