Impact of Two-Stage Copper Oxide Nanowire Coatings on Flow Boiling Heat Flux in Mini-Channel Heat Sinks

Abstract Effective thermal management has emerged as a significant challenge in electronics and power systems subject to high heat flux. This study aims for the enhancement of flow boiling heat transfer performance by synthesizing novel hybrid copper oxide nanowires (CuONWs) on copper mini-channel substrates. A two-stage aligned hybrid CuONW architecture was developed, in which distinct layers of nanowires are fabricated with different structural features, each contributing uniquely to the enhancement of boiling performance through complementary mechanisms. This innovative high-density two-stage configuration minimizes fluidic resistance by addressing the limitations of sparse and discrete nanostructure grids, thereby effectively controlling the wicking capabilities of the hybrid nanowires. The experimental results demonstrated significant enhancements in flow boiling performance. Notable enhancements involved an earlier onset of nucleate boiling and an improved heat transfer coefficient. For low flowrate conditions (73 kg/m2s) on CuONWs-600-700-coated surfaces, the heat transfer coefficient and critical heat flux were increased by approximately 230% and 198%, respectively. These enhancements are attributed to the superhydrophilic nature of the nanostructures, increased capillary-driven wetting, the availability of a broad distribution of nucleation sites, and the promotion of an annular flow regime.