Radiation in PDE thermal model

Dear community,

I am using the PDE toolkit to build a simple transient thermal model. Radiative heat transfer is a weak, yet present contribution to the phenomenon as the object's temperature is max 10°C over ambient temperature and min -8°C (approximately, due to internal heat generation/absorption), the emissivity is 0.3 and the exposition lasts about 10s per step.

The results I get by considering only convection well match experimental data (see attached picture).

When I introduce the radiant contribution, I get a substantial deviation as if the radiant heat transfer between the object and the ambience would increase the object's temperature rather than decrease it.

This makes no physical sense.

Could you please advice if there is a mistake in my code (see below)?

Tamb=298.15;

emiss=0.3;

hCoeff=30;

ta=Tamb-273.15; %in Celsius

thermalBC(thermalmodel,'Face',[1,2,4,6],'ConvectionCoefficient',hCoeff,'AmbientTemperature',ta);

thermalmodel.StefanBoltzmannConstant = 5.670373E-8;

thermalBC(thermalmodel,'Face',[1,2,4,6],'Emissivity',@(region,state) emiss,'AmbientTemperature',ta)

Thank you,

[Tom Kirsch]

Giulia Ulpiani,

Would you be so kind as to share your code for this question and solution? I am trying to become more familiar and skilled with the PDE toolbox, but I am having some issues.

Thank You,

Answer 1

[Ravi Kumar]

To activate both radiation and convection on the same boundary, combine them into one assignment as:

thermalBC(thermalmodel,'Face',[1,2,4,6],'ConvectionCoefficient',hCoeff,'Emissivity',@(region,state) emiss, 'AmbientTemperature',ta);

[Giulia Ulpiani]

Thank you very much. That solved everything.