A COMPARISON OF CRITICAL FLOW MODELS FOR ESTIMATING 2-PHASE FLOW OF HCFC22 AND HFC134A THROUGH SHORT TUBE ORIFICES

An experimental study to investigate the critical how of refrigerants through short tube orifices has been performed by measuring the mass f lowrates and pressure profiles along the short tube orifice. Eight cri tical how models have been examined and their results compared with th e experimental data for HCFC22 and HFC134a. These models include four homogeneous equilibrium models, two homogeneous frozen models, and two non-homogeneous equilibrium models. The data indicate that the how wa s choked when downstream pressures were lower than the saturation pres sure corresponding to the upstream temperature. The observed hows thro ugh short tube orifices included a lack of equilibrium due to short ti me of expansion and homogeneous mist how at the exit plane. These how trends would be more consistent with the basic assumptions of the homo geneous frozen models. Based on the comparison of the existing critica l flow models and experimental data, the homogeneous frozen models sho wed the best agreement with the measured data except for exit qualitie s below 0.06.