Speaker
Description
Local thermal equilibrium, meaning an instantaneous heat transfer between different phases, is often assumed when modeling heat transfer in porous media systems. However, for some technical applications as well as environmental systems, such as self-pumping transpiration cooling [2], fuel cells [4] and geothermal systems [3], heat exchange processes between the different phases may be of great importance e.g. due to large temperature gradients or large differences in thermal properties of the respective phases. Therefore, when modelling those processes, local thermal non-equilibrium (LTNE) processes should be considered to evaluate the validity of the instantaneous heat transfer assumption.
In our presentation, we show a comparative study for conduction as well as conduction and convection processes between three different LTNE-models focusing on the influence of the interface between a solid and a single fluid phase. On the one hand, the pore-scale geometry including the solid-fluid interface will be resolved by the grid and the respective equations are solved for each phase and coupled through interface conditions. On the other hand, two additional models leading to averaged physical properties, such as the temperature, are taken into consideration. The dual network model ([5]) hereby takes the pore geometry still into account by approximating it with ideal shapes, while a model on the Representative Elementary Volume (REV) scale ([6]) accounts for the pore-scale geometry through averaged quantities. For the latter, different effective conductivity approaches (e.g. obtained through homogenization [1]) are considered, indicating the importance of the respective choice. Additionally, we will provide a short outlook on recent ongoing model developments regarding interfacial heat transfer, including a coupled porous-media free-flow model for local thermal non-equilibrium processes.
| References | [1] J.-L. Auriault, C. Boutin, and C.Geindreau. Homogenization of coupled phenomena in heterogenous media. Vol. 149. John Wiley & Sons, 2010. [2] W. Dahmen et al. “Numerical simulation of transpiration cooling through porous material”. In: International journal for numerical methods in fluids 76.6 (2014), pp. 331–365. doi: https://doi.org/10.1002/fld. 3935. url: https://onlinelibrary.wiley.com/doi/10.1002/fld.3935. [3] S. Hamidi et al. “Critical review of the local thermal equilibrium assumption in heterogeneous porous media: Dependence on permeability and porosity contrasts”. In: Applied Thermal Engineering 147 (2019), pp. 962– 971. doi: https://doi.org/10.1016/j.applthermaleng.2018.10.130. url: https://www.sciencedirect.com/science/article/pii/S1359431118345629. [4] J. J. Hwang and P.Y. Chen. “Heat/mass transfer in porous elec- trodes of fuel cells”. In: International Journal of Heat and Mass Transfer 49.13 (2006), pp. 2315–2327. issn: 0017-9310. doi: https://doi.org/10.1016/j.ijheatmasstransfer.2005.11.021. url: https://www.sciencedirect.com/science/article/pii/S0017931006000056. [5] T. Koch et al. “A (Dual) Network Model for Heat Transfer in Porous Media: Toward Efficient Model Concepts for Coupled Systems from Fuel Cells to Heat Exchangers”. In: Transport in Porous Media 140.1 (Oct. 2021), pp. 107–141. issn: 0169-3913, 1573-1634. doi: 10.1007/s11242-021-01602-5. url: https://link.springer.com/10.1007/s11242-021-01602-5. [6] P. Nuske et al. “Modeling two-phase flow in a micro-model with lo- cal thermal non-equilibrium on the Darcy scale”. In: International Journal of Heat and Mass Transfer 88 (2015), pp. 822–835. issn: 0017-9310. doi: https://doi.org/10.1016/j.ijheatmasstransfer.2015.04.057. url: https://www.sciencedirect.com/science/article/pii/ S0017931015004275. |
|---|---|
| Country | Germany |
| Acceptance of the Terms & Conditions | Click here to agree |
