Learning Forum

[ansysuser]

I want to solve a simple radiation problem involving two spheres of equal radius R, whose surfaces are separated by a distance R. I want to solve the problem where one sphere, call it sphere A, has an assigned outgoing flux and the other sphere, call it B, does not. I take it that if I do not assign a flux to sphere B, that it will act as a re-radiator with zero net flux. They both also radiate to ambient at 0 C. The goal is to solve for their final temperatures.nSo I put Radiation condition on the spheres, but I noticed there is an item called Shell Face in the Geometry Scope. The choices are Top, Bottom, or Both. What is the meaning of this? Which face is the Top face on a sphere? If I select Both does that mean the shell is radiating on the inside of itself? Which selection is needed for my particular problem?nAs I hadn't noticed this before, I solved the system with sphere A set to Both and sphere B set to Top, and I got good convergence but the numbers look wrong. For example, with R = 0.1 and the outgoing flux equal to 1667 W/m^2 I got a total flux probe value for A of 600 W/m^2 when I expected to see the 1667 W/m^2 I assigned. I also got a total flux probe value of 3758 W/m^2 for sphere B! The temperature probe of sphere A is 195 C and the temperature probe of sphere B is 16 C. The thermal error probe shows a maximum error of 6e-5.nAny input would be most welcome.nnThank you.

[Ashish Khemka]

nnWhen using the Surface to Surface correlation with shell bodies, the Details view also includes a Shell Face setting that allows you the choice of applying the load to Both faces, to the Top face only, or to the Bottom face only.nnRegards,nAshish Khemkann

[ansysuser]

Thank you Akhemka.nYour answer didn't help, however. I am asking which face is the top face on a sphere? Which face is the bottom face on a sphere? n

[ansysuser]

Any help here? How can I determine which face is the Top face on a spherical shell? n

[peteroznewman]

If you have meshed the geometry, insert into the Solution branch Elemental Triads, then Evaluate All Results. You don't need it solved to do that. The Top face is the +Z axis.nAnother method is to insert a Contact and you can pick the Top or Bottom of a surface. The selected surface lights up in Red or Blue.nn