A test system for measuring valve displacement and p-V diagrams was established and the experiment on the dynamics of the discharge valves was conducted to understand the influences of the large density and high pressure difference across the reciprocating compressor valves on the valve dynamics in a transcritical CO

2

refrigeration cycle. The results show that main factors affecting the valve movement include pressure ratio

valve lift

valve thickness

spring stiffness

and compressor speed. Moreover

a lower pressure ratio and smaller valve lift would enhance the valve reliability. A higher rotation speed would raise the volumetric efficiency of the compressor while it would increase the valve impact velocity. It appears that the compressor efficiency could be improved by reducing the energy loss in the suction and discharge process

especially in the beginning period of the discharge process.