Abstract
We present a dual network model to simulate coupled single-phase flow and energy transport in porous media including conditions under which local thermal equilibrium cannot be assumed. The models target applications such as the simulation of catalytic reactors, micro-fluidic experiments, or micro-cooling devices. The new technique is based on a recently developed algorithm that extracts both the pore space and the solid grain matrix of a porous medium from CT images into an interconnected network representation. We simulate coupled heat and mass transfer in these networks simultaneously, allowing naturally to model scenarios with heterogeneous temperature distributions in both void space and solid matrix. The model is compared with 3D conjugate heat transfer simulations for both conduction- and convection-dominated scenarios. It is shown to reproduce effective thermal conductivities over a wide range of fluid to solid thermal conductivity ratios with a single parameter set. Morevoer, it captures local thermal nonequilibrium effects in a micro-cooling device scenario.
Highlights
Heat transfer processes and non-isothermal effects are found in many technical and environmental porous-media systems
We introduce a fully coupled, locally energy- and mass-conservative dual network model for the simulation of heat transfer in realistic natural porous media, allowing the consideration of pore-local thermal nonequilibrium and structural heterogeneity
The dual network model has been implemented in the open-source numerical software framework DuMux (Koch et al 2020) which already contains a variety of pore-network model implementations in a development version (Weishaupt et al 2019; Weishaupt 2020)
Summary
Heat transfer processes and non-isothermal effects are found in many technical and environmental porous-media systems. A more sophisticated concept involves solving two separate energy balance equations for the fluid and the solid phase (Satik and Yortsos 1996) Both phases are represented by two individual networks and advective heat fluxes within the fluid phase are considered. In Khan et al (2019), the authors showed that the algorithm can reliably extract void-solid interfacial areas They simulated stationary diffusion separately on both void and solid networks. We introduce a fully coupled, locally energy- and mass-conservative dual network model for the simulation of heat transfer in realistic natural porous media, allowing the consideration of pore-local thermal nonequilibrium and structural heterogeneity. Both subdomains are simplified using the same model reduction technique commonly applied exclusively to the void space, where it is known as pore-network modelling (Table 1)
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