Experimental and numerical studies of header design and inlet/outlet configurations on flow mal-distribution in parallel micro-channels

Abstract

The present study concentrates on the effects of header design on flow mal-distribution in a micro-channel (25 channels) heat sink. Experiments have been conducted to investigate the effect of header shape (rectangular and triangular) on flow mal-distribution and the manufacturing tolerances along the channel length and between the channels. Detailed numerical simulations have been performed for different geometric configurations by varying the header shape (rectangular, trapezoidal and triangular), header size and locations of inlet and outlet (I, C, V, Z and U-type) arrangements. Predicted results clearly illustrate that flow separation and recirculation bubbles occurring in the inlet header are primary responsible for the flow mal-distribution between the channels. To quantify the mal-distribution through the channels, the channel-wise flow rate predicted at the channel inlets and the mal-distribution factor has been compared for all the cases investigated in the study. Results highlight that flow distribution is better for C-type and poor for V-type flow configurations. An I-type flow arrangement has a symmetrical flow distribution pattern with a large pressure drop and U-type flow has a minimal pressure drop. It is observed from the header shape analysis that a triangular inlet header provides better flow distribution; whereas, for the case of an outlet header, the trapezoidal header provides uniform flow distribution. Predictions show that mal-distribution decreases with header width and for the range of header depths considered in the study, there exist an optimum header depth (7 mm) in which the flow distribution, pressure drop, and mal-distribution factor is better. Predicted results agree well with the measured experimental data.