Topologically optimized mini-channel heat sinks for reduced temperature non-uniformity

Abstract

Water-cooled mini-channel heat sinks are widely used for thermal management of electronic devices, but their flow paths are usually limited to simple designs, such as parallel channels, due to manufacturing limitations. Such designs do not distribute flow uniformly, resulting in non-uniform heat transfer across the heat sink and significant temperature gradients. A liquid-cooled heat sink with a millimeter high flow channel was designed and fabricated to cool an 86 mm x 63 mm uniformly distributed heat load. A density-based topology optimization model was implemented in COMSOL to generate a non-traditional internal geometry that minimizes temperature non-uniformity. The topologically optimized heat sink was made using a novel thermal spray additive manufacturing method in which molten aluminum was sprayed into a cavity machined in an aluminum plate through a polymer mask made in the shape of the desired flow channels by 3D printing. The cavity was closed with an aluminum plate to create a sealed heat sink. The thermal performance of the topologically optimized heat sink was compared experimentally to that of a heat sink with parallel channels. Each heat sink was placed on a uniformly heated copper block dissipating 180 – 630 W (corresponding to heat fluxes of 3.3 – 11.6 W/cm2) and its temperature measured by an array of 9 thermocouples embedded in the heated heat sink face while water flowed through it at rates of 100–1500 mL/min. The optimized heat sink maintained lower surface temperatures and reduced temperature non-uniformity on its surface at all flow rates tested. Numerical simulations demonstrated that this was due to better flow distribution by the topologically optimized flow channels.