Investigation of thermal dispersion and intra-pore turbulent heat flux in porous media

Document identifier: oai:DiVA.org:ltu-77217
Access full text here:10.1016/j.ijheatfluidflow.2019.108523
Keyword: Engineering and Technology, Mechanical Engineering, Fluid Mechanics and Acoustics, Teknik och teknologier, Maskinteknik, Strömningsmekanik och akustik, Turbulence, Porous media, LES, Thermal dispersion, Turbulent heat flux, Strömningslära, Fluid Mechanics
Publication year: 2020
Relevant Sustainable Development Goals (SDGs):
SDG 9 Industry, innovation and infrastructureSDG 7 Affordable and clean energy
The SDG label(s) above have been assigned by OSDG.ai

Abstract:

In the present study, the importance of the thermal dispersion and the turbulent heat flux in porous media and their effects on the macroscopic distribution of thermal energy are investigated. To this end, turbulent flow and heat transfer within five unit-cells mimicking porous media are solved using large eddy simulation. It is shown that the thermal dispersion and the turbulent heat flux are negligible as compared to the convection term in the macroscopic energy equation. When further scrutinizing this equation, it is revealed that except for the longitudinal components of the thermal dispersion, the other components of thermal dispersion and turbulent heat flux may be neglected away from the boundaries as compared to the interfacial heat transfer. Visualizations of vortices show that the size of the turbulence structures within the cells is of the same order as the size of the pores; therefore, the turbulent heat flux is limited to the intra-pore level. Finally, a discussion is provided on the accuracy of the gradient type diffusion model commonly used for turbulent heat flux in porous media in the absence of macroscopic turbulence. It is shown that the intra-pore turbulence does not affect the macroscopic transport of thermal energy within the porous media studied.

Authors

Nima Fallahjoybari

Luleå tekniska universitet; Strömningslära och experimentell mekanik
Other publications >>

Staffan Lundström

Luleå tekniska universitet; Strömningslära och experimentell mekanik
Other publications >>

J. Gunnar I. Hellström

Luleå tekniska universitet; Strömningslära och experimentell mekanik
Other publications >>

Record metadata

Click to view metadata