Two-phase refrigerant distribution in a parallel flow minichannel heat exchanger having lower combining/dividing header

Abstract

Brazed aluminum heat exchangers are recently considered as evaporators of automotive or residential air conditioners. In this case, it is very important to distribute the two-phase refrigerant (especially the liquid) evenly into each tube. In this study, R-410A distribution in a two pass evaporator with upper horizontal combining-dividing header was investigated. Tubes were heated to yield a test section outlet superheat of 5oC with inlet quality of 0.2. The number of tubes was 10 for the inlet pass and 12 or 14 for the outlet pass. For each case, mass flux was varied from 73 kg/m2s to 143 kg/m2s. In the combining/dividing header, two-phase mixture out of the inlet pass is first merged and then re-distributed to the outlet pass. More liquid is forced downstream as mass flux or quality increases yielding better flow distribution. Effect of insertion device in the inlet header was also investigated. Efforts were made to develop correlations to predict the liquid or gas distribution in a header with limited success. Header pressure drop data are also provided.