Flux+Temperature on a wall ?

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 August 11, 2006, 05:48 Flux+Temperature on a wall ? #1 tanphi Guest   Posts: n/a Hello, I have a question : does anobody know if it's possible to have as boundary condition for a wall both temperature and heat flux ? (For example : a wall at 100°C with a heat flux of 500W/m² on it) Thank you !

 August 11, 2006, 08:28 Re: Flux+Temperature on a wall ? #2 Raj Kiran Grandhi Guest   Posts: n/a Hello, I guess that would be too many constraints at the boundary. It is like trying to specify the temperature, pressure and density of a gas at the same time. The moment you fix any two properties, the third is automatically fixed by the ideal gas equation. Likewise, for a given flow system, the moment you fix the wall temperature, the heat flux is fixed. Or if you specify the heat-flux, then the wall temperature becomes a derived quantity. What is the physics behind what you are trying to simulate? Do you really have such a situation? HTH, Raj Kiran

 August 11, 2006, 08:46 Re: Flux+Temperature on a wall ? #3 Albert F. Guest   Posts: n/a Hello all, I'm in same situation, I have asked it at fluent support and they have said me that fluent does not support the two conditions. You have to impose one or the other and it is a little bit complicate because when you impose a heat flux you mean that all is radiation but is difficult to impose a quantity for the convection. The surface is also important in this cases because is not the same emiting 2000 W in a small or in a high surface. In fact it is more complicated that seems. I'll try to find out the best choice, I think that there is a tutorial specialized in this terms.

 August 11, 2006, 09:40 Re: Flux+Temperature on a wall ? #4 tanphi Guest   Posts: n/a thank you for your answers Raj, I think you're not right : you can have to specify heat flux and temperature at the same time on a wall, and to have the heat flux does not give automatically the temperature : For example if you want to know the temperature on the other side of the wall, to determine it you must have both temperature and flux. Albert, I think I'll try to make a udf to force fluent to apply both conditions but I don't know if it will work.....

 August 11, 2006, 09:50 Re: Flux+Temperature on a wall ? #5 Albert F. Guest   Posts: n/a Ok tanphi, I'll look for information about this type of boundary conditions but I thing that an UDF would be the right way...

 August 17, 2006, 05:37 Re: Flux+Temperature on a wall ? #6 Albert F. Guest   Posts: n/a Look for this tutorial: Thermal Model of Head Lamps using DO Radiation Model. I think it can help.

 August 19, 2006, 09:06 Re: Flux+Temperature on a wall ? #7 Mark Russell Guest   Posts: n/a Conductive heat flux through the solid is driven by the temperature gradient across it. i.e. Qx = -KA dt/dx. And so the two conditions are intimately connected. Hence I wonder why you feel you need both conditions. Please provide details of the case you are studying.

 August 21, 2006, 02:28 Re: Flux+Temperature on a wall ? #8 Albert F. Guest   Posts: n/a I have a bulb that reamins at 900 ºC at the free stream but also emits 2000 W in radiation terms.

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