Experimental investigation of transient fluid flow and superheating in the suction chamber of a refrigeration reciprocating compressor

The gas superheating that takes place along the suction path of refrigeration compressors considerably decreases their volumetric and isentropic efficiencies. This paper reports an experimental investigation of transient fluid flow and superheating in the suction chamber of a 3600 rpm refrigeration compressor under two operating conditions. Hot-wire and cold-wire probes are applied to measure velocity and temperature transients, whereas measurements of pressure pulsation are acquired with a piezoelectric sensor. The results reveal a very complex phenomenon with steep variations in all flow parameters during the operation cycle. Significant superheating is observed during the period in which the suction valve is closed, suggesting high rates of heat transfer between the gas and the chamber walls. It was observed that the opening of the valve leads to a steep temperature drop in the suction chamber due to both the associated gas expansion process and the supply of fresh gas from the suction muffler.