Reference no: EM13626394

a) Consider the steady operation of a refrigeration "package" for a shipping container (on a train, truck or ship). The package is self contained and is fueled by a tank of propane. The unit is composed of an internalcombustion engine that drives an R134a refrigeration cycle. The engine produces 10 kW of shaft power with a thermal efficiency of 20% when operating with a maximum temperature of 2000 oF and cooled by the +59 oF atmosphere. The refrigeration cycle has a COP of 2.5 when cooling the contents of the shipping container at -20 oF and rejecting waste heat into the +59 oF atmosphere. Determine the cooling capacity of the device and the actual COP of the combined-cycle package = useful effect/expensive input. Also determine the maximum reversible COP and the theoretical minimum fuel energy input required to provide the same cooling effect as the actual package. (Notice that the 10 kW of power produced is entirely absorbed to drive the refrigerator so the external work is zero. The thermal efficiency definition is based on the energy available from the propane fuel.)

b) Consider the steady operation of a different self-contained refrigeration "package" for a shipping container. The device is thermally activated by heat transfer input from a steady 2000 oF external source. The external thermal source is due to complete external combustion of the propane fuel. Assume all of the fuel energy is input into the device. The device absorbs 5 kJ/s of heat transfer from a -20 oF shipping container and rejects 9 kJ/s of waste heat to the +59 oF atmosphere. Determine the actual COP of this "thermally-activated refrigeration package" cycle = useful energy effect/expensive energy input. Also determine the maximum reversible COP and the theoretical minimum fuel energy input required to provide a 5 kJ/s cooling effect. Notice external work is zero; for a reversible cycle, S(Q/T)REV = 0.