An experimental investigation of a R-134a ejector refrigeration system

•Experimental results for the critical point of a R-134a ejector refrigerator.•Influence of the nozzle position and superheating on the mass ratio.•Study of two geometries with secondary throat to enhance pressure recovery.•Performance analysis comparison based on a dimensionless parameter.

The present study reports the results of an investigation of an ejector refrigeration system working with refrigerant R-134a, aiming at the enhancement of the pressure recovery. The critical condition has been determined for three mixing chambers of equal internal diameter but different profiles and for several stagnation conditions of primary and secondary fluid. The influence of both the nozzle longitudinal position and the vapor superheating of the primary and secondary fluid stagnation states on the mass ratio has also been reported. Experimental results have shown a negligible performance increment of the new mixing chamber designs, “B” and “C”, with respect to a standard design one, “A”, with the mixing chamber “C” underperforming the other two over all the performed tests. A new performance parameter has been introduced being defined as the ratio between experimental and a 2nd law based theoretical mass ratio.