Effect of inlet configuration on the refrigerant distribution in a parallel flow minichannel heat exchanger

The refrigerant R-134a flow distribution was experimentally studied for a round header/ten flat tube test section simulating a brazed aluminum heat exchanger. Three different inlet configurations (parallel, normal, vertical) were investigated. Tests were conducted with downward flow for mass flux from 70 to 130 kg m−2 s−1 and quality from 0.2 to 0.6. Tubes were flush-mounted in the test section, with no protrusion into the header. It is shown that normal and vertical inlet yielded similar flow distribution. As mass flux or quality increased, however, better results were obtained for normal inlet configuration. The flow distribution was worst for the parallel inlet configuration. Possible explanation is provided based on flow visualization results. Correlations were developed to predict the fraction of liquid or gas taken off by downstream channel as a function of header gas Reynolds number at immediate upstream.