  GeoChemFoam is an open-source OpenFOAM-based numerical modelling toolbox that
includes a range of custom packages to solve complex flow processes including
multiphase transport with interface transfer, single-phase flow in multiscale
porous media, and reactive transport with mineral dissolution. In this paper,
we present GeoChemFoam's novel numerical model for simulation of conjugate heat
transfer in micro-CT images of porous media. GeoChemFoam uses the
micro-continuum approach to describe the fluid-solid interface using the volume
fraction of fluid and solid in each computational cell. The velocity field is
solved using Brinkman's equation with permeability calculated using the
Kozeny-Carman equation which results in a near-zero permeability in the solid
phase. Conjugate heat transfer is then solved with heat convection where the
velocity is non-zero, and the thermal conductivity is calculated as the
harmonic average of phase conductivity weighted by the phase volume fraction.
Our model is validated by comparison with the standard two-medium approach for
a simple 2D geometry. We then simulate conjugate heat transfer and calculate
heat transfer coefficients for different flow regimes and injected fluid
analogous to injection into a geothermal reservoir in a micro-CT image of
Bentheimer sandstone and perform a sensitivity analysis in a porous heat
exchanger with a random sphere packing.
