A gas refrigeration system uses helium as the working fluid operates with a pressure ratio of 3.5.

Question:

A gas refrigeration system uses helium as the working fluid operates with a pressure ratio of 3.5. The temperature of the helium is -10oC at the compressor inlet and 50oC at the turbine inlet. Assuming an adiabatic efficiency of 80% for both the compressor and the turbine, determine
(a) The minimum temperature of the cycle,
(b) Mass flow rate for a refrigeration rate of 1 ton and
(c) The COP.