Numerical investigation on vapor-liquid two-phase compression in the cylinder of rotary compressors

Abstract

Liquid slugging often appears during the process of start-up and defrost due to the existence of liquid in the compression chamber. As the pressure shoots up to a very high values under the liquid slugging conditions, it threatens the reliability of rotary compressors. In this paper, a newly developed model to predict the pressure jump in the cylinder during the liquid slugging conditions is proposed, and two-phase compression characteristics are investigated. This model considers refrigerant phase change, kinetic energy of refrigerant and heat exchange between refrigerant and the wall of compression chamber. Comparisons are made with experimental study of liquid slugging using R290 refrigerant. The simulation results show good agreement with experimental results in terms of pressure variation. Effects of initial gas fraction, rotation speed of crank and types of refrigerant on the liquid slugging are investigated. This study shows that by reducing rotation speed or increasing the gas fraction, the pressure jump in the cylinder can be effectively eliminated. It also shows that liquid slugging in the cylinder using R290 is weaker than R22 and R410A under the same conditions.