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Twiti March 26, 2006 21:41

Heat transfer within Porous Media
 
Is that possible to accout for both flow and heat transfer in porous media? I have checked the ANSYS CFX manual and found that the energy equation only take the consideration of fluid (section: ANSYS CFX-Solver, Release 10.0: Theory | Basic Solver Capability Theory | Flow in Porous Media | ). I wonder how can I add the heat transfer from solid framework to fluid flow under the assumption of either thermal equilibrium or non thermal equilibrium.

Opaque March 26, 2006 23:55

Re: Heat transfer within Porous Media
 
Dear Twiti,

If you want to do the thermal equilibrium approximation, that is T_solid = T_fluid, you can "fake" the thermal conductivity within the porous domain as

K = (K_fluid * Volume Porosity + K_solid * (1-Volume Porosity)) / Volume Porosity..

That should work..

For the non-thermal equilibrium, the workaround is more elaborate (via additional variables), and you should contact your CFX help desk for details..

Good luck, Opaque..


Eugeny Pavlov March 27, 2006 02:24

Re: Heat transfer within Porous Media
 
Yes, this is problem of CFX. I ask my frend in Moskow, and they reply to my -"It is impossible, becouse no contact access to nodal value of function". In STAR-CD this is possible.

Sorry for my english Russia, Syberia, Krasnoyarsk

opaque March 27, 2006 10:08

Re: Heat transfer within Porous Media
 
Dear Eugeny,

If your friend is interested in solving a similar problem as Twiti, and has ANSYS CFX 10.0 already, sugggest to contact the CFX help desk.. Help desk can give them a note describing how to solve this issue using Additional Variables.. Requires a bit of a variable substitution for the equations to introduce the solid properties in a fluid equation..

It has been done for steady and transient problems.. You just need to know what the ANSYS CFX solver is doing, to workaround the current limitations.. There is no need to access internal data..

Good luck, Opaque

martin March 28, 2006 15:23

Re: Heat transfer within Porous Media
 
the solution is "Diffusive Transport Model" This equation does not compute the convective part. So the quantity is only transported by diffusion and will stay in place.

that's the way I've done:

Add some additional variable(unspecified): cpSolid rhoSolid VSolid ASolid mSolid TSolid kSolid

and AV specific: HSolid

In Fluid Model you can define the values for individual AV eg. (all algrebaic eq): cpSolid=500[W/(m^2*K)] rhoSolid=200[kg/m^3] VSolid=0.1*Volume of Finite Volumes ASolid=200[m^2/m^3]*Volume of Finite Volumes mSolid=VSolid*rhoSolid TSolid=HSolid/(mSolid*cpSolid) cpSolid=1000[J/(kg*K)]

and HSolid as Transport Equation. Kinematic Diffusity is the thermal diffusivity. But as you just want to have it in your subdomain you should define: 2e-4[m^2/s]*Subdomain, so outside the subdomain it is 0.0.

You can't define Diffusive Transport in Pre, so define normal transport and edit the def-file later.

the sources in your subdomain are: for the fluid kSolid*ASolid*(TSolid-Temperature)/Volume of Finite Volumes for the solid kSolid*ASolid*(Temperature-TSolid)* Density

If you expect great gradients it is good to define source coefficients.

that's it. bye martin

opaque March 28, 2006 15:38

Re: Heat transfer within Porous Media
 
Dear Martin,

Thanks for the hints, but this applies to the porous domain approximation via Fluid Domain plus a SubDomain.. I think that Twiti wants to use the Porous Domain as in 10.0 (this is a new feature)..

Your approximation does not account for the fact that the solid matrix has a different volume than the fluid part.. Here , the solid and fluid are within the same porous domain. However, the idea is very similar but you must include the Volume Porosity in your terms..

Twiti, you can also pick it up from here.. Good luck, Opaque

JOGENDRA PAL November 7, 2015 10:29

dear all.. i am facing same problem. can u please tell me how to simulate convection effect of fluid in porous media


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