Radiation
 

Dear topsedar, I am simulating the same case and i don't know how to design the vacuum between two solids where only heat radiation occurs. Did you assume it is as solid and what are the material properties? or is there another way to setup the vacuum? I really appreciate your help. Thank you.

My posts tell you exactly how to do it. Model it as a transparent solid with an almost zero thermal conductivity.

Dear ghorrocks, how can i make the solid transparent and what are the suggested values of the solid material properties as shown in the attachment. I appreciate your help and thank you

The tab you are showing is for a fluid. You need to make it a solid.

In the radiation properties make absorption coeff=0. Now it does not absorb, that is it is transparent.

This photo is for the material properties which its thermodynamic state is chosen to be solid. It solid domain will be chosen when applying boundary condition as shown in the attached photo "CFD2.jpg". If I am still doing it wrong please tell me what is the correct way. Otherwise will you please give me the best properties approximation that represents the vacuum material as shown in the first attached "CFD.jpg". In term of "Molar mass, Density, Specific heay capacity, Ref. Spec. Enthalpy, Entropy, Dynamic Viscosity, Thermal Conductivity, Refractive Index, Absorption Coefficient, Scattering Coefficient, Thermal Expansivity"

Will you please look into my question? The submission is soon and I need to be done with it. Thank you

Almost all of those parameters are irrelevant. Some require values just to keep the solver happy. I will leave it as an exercise for you to work this out. If you are not sure whether a parameter is important or not then do a sensitivity check (run a value then 10x the value and see if it makes a difference) to find out.

And just a comment - do not rush people on a free open forum like this. If you are in a hurry you should pay for support from ANSYS. On a free forum you get help when we get around to it.

Radiation in fluent
 

Topsedar, can you help me how you resolve this problem. I am using fluent in the same case with your's and I find it very difficult to simulate Annulus using radiation (surface to surface) and also want to know if I can consider the vacuum space as solid or fluid.

Setting up radiation is very different between CFX and Fluent. So if you want help on radiation modelling in Fluent then post on the Fluent forum.