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February 2, 2006, 09:22 
constant heat flux boundary condition

#1 
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I am having trouble writing a finite difference scheme for the constant heat flux boundary condition in porous media using the local thermal nonequilibrium model; kf(dT/dy)= ks(dT/dy). In which kf is fluid conductivity and ks is solid. This is the boundary condition at the wall. I think I am confused at what exactly is 'at the wall'. Which leads to the problem I am having of definig the 'dy' term.
thanks 

February 2, 2006, 10:00 
Re: constant heat flux boundary condition

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Hi Andrew,
A thought, The surface heat balance would be, kf(dT/dy)= q',flux where: q',flux is the value of the edge thermal flux you are setting; You can then set up the dT/dy relationship accordingly. I hope this is of use. diaw... 

February 2, 2006, 10:21 
Re: constant heat flux boundary condition

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that is pretty much how I did it. I was just confused at how I could have a 'kf' at the wall if I hadn't even made it to the fluid yet and was still in the wall. What I did for the fluid temperature was use T(x)=Tin + (q"(width)(x)/(mdot*Cp))to find the fluid temperature at 'dy' from the wall. Then, I back track to get the wall temperature. Then, knowing the dT/dy for the fluid is equal to dT/dy for the solid I can get the solid temperatures.
thanks 

February 2, 2006, 11:31 
Re: constant heat flux boundary condition

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Hi Andrew,
You have a surface heatbalance at the boundary. From the solid side, you impose the q',flux = q',in/ dA,surface. The heat entering the surace, from the solid, must exit the surface, into the fluid. This is the kf*dT/dy*dA,surface term. You can then construct the appropriate boundary term into that particular FD element. Have fun. diaw... 

February 19, 2006, 14:54 
Re: constant heat flux boundary condition

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dear sir
i am upender doing mtech in thermal sciences. sir, i would like to know what r the possible methods to maintain constant heat flux in convection over a cylinder. even if we give the constant heat input it is not possible to maintain constant heat flux every where on the cylinder . can u pls send the experimental setup to maintain the same.. waiting for ur reply i will be obliged if u can send that. thanking u sir 

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