Critical heat flux model based on transient wicking governed by bubble dynamics on electrodeposited porous copper surfaces

Next-generation nuclear reactors and advanced high-performance electronic devices generate extremely high heat fluxes, requiring highly efficient cooling technologies. Boiling heat transfer is a promising solution; however, its performance is fundamentally limited by the critical heat flux (CHF). In this study, a copper porous material fabricated by electrodeposition was applied to a heating surface to enhance CHF during saturated pool boiling of water. Compared with a plain surface, the CHF was increased by a factor of 4.4 under atmospheric pressure and 3.7 under reduced pressure (15 kPa). The CHF enhancement correlated strongly with the wickability (capillary liquid absorption capability) of the porous material, indicating that capillary-driven liquid supply plays a key role. Nevertheless, the measured CHF could not be explained by conventional steady-wicking-based models, which assume continuous liquid supply and neglect the inherently unsteady nature of boiling. To address this limitation, a new CHF prediction model is proposed that explicitly incorporates transient wicking governed by bubble dynamics. The model accounts for the temporal restriction of liquid supply caused by bubble residence on the heating surface and provides a physically grounded description of CHF enhancement on porous materials. The proposed model predicts the experimentally measured CHF within 20% accuracy over a wide range of conditions, including variations in pressure, heater size, and porous thickness and morphology. These results demonstrate that transient, bubble-governed wicking is essential for accurately modeling CHF on porous heating surfaces.