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The issue of regenerative cooling is one of the most important key technologies of flight vehicles, which is applied into both the engine and high-power electrical equipment. One pattern of regenerative cooling channels is the microchannel heat sinks, which are thought as a prospective means of improving heat removal capacities on electrical equipment of smaller sizes. In this paper, three numerical models with different geometric configurations, namely straight, zigzag, and sinusoid respectively, are built to probe into the thermal hydraulic performance while heat transfer mechanism of supercritical methane in microchannel heat sinks for the heat removal of high-power electromechanical actuator is also explored. In addition, some crucial influence factors on heat transfer such as inlet Reynolds number, operating pressure and heating power are investigated. The calculation results imply the positive effect of wavy configurations on heat transfer and confirm the important effect of buoyancy force of supercritical methane in channels. The heat sinks with wavy channel show obvious advantages on comprehensive thermal performance including overall thermal performance parameter ? and thermal resistance R compared with that of the straight one. The highest Nu and average heat transfer coefficient am appear in the heat sink with zigzag channels, but the pumping power of the heat sink with sinusoidal channels is lower due to the smaller flow loss.

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The maneuverability of flight vehicles and their significant working power cause high non-uniform heat flux in their electrical components. Meanwhile, the package structure of components leads to a hostile heat dissipation environment in which air cooling cannot be realized. Hence, in this paper, a numerical model for a wavy microchannel heat sink (MCHS) with secondary branches is proposed to enhance the thermal performance of heat sinks and improve the temperature uniformity of the substrates. Considering the symmetry structure of the heat sinks, the computational domain is constructed by two parallel sinusoidal channels with secondary branches on adjacent channel wall. The effects of geometric factors such as the cross-sectional opening degree and the arrangement of branches on the thermal performance of the heat sinks are studied. The results show that compared with the conventional wavy MCHS, that with secondary branches promotes fluid mixing efficiency, enhances thermal performance, and provides dynamic adjustment of the flow distribution. Furthermore, a heat sink with middle semi-opening branches shows superior thermal performance, while one with interlaced semi-opening branches shows better temperature uniformity of substrate. Meanwhile, an MCHS with secondary branches has a much larger Fc and a smaller entropy production rate ratio than that of a heat sink with no branches.

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