Simulation of single and two-phase refrigerant compression in rotary compressors

Abstract

Liquid slugging, which often happens during startup and defrosting processes of the air conditioning, is a great threat to the reliability of rotary compressors, because of its high pressure in the compression chamber. In this paper, a coupled mathematical model that can predict the compression process of refrigerants in three different states in the compressor cylinder is proposed. The refrigerant phase change, heat exchange between refrigerant and wall, leakage through leak passage and refrigerant kinetic energy change rate are considered in the model. The coupled solution method and its Fortran calculation program are carried out. This mathematical model is experimentally verified by using R290 as refrigerant. The results show that the simulation results of pressure variation in the compressor cylinder during the refrigerant two-phase compression and discharge processes are consistent with the experimental values. The liquid slugging happens with the maximum pressure of 2400 kPa in the cylinder under low suction gas mass fraction. The R290 is more prone to condense during in-cylinder compression than that of R22 and R410A under low wall temperature condition. The larger the volume change rate of the compression chamber, the higher compressor rotation speed, and the smaller the flow area at the end of discharge process will exacerbate the liquid compression phenomenon.