I have a coupled darcy flow and heat transfer in porous media module in COMSOL.
I would like to independently know the temperature of the fluid and temperature of the porous medium separately, however I see only one temperature. Does anyone know how to incorporate 2 temperatures?
The same has been raised in a COMSOL thread also.
http://www.comsol.co.in/community/forums/general/thread/25247/
Dear Hakeem N.,
you can get the model to working using Laminar flow (all are steady state studies) and the Heat Transfer in Liquids physics separately
Dear Prof. Maddali - Could you please elaborate your answer - Thanks for the input
Dear Dr. Hakeem, N.,
Your studies is somewhat similar to quenching, where temperature distribution is an important parameter for both solid medium and liquid medium
This is an application brief describing the concept of Conjugate Heat Transfer, which is important in many industrial processes, such as quenching.
In this brief, they simulate the heat transfer with and without phase transformation to analyze the rate of heat dissipation with respect to the flow conditions of the coolant media. The fluid flow conditions could then be modified to produce a more regular distribution of heat extraction in a 3D quenching model. This allowed them to stipulate quench conditions for maintaining a uniform temperature gradient, resulting in a more homogenous micro-structure within the final component shape, while reducing residual stresses in the component.
I am not familiar with the particular COMSOL module, but usually such formulations for coupled Darcy flow assume that the porous medium and the fluid flowing through it are at the same local temperature. In other words, the fluid and the porous medium are in local thermal equilibrium.
Several engineering research papers address exactly the point of under what conditions thermal equilibrium can be assumed. Here is a simplified version:
There is a characteristic time for the grains or microstructure of the porous medium to change their temperature when their surface temperature is changed, which depends on the grain size and the thermal diffusivity of the solid material. There is also a time for the temperature to change at the surface of the grains, which depends on the size of the grains and the local pore velocity of the fluid. Whether the fluid and solid are in local thermal equilibrium depends on the ratio of these two times.
Given that the question was in 2014, this answer may now be superfluous....
I agree with Prof Dong Chen - you need to have two different heat transport equations, one for the solid phase and one for the fluid phase. This is known as Local Thermal NonEquilibrium (LTNE), and is now well-studied.
As far as I know, unfortunately, no! Comsol needs to solve two-equation model in porous media, which has not been equipped for. You may write your own code (CFD or LBM), or try to treat a simplified version of your problem analytically. There are many ongoing investigations in this regard.
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