Copper nanowires to enhance flow boiling at low mass flow

In this study, nanowires (140 nm, 250 nm, and 350 nm in diameter) were fabricated on copper substrates to enhance the flow boiling performance of ethanol, targeting thermal management of high-heat-flux electronics. Flow boiling was experimentally investigated at low mass flow rates of 14.4 kg/(m2·s) and 19.8 kg/(m2·s), focusing on bubble dynamics, heat transfer coefficient, and pressure drop. The results show that the nanowires significantly increase nucleation site density and bubble departure frequency, while suppressing early bubble coalescence and delaying the onset of vapor film formation. Nanowire substrates with a diameter of 350 nm demonstrate superior fluid boiling performance compared to nanowires of other diameters. Heat transfer performance increases by 36% relative to that of a smooth copper substrate. The pressure drop increases by 7.4% with 350 nm nanowires compared with a smooth copper substrate. The study confirms the potential of nanowires to augment flow boiling at low mass flow rates with acceptable pressure drop, and that nanowire diameter optimization effectively modulates overall performance. These findings provide both theoretical support and practical guidance for the micro- or nanoscale-structured design of compact thermal management systems for electronic devices.