Conductivity and permeability of graphite foams: Analytical modelling and pore-scale simulation

Graphite foams with excellent effective thermal conductivity and large surface area have primarily constituted a new area for the emerging fields of energy conversion, conservation, and management, potentially crucial for reaching the goals of carbon neutrality and emission peak. For such energy applications, graphite foam's thermal conductivity and permeability pave the physical foundation for understanding, designing, and operating thermofluidic flows inside the porous medium. However, previous prediction models of conductivity and permeability seldomly considered the effects of random distributions of pore shape and size intrinsically induced during processing of the graphite foam. To rectify this problem, analytical models of permeability and effective thermal conductivity for graphite foam are derived based on fractal theory, being duly accounted for random distributions of pore shape and size. In parallel, pore-scale numerical simulations are carried out, providing cross-validation and shedding light on transport mechanisms at pore level. Analytical model predictions and numerical simulation results are compared with existing experimental data. Results revealed that fractal analytical models accurately predicted the permeability and conductivity of graphite foams in a porosity range from 0.686 to 0.918, with different parent ligament materials and filling fluids (e.g., air and paraffin wax).