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.