In micro-CT images, the solid temperature is usually assumed constant. As a result, all of the studies previously cited only considered a gradient of temperature in the solid during conjugate heat transfer in simplified geometries.
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However this approach has two drawbacks, namely the requirement for an exact correspondence between the fluid and solid boundary cells, and the need to iterate over the full solution scheme to stabilize the coupled boundary conditions between fluid and solid. This method has been employed successfully to model conjugate heat transfer in open-cell solid foam and micro-CT images of rocks. However, the use of pore-scale CFD to investigate conjugate heat transfer is still in its infancy.Ĭonjugate heat transfer is traditionally modelled in CFD using a two-medium approach, in which heat transfer in the fluid and solid are solved separately and then coupled by boundary conditions at the fluid-solid interface. Pore-scale CFD has been successfully applied to investigate hydrodynamic dispersion, multiphase flow, single-phase reactive transport, multiphase reactive transport and electric charge transport. Pore-scale CFD resolves the interface position and concentration gradients exactly, so that the impact of pore-level properties such as surface area, pore-size distribution and contact angle can be investigated and enabling the development of upscaling methods from the micro- to the meso- and the macro-scale. the interconnected void space between the solid grains, offering an unprecedented window into the physics of porous media applications. Applied to 3D X-ray computed micro-tomography images of porous media, flow and transport equations can be solved directly inside the pore-space, i.e. To optimally design for such technologies it is necessary to have a detailed understanding of the transport properties of mass, momentum and energy in porous media at every scale.Ĭomputational Fluid Dynamics (CFD) is an extraordinary tool to design and optimise engineering processes. In addition, the temperature controls processes that may influence the performance of the system, including viscous dissipation, chemical reactions, phase transfer and electrical conductivity. All of these applications include a range of mechanisms that occur at multiple scales as well as heat transfer at the fluid-solid interface. Heat transfer in porous media is of the utmost importance for a range of energy-related applications, including geothermal energy engineering, heat exchangers, nuclear reactors, in-situ combustion and pyrolysis, packed-bed reactors, CO \(_2\) capture and storage, solar cells and battery technology. 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. Our model is validated by comparison with the standard two-medium approach for a simple 2D geometry. 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.
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. GeoChemFoam uses the micro-continuum approach to describe the fluid-solid interface using the volume fraction of fluid and solid in each computational cell. In this paper, we present GeoChemFoam’s novel numerical model for simulation of conjugate heat transfer in micro-CT images of porous media. 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.
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