Numerical Investigations On Heat Transfer And Flow Characteristics Of Minichannel Heat Exchanger

Compared with traditional heat exchangers,minichannel heat exchangers with compact and high efficient features have become more and more popular in aerospace,automotive and other industrial applications.In this paper,the condensation heat transfer of refrigerants R134 a in rectangular minichannels is simulated by using the VOF model,the turbulence model and the phase transition model.This study numerically investigated the condensation heat transfer and flow characteristics under different mass flux.The condensation process is found to be enhanced with the increase of vapor quality and mass flux,while the friction pressure gradient decreases with the decrease of vapor quality and mass flux.For the liquid film distribution,in the lower vapor quality and mass flux,the liquid film is thinner in the upper part of the tube and the condensate converges to make the liquid film thicker in the bottom of the tube due to the effect of gravity.However,with the increase of vapor quality and the mass flux,the effect of gravity weakens and the liquid film is distributed more uniformly through the tube.In addition,this paper also studied the heat transfer and flow characteristics of parallel microchannel heat exchangers and manifold microchannel heat exchangers,compared the maximum temperature and temperature distribution of the heating surface under three different design schemes,and studies flow characteristics inside tminichannels.Simulation results show that the manifold microchannel has the best heat transfer effect and the lowest temperature rise on the heating surface.The manifold structure divides the microchannel into multiple sections in parallel,which effectively solves the problem of uneven temperature distribution on the heating surface.