Takeshi Ogata

Development of the High-Efficiency Technology of a CO2 Two-Stage Rotary Expander

To improve the coefficient of performance of a heat pump cycle by using carbon dioxide, an expander was developed that recovers rotation power from the large pressure difference in the cycle and uses the power to partially drive the cycle. In the cycle, a two-stage rotary expander was adopted, because the suction control mechanism is not necessary in it. A performance analysis model was developed by combining the dynamic mechanical analysis and the refrigerant pressure analysis in the expander and taking refrigerant leakage into consideration. After examining the impact of each design parameter on the performance of the two-stage rotary expander, an optimized design was determined. With this design, an expander efficiency of 54% could be achieved in a short period of time.