Numerical investigations on transport properties for SCO2 flow in Gyroid structures with the pore-scale method

Abstract

Supercritical CO₂ (SCO₂) has emerged as a promising coolant for transpiration cooling in combustion chamber liners. The cooling performance is strongly influenced by the transport properties of SCO₂ within porous media. However, the absence of accurate porosity-dependent correlations for customized porous structures has hindered the application of volume-averaged models, which are more appropriate for transpiration design. In this study, Gyroid porous structures with porosities ranging from 30 % to 42 % were reconstructed at the pore scale. Numerical simulations of heat and mass transfer were conducted to investigate the local transport behaviors of SCO₂. Porosity-dependent correlations for permeability, Forchheimer coefficient, convective heat transfer, and effective thermal conductivity were derived from the pore-scale simulation data. The permeability increased exponentially with porosity, while the Forchheimer coefficient decreased linearly from approximately 6.7171 × 10⁴ m⁻¹ to 3.4923 × 10³ m⁻¹ . The effective thermal conductivity was found to require correction factors between 0.57 and 0.78. An empirical correlation for the surface-averaged Nusselt number (Nu_sf) was also proposed, incorporating correction terms to account for temperature-dependent thermophysical properties. These correlations were implemented into a volume-averaged model and validated through conjugate simulations. Comparisons with pore-scale results demonstrated that the LTNE-based volume-averaged model accurately predicts both temperature and velocity fields. Overall, this study presents a multiscale modeling framework for SCO₂ transport in Gyroid porous media and validated empirical correlations, addressing a critical gap in transpiration cooling design using the volume-averaged method.