Development of High-Efficiency Technology of Two-Stage Rotary Expander for CO2 Refrigerant

In order to improve the coefficient of performance (COP) of a heat pump cycle by using carbon dioxide (CO2), an expander that recovers rotation power from the large pressure difference in the cycle to use the power to partially drive the cycle was developed. In the cycle a two stage rotary expander was adopted because the suction control mechanism is not necessary in it. In the development process of pursuing higher efficiency, a performance analysis simulation model was developed by combining the dynamic mechanical analysis and the refrigerant pressure analysis in the expander by taking refrigerant leakage into consideration. After examining the impact of each design parameter on the performance by using the simulation, an optimized design has been produced and the expander efficiency of 60% along with the improvement of cycle COP by 6% have been achieved in a short term.