Abstract: Aiming at solving the problem of non-uniform heating mode from power module caused by the different heating dissipation of components, the numerical model of microchannel heat sink with multi-structure on flight vehicle actuator is built considering the actual structure and working conditions of power module, and based on the validation test of numerical model and mesh independent, the circumferential heat transfer mechanism of microchannel at the typical non-uniform heating region and the overall thermal performance of heat sink are investigated respectively by FLUENT. The simulation results reveal that under the same cross-section shape of microchannels, the non-uniform temperature distribution of inner wall in microchannels is demonstrated circumferentially, and the identity of heat transfer coefficient of observed lines in the corresponding position of different channels is verified. Under the constant flow area, the channel number and geometric structure play an important role on local thermal performance, viz. the matched-degree of the effect factors such as the non-uniform heat flux distribution, the flow direction of coolant and the channel geometric structure can improve the temperature uniformity of substrate obviously. The channels with decrement cross section structure from high heat flux region to the lower one and the structure with more channels and smaller sizes, have the lower overall thermal resistance and better temperature uniformity of substrate.

Key words: power module, electrical servo system, microchannel heat sink, non-uniform heating, heat transfer characteristics, structure optimization