Modelling of Convective Heat Transfer in Porous Media

This thesis details the process taken for the computational modelling of convective heat transfer in porous media with the objective of improving the accuracy of porous continuum models. CFD simulations were performed to predict convective heat transfer resulting from forced flow through highly conductive porous blocks. For the pore-level predictions, an idealized geometric model for spherical-void-phase porous materials was used to generate several domains over a range of porosity and pore diameter typical of graphitic foams. Simulation on these domains was conducted using the commercial software ANSYS CFX. Similar simulations were conducted using an in-house conjugate domain solver wherein porous regions are modelled using a porous continuum approach. These results were compared to the pore-level results and indicate that a modification to the conductivity of the solid phase of the porous material must be included to account for the tortuosity, or complexity of the solid structure. The tortuosity is shown to appear naturally in the derivation of the volume-averaged energy equation for the solid-phase constituent, and has not previously been considered when calculating the effective solid phase conductivity. The implementation of this modification resulted in a closer match of the heat transfer predicted by the in-house porous continuum model when compared to results generated by commercial CFD software. Subsequent simulations were performed to show that the tortuosity was purely a geometric function – depending only on the solid phase structure.