CFD Analysis of R744 Ejectors

Abstract

Ejector systems have been applied for many decades in refrigeration systems and this is still a very active field of research. More recently, ejector technology has been applied to transcritical refrigeration systems. Pressure energy recovery is particularly interesting for R744 refrigeration and heat pump technologies compared to conventional refrigerants, since a relatively larger fraction of the cycle losses are related to throttling losses. Some of the Japanese heat pump water heaters do apply ejectors in transcritical units with R744 as the working fluid.The new test facility of SINTEF/SUT in Trondheim makes it possible to experimentally investigate a wide range of ejectors and detailed measurement results are obtained. The design of specific ejectors is an on-going task for the research team at SINTEF.Identification of internal ejector losses are important when developing new ejector concepts. When applying CFD analysis, these losses can be identified and possibly reduced to a minimum value.The objective of the project work is to adapt a CFD ANSYS model to the measured ejector geometries. Thereafter a detailed loss analysis of the existing ejectors can be performed and suggestions for performance improvement can be given.