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Old   May 13, 2005, 02:59
Default non thermal equilibrium problem
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HI All (especially Jeff, Robin, Hannibal):

I have a quit similar problem that described by Hannibal few years earlier. Link is:

I have read the answer written by Jeff and Robin and its a nice solution but I have some confusion about last part. According to Jeff I have to simulate enthalpy as an aditional variable. Its clear to me but later part is not clear. How heat will be transfered from solid surface to fluid? Its clear that I will get T by enthalpy/Cp at each node but how I will access each node enthalpy value and how I will implement heat transfer equation (q=alpha*A(Tsolid - Tfluid)) at each node.

Please help me at your convenience.

regards... NewInCFX
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Old   May 14, 2005, 16:31
Default Re: non thermal equilibrium problem
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Hi NewInCFX,

If you follow the same approach, then all you have to do is include a subdomain with sources for both your additional varialbe and the fluid's energy equation. You can simply define your expression for q, then specify the sources as q and -q respectively.

Regards, Robin
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Old   May 15, 2005, 04:43
Default Re: non thermal equilibrium problem
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Your equation it correct. (q=alpha*A(Tsolid - Tfluid)) You need, in CEL, to set your heat transfer coefficient (alpha), calculate A (based on porosty), get Tsolid from (H_user/Cp_solid), and Tfluid is already provided. Then as Robin says, set your q and -q in the energy equation and the "extra" solid enthalpy scalar using your equation in the subdomain that includes the porous media.

Note: I have not done this in CFX-5 yet, only in CFX-4. But I believe all the components are there at this point.
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Old   May 17, 2005, 10:44
Default Re: non thermal equilibrium problem
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Hi Jeff and Robin:

Thanks a lot for your help. Its now quit clear but I have few confusion and For that I am writting again.

1. Problem is to determining the heattransfer area A (based on porosity). In my case the bed is packed with spherical ball and I don't know the mess size and how many ball lies in one mess. One thing I could do that I could calculate effective total cross section area like: (effective area Aeff = total CrossSection A * Porosity) or Should I use function area()@inflow * Porosity.

2. I guess by H_user you mean the enthalpy that was simulated as an aditional variable, am I right?

Thanks a lot

regards... NewInCFX
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