Effect of inlet configuration on upward branching of two-phase refrigerant in a parallel flow heat exchanger

The refrigerant R-134a flow distributions were experimentally studied for a round header-10 flat tube test section simulating a brazed aluminum heat exchanger. Three different inlet orientations (parallel, normal, vertical) were investigated. Tests were conducted with upward flow for the 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 header with no protrusion. Both for liquid and gas, the best flow distribution was obtained from vertical inlet configuration. Between other two inlet configurations, parallel inlet was better for liquid distribution, and normal inlet was better for gas distribution. In general, the effect of mass flux or quality on flow distribution was not significant. Correlations were developed to predict the fraction of liquid or gas taken off by downstream channel as a function of header liquid Reynolds number at immediate upstream. Header pressure drop was obtained by subtracting appropriate pressure drops from the measured pressure drop. The header pressure drops were mostly negative, which implied that the pressure was recovered in the header.