Abstract: Due to the advantage of global environmental protection, carbon dioxide, the natural refrigerant, has been attracting increasing attention over the last ten years. The low performance efficiency of the CO2 transcritical cycle is the main problem for the practical application. In order to reduce the irreversible loss caused by the throttling process from the supercritical region to the sub-critical and improve the coefficient of performance of CO2 cycle, an expander is adopted to replace the throttle valve and recover the expansion power. A hermetic swing expander in transcritical carbon dioxide cycle water source heat pump is developed. The structure of swing expander and stress on the swing piston are analyzed. The experiment on CO2 transcritical cycle water source heat pump is conducted. The results indicate that swing expander is suitable for the operation under high pressure. Under the test condition, the efficiency of the swing expander can reach 44%.

Key words: Carbon dioxide transcritical cycle, Swing expander, Water source-heat pump