A comprehensive physics-based model for a semi-hermetic CO2 reciprocating compressor is presented. The model is composed of two major sub modules

the thermal module and the mechanical module. The thermal module is used to simulate the vapor compression process inside the cylinder

while the mechanical module is to simulate the frictional loss happened in the bearing connected to the cylinder. Extensive experimental validation of the compressor model were carried out for a CO2 prototype compressor under different operating conditions. The maximum deviations of mass flow rate and power consumption are within 3% and 8%

respectively. Furthermore

parametric study was conducted to investigate the compressor performance as a function of the stroke-to-bore ratio and the gap between cylinder and piston under different operating conditions. The results indicated that there is an optimal stroke-to-bore ratio under different operating conditions. Both volumetric efficiency and isentropic efficiency fall with the increasing compressor speed. There are optimal diameters for suction and discharge valves. On the volumetric efficiency

the gap between suction valve and valve seat has heavier impact than the gap between discharge valve and valve seat

while the gap between piston and cylinder has greater impact than the gap between cylinder and cylinder ring. The analysis would help further improvement on the compressor design.