Learning Forum

[Alwan Hibatullah]

Is there a difference in how to simulate the fluent for the fluid domain which is given constant heat flux on the wall and with the fluid domain which is exposed to heat from the solid domain which is given constant heat flux?

because when I do a simulation in the fluid domain that is given a constant heat flux with a simulation of heat transfer from solid to fluid, it has a different temperature value on the fluid wall. even though the heat flux for both is the same

 

[Rob]

It's down to the solid properties: in the case with the solid the flux heats & conducts through the solid to the fluid. In the other case the flux is added straight to the fluid. The third option you didn't mention is adding a thickness to the thin wall surrounding the fluid (open up the wall boundary panel in Fluent) to see. 

[Alwan Hibatullah]

In the case of heat flowing from a solid to a fluid, what must be considered so that the results can be the same as when the heat flux is added directly to the fluid?

[Rob]

Usually the solid thickness. Have a look at the thermal lectures in Learning and some of the tutorial in Fluent's Help system. 

[Alwan Hibatullah]

so for a solid wall that is given heat flux, the thickness must also be given according to the boundary conditions?

[Rob]

If you want to account for the solid conductivity etc, yes. 

[Alwan Hibatullah]

But, if we focus on heat transfer, is that necessary? because as I said, there is a difference in temperature value between the heat flux that propagates from the solid to the fluid and the heat flux that is applied directly to the fluid

I'm still confused there, as if when heat propagates from solid to fluid, the temperature on the walls of the fluid becomes stuck and cannot flow properly even though the temperature at the outlet is appropriate.

[Rob]

A heat flux needs a temperature difference to work. But, if the "cold" side can't take the heat the "hot" side will increase in temperature until it can.