Numerical Study of Semi-Circular, Triangular, and Rectangular Roughness in Microchannels

Modern electronic devices generate heat fluxes that often exceed the capabilities of conventional cooling methods such as passive heat sinks and air cooling. Microchannel heat sinks offer an effective alternative due to their high surface-area-to-volume ratio, but most numerical studies assume perfectly smooth channel walls, despite the unavoidable surface roughness introduced by fabrication processes. This work numerically investigates the influence of idealized surface roughness on heat transfer and pressure drop in a copper microchannel heat sink cooled by water. Three roughness geometries—semi-circular, triangular, and rectangular—are examined using a two-dimensional, laminar, non-isothermal conjugate heat-transfer model implemented in COMSOL Multiphysics. A smooth-wall microchannel is first simulated as a reference case and shows good agreement with established single-phase microchannel correlations. Relative to the smooth channel, all roughened configurations enhance local fluid velocity and disrupt the thermal boundary layer, resulting in improved heat transfer at the expense of increased pressure drop. The triangular roughness provides the best thermal performance, yielding the lowest peak fluid temperature of approximately 295 K, while the rectangular roughness shows the weakest cooling enhancement. The results highlight the trade-off between thermal performance and pumping power and identify roughness geometries that offer effective cooling without excessive hydraulic penalties.