Study on the uneven flow distribution and non-uniform heat transfer in microchannels

The power module is one of the main heating sources with non-uniform heat flux in high-power electrical servo systems used for flight vehicles. Faults in the power module are usually caused by a high or a non-uniform temperature. Given the environment of heat dissipation during flight, a regenerative cooling method is typi-cally used, and the cooling system is designed as a microchannel heat sink with supercritical fuel. This is an effective means of solving thermal problems in the flight vehicles. However, because of the high heating power and non-uniform heat distribution of the power module, it is necessary to optimize its heat sink to restrict the high temperature rise and suppress the non-uniform distribution of temperature. In light of these considerations, a 3D numerical model of the microchannel heat sink of a power module with non-uniform heat flux was established in this study to examine the heat transfer and the thermal performance of the cooling channels. Based on the validation of the mesh and numerical method, the simulations of the flow distributions of the channels were performed to assess the thermal performance of the heat sink. It included investigating the effects of the inlet location of the manifold and its injection angle on the flow distribution in the channels, and the influences of the flow distribution and the operational parameters on the thermal performance of the heat sink. The results revealed that the Z30 configuration provided the best location and injection angle of the inlet to match the non-uniform heat flux of the power module. In this case, the values of Stanton number and buoyancy parameter of channel 4 yielded the minimum values of all channels owing to its higher flow rate and gradual rise in tem-perature. The deviation in the rate of mass flow phi changed slightly corresponding to the various operational parameters, only the total heat flux would bring a bigger fluctuation. The tiny difference in temperatures among the observation areas on the substrate verified the positive influence of the flow distribution in matching the non-uniform heat flux.