Here are two plots : one with Nodes values on and other with node values off.
They show different values. High temperature at the solid-fluid interface is very high when using node values.
What causes this difference?
The radiation flux has realistic values. (matching with analytical values)
Yes, radiation travels very quickly. But, solids cannot get hot with such unrealistic rate.
As I am writing report file of average temperature at the interface and it uses node values it shows the jump. Is there any way to use cell values in report?