Effect of Tin-Doped Copper Oxide Capillary-Porous Surfaces on Flow Boiling Performance of De-Ionized Water on Copper Heat Sink Minichannels

Abstract A cost-efficient sol–gel method was utilized to synthesize tin-doped copper oxide (Sn–CuO) capillary nanoporous coatings on copper substrates in this study. The micro/nanostructured surfaces exhibited superhydrophilicity and significantly enhanced boiling heat transfer in a confined minichannel environment. Compared to uncoated copper, the coated surfaces showed a substantial reduction in wall superheat at the onset of boiling. High-speed visualization revealed that the Sn-CuO coating facilitated frequent formation and rapid departure of small spherical bubbles, which enhanced liquid replenishment and heat transfer. Among the developed coatings, the Sn-CuO film annealed at 600 °C (Sn–CuO–600) demonstrated the best thermal performance. At a mass flux of 60 kg/m2s, the critical heat flux (CHF) improved by 64.21%, 168.1%, and 203% for coatings annealed at 500 °C, 550 °C, and 600 °C, respectively, compared to bare copper. The highest heat transfer coefficient (HTC) enhancement—up to 235%—was observed with the Sn–CuO–600 coating. The superior performance is attributed to enhanced surface wettability, reduced bubble departure diameter, and shorter bubble residence time, which collectively promote efficient heat removal. This work highlights the potential of integrating superhydrophilic Sn-doped CuO coatings with minichannel flow boiling to significantly improve heat transfer and delay CHF. The results provide valuable insights into the influence of surface micro/nanostructuring on boiling dynamics and support the development of high-performance thermal management solutions for compact electronic and energy systems operating under high heat flux conditions.