Interfacial Thermophysics of Pool Boiling on Hierarchical Micro-/Nanoporous Copper Surfaces

A thermophysically driven experimental investigation is presented on nucleate pool boiling from hierarchically structured copper surfaces with independently controlled micro- and nanoscale features. A parameter-decoupled electrochemical etch–anodization process was used to fabricate three surfaces (S1–S3) with systematically varied micropit diameters (1–5 μm), nanopore sizes (50–150 nm), and areal porosity (20–52%), enabling isolation of morphology-induced interfacial transport mechanisms. Surface topology, wettability, and capillary wicking behavior were quantified and correlated with saturated pool boiling performance. Compared with smooth copper, the structured surfaces significantly modified boiling incipience, bubble dynamics, and heat transport. The intermediate-porosity surface (S2) exhibited a pronounced reduction in the onset of nucleate boiling superheat ([Formula: see text]), accompanied by an order-of-magnitude increase in active nucleation-site density and a twofold increase in bubble departure frequency, indicating reduced nucleation energy barriers and enhanced microlayer evaporation. In contrast, the high-porosity surface (S3) achieved the maximum critical heat flux enhancement ([Formula: see text], [Formula: see text] at [Formula: see text]), attributed to capillary-assisted liquid replenishment and delayed hydrodynamic instability. A morphology-informed semi-empirical correlation predicts the heat-transfer coefficient and critical heat flux within [Formula: see text] accuracy.