Karthik R

If I understand your issue, the PCM walls are made out of solid 'Steel' and the fluid inside these walls is 'PCM'. Is you want to apply these material properties, then you will need to have a solid outer body (which is your solid pipe with its thickness) and this will be your 'Steel' region. The fluid inside the inner diameter of the pipe will be your PCM region. Right now, it seems like you only have the inner Fluid 'PCM' region in your domain. If you have the outer solid pipe, please create another named selection in Ansys meshing called 'Steel' and you should be seeing it in Fluent under 'Cell Zone Conditions'.

Thank you.