Numerical-experimental investigation of liquid slugging in the suction muffler of a hermetic reciprocating compressor

Abstract

Refrigerant in the liquid phase and lubricating oil that circulate in refrigeration systems may reach the compression chamber of compressors. This phenomenon of liquid slugging is detrimental to reciprocating compressors because it can damage valves and other components. A three-dimensional Eulerian multiphase model was developed using the software ANSYS CFX to predict the gas-liquid flow in a simplified suction muffler geometry. In addition, an experimental bench was designed to allow the injection of specified volumes of lubricant oil into the suction muffler and measurement of the volume that reaches the muffler outlet. The liquid slugging was observed through glass windows positioned in the test section and recorded with a high-speed camera. Measurements showed that the phenomenon of liquid slugging is random and that the volume of liquid reaching the muffler outlet increases with the oil injection pressure. The numerical model was able to predict the oil volume that reaches the muffler outlet in agreement with measurements in the case of high injection pressures, but it overpredicted the volume when the injection pressure was decreased. The visualization showed changes in the liquid phase morphology that are difficult to predict since closure models for a two-fluid model are typically developed for dispersed morphology.