Experimental and numerical investigation of flow maldistribution in a circular microchannel heat exchanger at various flowrates

Configuration of the microchannels connection to the manifold in microchannel heat exchangers significantly influences flow uniformity in the microchannels and significantly affects the even thermal dissipation to the surroundings. This paper presents the uniformity anxieties of the flow through a non-protruded microchannel heat exchanger that has been explored experimentally and numerically. The prototype consisted of 5-mm-diameter inlet and outlet headers with 20 microchannels of 0.96-mm-diameter and 50-mm-long with no protrusion depth. The velocities were measured by particle image velocimetry at 308 and 617 ml/min flow rates, corresponding to Reynolds numbers of 1500 and 3000 based on the header diameter. Using ANSYS FLUENT, a CFD simulated the flow in the microchannels heat exchanger at Reynolds numbers of 1500, 3000, 4500, 6000, and 7500, allowing a detailed flow field visualization. The numerical procedure was validated by comparing the simulation velocity results with the experimental results, showing a mean relative error of all the 20 microchannels of 3.8% and 8.2% for flow rates of 308 and 923 ml/min, respectively. Both experimental and numerical results show that the microchannels' velocity distribution is not uniform at the last few microchannels. The present work results support the concept of a protruded microchannel that produces better uniform flow. Hence, extended investigations are recommended to explore the effect of the channel's protrusion on flow uniformity and address the high inconsistency in the pressure drop prediction. Also, the simulation could be beneficial if extended to compare the maldistribution with various manifold diameters.