A Simulation Study on Two-Phase Microchannel Evaporator Header Distribution Using Computational Fluid Dynamics Header Model and Segmented Heat Transfer Tube Model

One of the major challenges in Microchannel Heat Exchanger (MCHX) design is the flow mal-distribution from the header into different flow passes, especially for evaporator applications with two-phase refrigerant. Computational Fluid Dynamics (CFD) simulation is extensively used in the heat exchanger design processes and performance evaluations. The Eulerian Multiple Flow Regimes model in STAR-CCM+® modeling environment combines the benefits of the commonly used Volume of Fluid model and Eulerian Multiphase model. This newly available model allows simulation to capture free surfaces, dispersed sprays and dispersed bubbles. R-32 is selected in this study as it is widely used in split type air conditioners and heat pumps. Two different geometries are analyzed: flow pattern verification in round tube and microchannel heat exchanger header. The header simulations are validated again experimental test data and thermal infrared image. The CFD two-phase distribution results were then used as an input of a segmented heat transfer tube model to account for air-to-refrigerant heat transfer. This study should provide researchers and engineers a concreate example in setting up flow distribution analysis for designing improved microchannel heat exchanger headers