Speaker
Description
Evaporation from a porous medium into a free flow is one of the fundamental processes
in environmental systems (e.g. the evaporation of water from soil into the atmosphere
[1]). In technical systems self-pumping transpiration cooling can be realized with the
help of porous materials where the combination of capillary action and phase change
is a promising approach to cool structures due to its high cooling efficiency [2]. The
distribution of liquid in the porous material, namely the existence of continuous liquid
pathways to the surface of the porous medium influences significantly the evaporation
rate [3]. Furthermore, the condition of the turbulent boundary layer in which the vapor
is transported away from the surface is of great importance.
Hybrid-dimensional models are successfully used for the efficient modeling of
such systems under laminar flow conditions [4]. These models use coupling conditions
to ensure the continuity of mass, momentum and energy between the pore network
model (PNM) and the free-flow domain. But these coupling conditions comprise
unknown parameters (e.g. the slip length) and their validity for turbulent flows is
unclear. One possibility to evaluate the validity of coupling conditions and to derive
closures for the unknown parameters is to fully resolve the Navier–Stokes equations in
the free flow and the pore space.
In this talk results of such pore resolved calculations are presented for a porous
medium with different water saturation levels. The focus will be on the momentum
balance at the interface. It will be discussed (i) how the rough, permeable surface
influences the turbulent boundary layer, (ii) how the fluid distribution will influence
the effective roughness and (iii) how the pore wall wettability influences the fluid
distribution.
Finally a possible approach for a coupling condition for the momentum balance
of a turbulent flow with a porous medium under different saturation levels is presented.
References
References
[1] D. Or, P. Lehmann, E. Shahraeeni, and N. Shokri. Advances in soil evaporation
physics—a review. Vadose Zone Journal, 12(4):1–16, 2013.
[2] G. Huang, Z. Liao, R. Xu, Y. Zhu, and P. Jiang. Self-pumping transpiration cool-
ing with phase change for sintered porous plates. Applied Thermal Engineering,
159:113870, 2019.
[3] VA. Jambhekar, R. Helmig, N. Schröder, and N. Shokri. Free-flow–porous-media
coupling for evaporation-driven transport and precipitation of salt in soil. Transport
in Porous Media, 110(2):251–280, 2015.
[4] K. Weishaupt and R. Helmig. A dynamic and fully implicit non-isothermal, two-
phase, two-component pore-network model coupled to single-phase free flow for
the pore-scale description of evaporation processes. Water Resources Research,
57(4):e2020WR028772, 2021.
| Participation | In-Person |
|---|---|
| Country | Germany |
| MDPI Energies Student Poster Award | No, do not submit my presenation for the student posters award. |
| Acceptance of the Terms & Conditions | Click here to agree |
