Experimental and computational analysis of a R744 flashing ejector

In this paper we present a set of experimental data acquired on a CO 2 flashing ejector designed for ex- pansion loss recovery applications. Experimental results are compared with CFD simulations obtained us- ing a Homogeneous Equilibrium Model (HEM) and a recently developed mixture model that treats both the liquid and vapour phases as compressible and metastable materials. The models are implemented within a commercial CFD software via user defined subroutines. Pro and cons of each of the two ap- proaches are critically discussed in order to understand the relative performances in terms of numerical stability and accuracy. From this comparison, it can be shown that while the HEM is faster and intrinsi- cally stable, the mixture model has the potential to better reproduce the experimental data, especially in terms of mass-flow rates predictions.