A gas refrigeration cycle with a pressure ratio of 3 uses helium as the working fluid. The

Question:

A gas refrigeration cycle with a pressure ratio of 3 uses helium as the working fluid. The temperature of the helium is -10°C at the compressor inlet and 50°C at the turbine inlet. Assuming adiabatic efficiencies of 80 percent for both the turbine and the compressor, determine
(a) The minimum temperature in the cycle,
(b) The coefficient of performance, and
(c) The mass flow rate of the helium for a refrigeration rate of 18 kW.