Effect of Motive Nozzle Exit Position in a R-744 Two-Phase Ejector

Abstract

Ejector expansion transcritical refrigeration systems, in general, have an advantage over conventional transcritical refrigeration systems. In this paper, a CFD-based investigation of transonic flow phenomenon for R-744 inside a three-dimensional model of an ejector is presented. Real-gas thermophysical properties of R-744 such as the density, dynamic viscosity, and thermal conductivity are defined as a function of pressure and temperature based on NIST Refprop. Three different motive nozzle exit positions are investigated. A motive nozzle tip position that is near to the mixing section is found to have higher pressure and lower Mach number due to better mixing.