CFD Analysis of Refrigeration Cycle Ejector

Abstract

The use of ejector cycles for increased performance and efficiency is becoming more prevalent in industry. The goal of this study is to evaluate an ejector using Computational Fluid Dynamics (CFD) to evaluate flow patterns, perform trade studies varying the type of refrigerant, and determine the entrainment ratio for each working fluid, over a range of boundary condition pressures, set at points along the ejector’s flow path. The 2012 Toyota Prius V is one of the first automobiles using an ejector cycle in their internal cabin refrigeration system. The DENSO Corporation ejector hardware was used as the basis for the creation of geometry for the CFD mode of the ejector. Three working fluids were simulated, R-134a, R-245fa, and R-1235yf. The primary findings of this study were as follows. The CFD study here indicates that R-245fa performs the best out of the three working fluids, when examining their entrainment ratios (ratio of secondary to primary flow rates in the ejector). For all three working fluids, the entrainment ratio was seen to peak performance at an ejector inlet pressure of 1.75 × 105 Pa. The ejector mixing chamber pressure and ejector outlet pressure boundary conditions also witnessed a rise in entrainment ratios, during an increase of their respective pressure values.