Micro-structure resolved dual-parameter model of Kelvin metal foam enabling airfoil-inspired skeleton optimization: towards enhanced comprehensive heat transfer performance

Open cell Kelvin metal foams are attractive for compact heat exchangers owing to their large specific surface area and structural regularity. However, their broader use is limited by their inherently high flow resistance and the absence of models that can directly characterize the thermo-hydraulic performance of metal foam. In this context, this study develops a dual-parameter analytical model that relates the effective thermal conductivity of open cell Kelvin metal foams to skeleton radius and skeleton length. The model is validated via steady-state conduction simulations, with an average deviation of 4.34%. Based on this model, sensitivity analysis shows that the skeleton cross-sectional geometry has a much stronger influence than skeleton length. This motivates an airfoil-inspired redesign, in which cylindrical skeletons are reshaped into elliptical sections with aspect ratio b/c to reduce flow resistance. Conjugate heat-transfer simulations and experiments are conducted to evaluate how the aspect ratio b/c affects flow resistance and thermo-hydraulic performance. The results show a rise-then-fall trend in comprehensive heat transfer factor η with increasing b/c, with an optimum at b/c = 1.4, where the factor η is improved by 10.38% relative to a circular section and by up to 53.90% compared with b/c = 3.2. Pressure-drop experiments agree with simulations within 5.3%–5.6%, supporting the reliability of the predicted hydraulic trend caused by strut-shape optimization. This work provides a micro-structure resolved design basis for next-generation Kelvin metal foam heat exchangers with improved efficiency and reduced flow resistance.