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 5 o C 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/m 2 s to 143 kg/m 2 s. 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.

Effect of row-crossing header configuration on refrigerant distribution in a two row/four pass parallel flow minichannel heat exchanger

“…Better flow distribution was obtained at high mass flux or low quality. Byun and Kim [16] investigated the flow distribution in a vertical two pass evaporator having horizontal headers using R-410A. Tubes were heated to yield outlet quality 0.6 and 1.0 with inlet quality fixed at 0.2.…”