Experiment and visualization of R410A flow distribution within the vertical header of microchannel heat exchanger.

This paper reports an initial step to obtain an equally distributed fluid flow in an evaporator heat exchanger and eventually increase its performance. Experiments are carried out for R410A, using a vertical header where 20 horizontal parallel flat tubes are connected and the protrusion depth is half of the header width. The flow enters the header from a bottom inlet port and there is no heat load applied on the flat tubes. Inlet vapor quality before the header is varied for a fixed total mass flow rate of 60 kg/h. For each set of conditions, the mass flow rate and quality at different vertical positions of the header are singularly measured. Visualization data and experimental results have shown that 0.6 vapor quality before the header produces a more even distribution having a more homogeneous two-phase flow compared to 0.2 where phases are distinctly separated yielding dryouts on the top channels.

本研究报道了实现蒸发器换热器内流体均匀分布、最终提升其换热性能的初步探索工作。实验以R410A为工质，采用立式集管，该集管连接20根水平平行扁平换热管，且集管凸起深度为其宽度的一半。流体从底部入口端口流入集管，扁平换热管未施加热负荷。在总质量流量固定为60 kg/h的条件下，调节集管前的入口蒸汽干度。针对每组工况，分别测量集管不同垂直位置处的质量流量与干度。可视化数据与实验结果表明：当集管前入口干度为0.6时，流体分布更为均匀，两相流均一性更佳；而干度为0.2时，两相发生明显分离，顶部通道出现干涸现象。