High-heat-flux liquid cooling of electronics with manifold microchannels: Thermal-hydraulic optimization and experimental validation

Rising power densities in power electronics demand cooling solutions that can sustain high local heat fluxes while maintaining low thermal resistance and high energy efficiency. This work presents the design, computational fluid dynamics (CFD)-based optimization, and experimental validation of a single-phase liquid cooled copper U-type manifold microchannel cooler (MMC) for high-heat-flux power electronics. A conjugate heat-transfer CFD framework, driven by multi-point hotspot heat maps, is used in a sequential multi-objective optimization of manifold and microchannel geometries to minimize junction-to-fluid thermal resistance and pressure drop, thereby maximizing coefficient of performance (COP). The resulting optimized MMC geometry is then fabricated and experimentally characterized using discrete GaN devices on a PCB as heat sources in an indirect-cooling configuration. Across flow rates of 0.5-6 L min −1 , the optimized design reduces pressure drop by 70–98% and lowers average thermal resistance by 19–26% relative to its baseline MMC design, while increasing COP by up to 74 × for a comparable heat removal rate. The optimal cooler design dissipates heat fluxes up to 208 W cm −2 with COPs as high as 1.6 × 10 6 and low thermal resistance. Extrapolation of the measured performance to a 75 mm × 75 mm package footprint indicates a junction to coolant thermal resistance as low as 3.5 K kW −1 , providing substantial thermal headroom for multi-kilowatt power modules and GPU-class packages. Our work demonstrates that single-phase liquid cooled copper MMCs designed using Pareto-based optimization in an indirect-cooling configuration provide a practical, high-COP solution for high-heat-flux electronics. • Hotspot-driven multi-objective numerical optimization of U-type manifold microchannels. • Optimization targets enhanced thermal-hydraulic performance with improved COP. • Experimental validation using discrete GaN power devices as heat sources. • Sustained single-phase cooling up to 208 W cm −2 with COP up to 1.6 × 10 6 . • 70-98% lower pressure drop, 19-26% lower thermal resistance, and up to 74 × COP improvement compared with baseline MMC designs.