Performance Analysis of Heat Pump Cycle with an Expander

A simulation investigation have been carried out to research the relationships between rejection pressure and related operating parameters and the performance of a heat pump cycle with an expander (HPCE) respectively using CO2 and R134a as refrigerant. With the increase of exhaust pressure, the CO2 cycle has an optimum rejection pressure that is 8.667MPa, and the maximal COP is 4.189, in addition, R134a cycle is a reducing trend. When the Condensing temperature of compressor is gradually increasing, the performances of CO2 cycles gradually decline, but the R134a cycle just has small changes. With the increasing of evaporating temperature, the performances of all cycles are an increasing trend.