Liquid Jet Impingement on Mesoscale Modified Surfaces for Power Electronics Cooling
Type of DegreePhD Dissertation
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In each vehicular generation, active safety and comfort features are added and enhanced, increasing the power draw required to operate every feature. As a result, heat generation in the power electronics is increasing, and it is anticipated that traditional, passive heat sinks will be insufficient to maintain the devices within operating conditions. Due to limited space under the hood, jet impingement cooling is a promising approach for active thermal management. Jet impingement on the backside of the substrate, a region with no components, can be applied with minimal added components under the hood and at flow rates and pressure losses in the range of those already achieved in the radiator flow loops of the current automotive generation. In jet impingement cooling, one or more columns of a working fluid are directed normal to a heated surface, naturally mitigating the development of the thermal boundary layer. In doing so, jet impingement can achieve highly efficient, single-phase heat dissipation from the surface. To achieve best performance across a surface, an array of jets can be applied. Interactions between these jets can provide thermal improvements in regions away from the jets, but spent fluid must be managed appropriately, otherwise it will negatively impact downstream performance. The present effort investigates mesoscale cone and rib structures on the impingement surface engineered to promote desirable flow interactions while providing additional surface area for heat dissipation. Each of these modifications were applied under both a flat and angled confining wall, the latter of which allowed spent fluid to reach the outlet without affecting jets downstream. Each of these geometries were investigated experimentally using particle image velocimetry flow visualization to examine the effects of the modifications and wall angles on the flow behaviors. This was paired with a numerical model in ANSYS Fluent, which also provided insight on thermal performance across the surface.