Simulation of natural convection and radiation of a radiant heater in a room
 

Hi
I am desperately trying to simulate heating of a 2D room by a radiant heater which is suspended from the ceiling. Heater has two radiant tubes on which I define a specific temperature. And I also define mixed thermal boundary condition for the walls (radiation and convection with surrounding). I am using ideal gas modeling for air because the temperature gradient in the room is high. Below is my problem setup in Fluent 16.2:

steady state
Ideal gas
DO for radiation: I am using 100 for angular discretization
Turbulent modeling: K-omega sst, k-epsilon realizable (I tried both with different near wall resolution) (Used Standard wall fcn and enhanced wall fcn)
Solution method: Coupled (when I change scheme to SIMPLE or PISO it diverged)
Pressure: Body force weighted
Second order upwind for other variables
I use Pseudo transient method
Operating condition: 101325 Pa, 273.15 K, density=0
T_left_tube=500 k, T_right_tube= 400 k, surrounding temperature is 273 k

The residuals wont go down below 10^-3 and they oscillate. And I also run the case for laminar flow but the residuals didn't converge. I attached the domain geometry, the mesh, and residual curve.





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