Numerical evaluation of a solar-assisted jet-ejector refrigeration system: Screening of environmentally friendly refrigerants

Abstract

The present paper evaluates numerically the feasibility of a solar jet-ejector refrigeration system from an efficiency maximization perspective with three low environmental impact refrigerants, namely, R1234yf, R1234ze and R600a. Special emphasis is given to the jet-ejector internal geometry optimization as a mechanism to improve the overall cycle performance. The jet-ejector entrainment ratio in different operating conditions and geometric configurations is determined by using a Computational Fluid Dynamics (CFD) approach experimentally validated which includes real gas models of R1234yf, R1234ze and R600a. R1234yf exhibited the best performance in terms of overall system efficiency closely followed by R600a and R1234ze. This suggests that the influence of the working fluid can be considerably mitigated if a thorough design of the jet-ejector is carried out. Afterwards, the refrigerant R1234yf is selected to carry out sensitivity studies with different collector typologies and solar irradiation scenarios. The Evacuated Tube Collector (ETC) model provided the highest overall system efficiency (ηov=0.213) for the peak solar irradiation (1000 W/m2). Nevertheless, one of the Parabolic Trough Collectors (PTC) models under investigation offered the most robust performance if a wider range of solar irradiation scenarios is considered.