MICRO HEAT SPREADERS BASED ON MICROCHANNELS FOR CONCENTRATED HEAT FLUXES ON SPACECRAFT SUBSYSTEMS

摘要

A micro heat spreader (MHS) is a micro-fluidic device designed for thermal management of electronic components by means of controlled liquid convection in a closed loop. In contrast to classical fluid loops, the design and the optimization of a micro heat spreader is complex. It requires an adaptation and a good understanding of the fluid dynamic behaviour at this subscale-level along with the fabrication process of micro electro-mechanical systems. Based on analytical predictions, this new approach would increase the heat dissipation with an order of magnitude compared to passive cooling strategies. First, an overview will be given of what has been studied and developed so far on heat exchangers and micro-heat spreaders for dense heat fluxes. Their applicability towards a spacecraft environment will be assessed. Secondly, under design/optimisation aspects, where massive numerical tools are not applicable, engineering approximations based in simplified methods and engineering correlations need to be developed. Classical engineering correlations do not always seem to be applicable for micro-fluidic devices, and new ones from computational or experimental fluid dynamics (CFD and EFD respectively) have been obtained. Simple models featuring the physical behaviour of the MHS allow for sensitivity analysis of geometrical and operational parameters, driving to an optimum design. Finally, a MHS prototype based on microchannels, designed along the above mentioned considerations as a test demonstrator and using single phase fluid, will be discussed. Previously a less exigent design aimed to visualisation, rig calibration and priming process studies have been tested.