Numerical simulation of phase separation in the second header of microchannel condenser

Microchannel condensers with separation circuiting have been proved to increase condenser effectiveness. In the vertical second header, liquid separates from vapor mainly due to gravity, leaving vapor-rich flow with higher heat transfer coefficient to go upward into more microchannel tubes. Separation is usually not perfect, expressed through the separation efficiency. This paper presents the numerical study of phase separation efficiency. The Eulerian multiphase model of Euler-Euler approach of Computational Fluid Dynamics (CFD) is used. The two-phase refrigerant R-134a for mobile air conditioning (MAC) application is simulated. The inlet mass fluxes to the second header are 166 kg·m-2·s-1, 207 kg·m-2·s-1 and 311 kg·m-2·s-1. The inlet quality is in the range of 0.16 – 0.21.Simulation agrees well with the experiments. The CFD results are also compared to a 1-D numerical model previously built by the authors and a good agreement has been found. Conclusion can be drawn that liquid separation efficiency ?l decreases with increasing vapor separation efficiency ?v following a linear trend in the experimental range. Reversed flow can be seen in the cross section of the header.