Real gas model for an electric swashplate refrigeration compressor

Abstract

A real-gas, restricted-flow valve model is compared with an ideal-gas, ideal-valve model for a 10-cylinder swashplate refrigeration compressor. Real gas properties of R134a are evaluated using the NIST standard reference database. A minor-loss discharge-coefficient approach is used to model the refrigerant flow rate through reed valves while the ideal-valve model requires no pressure difference to open the valve. In contrast with the ideal model, the discharge temperature, refrigerant mass flow rate and volumetric efficiency as a function of rotational speed are predicted well by including real-gas properties and flow restriction on the inlet valve. The ideal-gas model significantly overpredicts the discharge temperature and shows no dependence on rpm. Heat transfer to and from the cylinder wall during compression and expansion is found to have only a small effect on predictions of compressor performance. The valve model for the suction side has the largest influence on compressor performance predictions as a function of rpm.