Local Thermal Non-equilibrium Models in Porous Media: A Comparative Study Under Forced Convection

Heat transfer in saturated porous media plays a key role in many applications. Under certain conditions, the classical assumption of instantaneous heat transfer between phases may no longer hold, leading to local thermal non-equilibrium (LTNE). Even though many continuum-scale LTNE models exist, systematic comparisons between different models remain limited. In this study, we compare a dual-network model and different LTNE-REV-scale formulations under forced convection to evaluate their consistency in predicting LTNE behavior and to assess the influence of different model formulations. Simulations are performed for both steady-state and transient setups. For each setup and model, temperature profiles and non-dimensional temperature differences are analyzed for varying non-dimensional numbers, including Reynolds number, thermal conductivity ratio and Biot number. Across the investigated regimes, all empirical models predict an increase in LTNE with increasing Reynolds number and decreasing Biot number. However, no consistent trend is observed for varying thermal conductivity ratios. Differences between the models can be addressed to the different formulations of effective thermal properties. For idealized systems under natural porous-media conditions, in particular small Reynolds numbers, similar bulk conductivities and high Biot numbers, all models predict near-zero local fluid–solid temperature differences (LTE behavior). Under other conditions, however, the models differ in the magnitude of local temperature difference they predict, i.e., in the degree of LTNE. This highlights the importance of comparisons against detailed experimental data or simulations, for example, within the framework of a benchmark study. Article Highlights The magnitude of the interfacial exchange term strongly correlates with resulting fluid–solid temperature differences Empirical models show increase in fluid–solid temperature difference for high velocities and low interfacial area For idealized systems under natural porous-media conditions, fluid and solid temperatures equalize almost instantly