I recreated the case from the beginning by removing the solid-pp.unten/.oben and using the shell conduction instead of separate parts in the simulation model. the simulation worked and heat were transfered through both wall.

am I doing this correctly (shell conduction)?

another thing is, when I simulated the solidification process for 10 hours, I got this liquid fraction (see below), which I think doesn't make any sense for sudden increase in liquid fraction. Am I correct?

liquid fraction for 10 h with time step of 30 min


and when I run it with 1 hour time step and for 5 hours, the pcm is fully melted after 4 hours which contradicts with the plot above. what did i do wrong here?