[Oula]

Hi everyone
I'm using a special UDF to monitor the temperature on a wall. So the BC at that wall is unknown I want it as output of the simulation. I only know that at the beginning of simulation its temperature is 293 K and I want fluent to give me a data of temperature vs time of that wall. My questionis, how should I set the BC of the wall in the boundary condition panel?

what I did is setting the operating temperature to 293 K, then in Thermal Conditions> I ticked the Radiation option, I adjust the value of the external emissivity to 0.8. I could not decide about the external radiation temperature. Do I have to leave it as 293 or set it as zero. what do you think?
Any help is much appreciated

[LuckyTran]

Well what is the radiation environment? If you know the external emissivity is 0.8, what is the temperature that corresponds such that the emissivity is 0.8? Did the 0.8 come from a random number generator? How did you decide on 0.8. The answer to the temperature is deeply connected to this 0.8.

[AlexanderZ]

Do you have only radiation, no convection? emission coef depends on the surface type. It is possible to find this value relatively accurate in books.
You may describe the case you want to simulate in more details, so others could help you

best regards

[Oula]

Hi AlexanderZ

The value of 0.8 emissivity I got it from literature. The surface is heated mainly by radiation but I want to promote convection using a specific technique. Therefore the case that I'm working on can be described as a mixture of convection and radiation.