Enhancement of liquid cooling in microchannel heat sinks: numerical and experimental assessment of progressive geometric optimisation

The increasing power density of modern electronic devices and high-power energy systems requires liquid-cooling solutions capable of dissipating high heat fluxes while maintaining acceptable pressure losses and temperature non-uniformity. Microchannel heat sinks (MCHSs) are promising for this purpose, but many published studies focus either on isolated channel configurations or on highly specific optimised layouts, with limited attention to the progressive transition from simple channel geometries to complete cooling plates with realistic flow distribution conditions. In this work, the thermo-hydraulic performance of several MCHS configurations was investigated through a combined numerical and experimental approach, covering straight rectangular and trapezoidal channels, aligned and misaligned cross-hatch geometries, and complete heat sink plates with ramp-assisted inlet/outlet manifolds. The objective was to determine how progressively more complex channel and manifold geometries modify pressure drop, heat transfer, and temperature uniformity, and whether these trends remain valid when moving from isolated channels to full cooling-plate configurations. The analysis was conducted under laminar single-phase flow for Reynolds numbers between 100 and 1,000. The results showed that trapezoidal channels reduced pressure drop relative to equivalent rectangular channels, while cross-hatch and especially misaligned cross-hatch configurations enhanced temperature uniformity and heat transfer by promoting flow mixing and repeated redevelopment of the thermal boundary layer. Laser microfabrication was used as a flexible route to produce and experimentally assess selected geometries, and the comparison between measurements and numerical predictions showed reasonable agreement while correctly capturing the main thermo-hydraulic trends. Overall, the study provides a physically interpretable design framework linking simplified channel-level analysis to realistic manifolded cooling-plate behaviour, which may support the development of improved liquid-cooling solutions for high-heat-flux electronics cooling applications.