A walk-in cooler using a vapor compression refrigeration cycle is configured as shown below. The cycle uses CFC22 or R22 as the refrigerant. Assume frictionless flow through all piping and heat exchangers (e.g. neglect pressure drops except through the expansion valve). Assume saturated liquid leaves the condenser and saturated vapor leaves the evaporator. A heat exchanger is used to transfer thermal energy between the hot liquid leaving the condenser and the cold vapor leaving the evaporator. Assume this heat exchanger has perfect external insulation so the only energy transfer is between the two fluids. The main purpose of this heat exchanger is to prevent liquid from entering the compressor and damaging it. Known data are: T1 =30 °C, T2 =10 °C and T4 = -10 °C.
a) Find the coefficient of performance and the temperature T6 after the compressor for isentropic compressor efficiency 0.75.
b) For the above range of compressor efficiencies, determine how much electrical power is needed to achieve a refrigeration capacity of 1 ton refrigeration.