Pore-scale conjugate heat transfer analysis of turbulent flow over stochastic open-cell metal foams

Fundamental understanding of turbulent flow and heat transfer in composite porous-fluid systems, which consists of a fluid-saturated stochastic open-cell metal foam and a flow passing over it, is crucial for fostering technological development in numerous applications such as transpiration cooling in aerospace, packed-bed thermal storage and thermal management of electronic devices. In this work, conjugate heat transfer simulations were adopted to explore the turbulent flow and heat transfer features in a composite porous-fluid system at the pore scale. Simulations were performed to account for the influence of the blockage ratios (i.e., BR = 0.5, 0.8 and 1.0) on pressure drop and heat transfer rate by introducing a new concept called penetration cooling length. Furthermore, the effect of Reynolds numbers (i.e., Re = 1800, 3600 and 7200) at different blockage ratios was investigated in terms of pressure drop, fluid and solid temperatures, interstitial heat transfer coefficient, and flow leakage. Results indicate that for a fixed blockage ratio, as the Reynolds number increases by a factor of 3.0, there is a 14.9-fold increase in the pressure drop and a 2.9-fold increase in the interstitial heat transfer coefficient. Additionally, for a fixed Reynolds number, when the blockage ratio increases by a factor of 2.0, there is a 6.8-fold increase in the pressure drop and a 1.8-fold increase in the interstitial heat transfer coefficient. Flow visualization indicated that the penetration cooling length is influenced by flow leakage from the porous-fluid interface. Results show at small blockage ratios and low Reynolds numbers, a significant portion of the flow from the porous region leaves it to the clear region on top of the porous block. While, at high Reynolds numbers and large blockage ratios, the flow leakage is reduced. Additionally, for a low blockage ratio (BR < 0.5), the amount of flow leakage depends on the Reynolds number, while it is independent of the Reynolds number for BR > 0.8. Finally, this study introduces a novel correlation for the interstitial heat transfer coefficient derived from conjugate heat transfer pore-scale simulations. The correlation is established on the basis of Reynolds number, blockage ratio, and development length of the metal foam, offering valuable insights into heat transfer phenomena in porous media.