In this case sandwich is made of : sheet metal plate / rockwool / sheet metal plate.
How is this kind of problem solved in cosmosworks or is it impossible to do that

you have to determine the values of heat flux, temperature, heat flow. Thinking about the error's reason, I suppose you did not used either radiation or contact between the surface directly, because in this case thermal solver does nothing about how the heat is being transferred. Check your model or upload it here - we'll have a look.
As I know how one of the surfaces is heated, I of course want to know, how fast the heat is transferred to the other surface of the panel. ..that is: What is the temperature of the other surface after a given time (say 15 minutes).
excuse me,i am new in using thermal analysis of SOLIDWORKS simulation. right now i am doing the same case, thermal analysis on sandwich structure, but with additional gap (with natural air).
if thermal conductivity will transfer the heat for touching face, how to make the heat transferred from one surface to another for simulating the effect of the gap in order to reduce the heat? because the desired outcome is to know the impact the difference distance in gap (not vacuum gap) to minimize the heat.
do i have to design the part and define it as "air" or i have to use radiation "boundary condiiton"? thanks for any advice and help.
Regards
Aufar
I have some experience in that and I think it is not more complicated than the transient analysis on coupled surfaces. So, first make the contact between the coincident surfaces (set the contact meshing node-to-node or similar), define your materials, assign the initial temperature for all your parts, define the temperature change, heat flux and radiation if necessary, and try to run the analysis... Hope the results will satisfy you.
Regards,Basil.