Application of CFD Models to Two-Phase Flow in Refrigerant Distributors

Abstract

The goal of the work described in this paper was to identify an appropriate CFD model for refrigerant distributors and to apply the model to develop improved designs. There appears to have been no previous work applying CFD to two-phase flow in refrigerant distributors. As a first step, results of predictions using different two-phase modeling approaches available within commercial CFD codes were compared with experimental results from the literature for two-phase flow distribution with air and water as working fluids. The volume of fluid (VOF) and algebraic slip mixture (ASM) models failed to predict the experimental data available, whereas the inter-phase slip algorithm (IPSA) model predictions were in close agreement with the measurements in all cases. However, for a typical refrigerant distributor geometry and set of operating conditions, predictions of two-phase distribution and separation were quite similar for the different modeling approaches. As a result, the ASM is applicable for studying refrigerant distributor designs and was used to evaluate the performance of both existing and improved designs. In general, it is better to utilize a spherical distributor base as compared with other shapes and to locate the orifice close to the distributor base. These changes tend to improve the robustness of the distributor in terms of providing even flow and phase distribution in different outlet branches when the orifice and/or distributor are not oriented optimally. In addition, experiments were performed that tend to validate the general trends associated with the CFD results for refrigerant distributions.