temperature change + steady state
 

Hi,

Hope you can help, if I set the wall temperatures of a furnace in the boundary conditions for a steady state problem can these temperatures change with the solution or will they stay at the prescribed temperatures? Please help!!

John

Re: temperature change + steady state
 

John,

If you set the B.C. for the wall as a temperature, it will remain constant at all times. The fluid adjacent to the wall will obviously change as fluid properties permit.

-Eric R.

Re: temperature change + steady state
 

Thanks for your reply Eric,

I want to determine the heat transfer from a flame to the wall when the furnace is running at steady state conditions. So what conditions would I set at the wall so that it's temperature is not higher than the flame temperature and not too low, that it would be creating a bigger gradient than there actually is?

Your help is greatly appreciated.

John

Re: temperature change + steady state
 

John,

I would assume that you are NOT looking for conduction within the wall? Because, theoretically, the surface of the wall (touching the flame) would be at the flame temperature.

If you're not concerned with conduction through the wall, what I think you can do is assign a zero heat flux (0.0 W/M^2-K) to that wall (2-dimensional surface). This way, you're assuming that you'll lose no heat through the wall (perfectly insulated) and that the wall temperature will change with the local flame temperature.

This should be the case b/c I model heat transfer in mixing tanks w/ helical coils and I assume a zero heat flux at the walls, but the walls themselves would have a temperature.

Hope this helps.

-Eric R.

Re: temperature change + steady state
 

Eric,

That was the answer I was looking for, Thanks.

As a matter of interest, I wasn't sure if conduction through the wall could be done? If I wanted to determine that, I guess I would just change the heat flux b/c??

Regards, John

Re: temperature change + steady state
 

John,

Actually, if you want to model conduction through the wall, you would have to create the actual wall volume (ie. give the walls thickness). This would have to be meshed also. This volume would be a "solid volume" as defined in Gambit/Fluent, whereas your air/flame/etc. would be a "fluid volume."

There's some option about "thickness" in the thermal conditions for a wall, but I don't exactly what this is and if it's related to conduction... Good luck!

-Eric R.