refrigeration, two-phase, ejector, COP, R134a
The aim of the present work is to experimentally study the possibility of improving the energy efficiency of a vapour compression refrigeration system where a two-phase ejector replaces the expansion valve. A test bench using refrigerant R134a was designed and built which functions in both the conventional mode and in ejector mode. The primary nozzle of the ejector was equipped with a double throat, having an adjustable area for the first throat and a fixed area for the second throat. Experimental results showed an improvement of 11% in the coefficient of performance (COP) in ejector mode as compared with the conventional mode. The role of the double throat in the primary nozzle as well as the behaviour of the pressure ratio and entrainment ratio parameters are discussed. A modified ejector refrigeration system using two evaporators is proposed as a means of improving the control stability and addressing the separator effectiveness limitations.