A central refrigeration unit for ordinary food storage is being designed to provide 36000 Btu/h of cooling capacity. The unit will operate on a standard vapor-compression refrigeration cycle with throttling expansion. Freon 12 will be used as the working fluid. The evaporator temperature will be held at 20 ⁰ F, the condenser will operate at 100 0F. 

a) Determine the flow rate of the working fluid, the compressor horsepower, and the total heat load of the condenser. Assume reversible compression. 

b) What will be the flow rate if the throttling valve is exchanged with an is entropic expansion engine?