Fluid flow and heat transfer in heat exchanger

Dear All,

I am solving a conduction- convection heat transfer problem with 2 dimensional in shell and tube heat exchanger.

Problem Description are as:
The size of inner radius of tube is 6mm. and
outer radius of shell size 12mm.
Now from the inner tube heat transfer fluid is flowing with velocity of 15m/s with constant temperature , (say 200°C).
Whereas, in the shell there is solid phase change material with melting temperature of 34°C.

I put all the thermophysical properties of phase change material as well as heat transfer fluid.

And run the simulation for 6h. but results are not obtained?

The following results i want to check: 1) how the heat transfer takes place from heat transfer fluid to phase change material ( i.e. conduction and convection)

2) At what time the convection will start?

3) I am using fluid thermal interaction module of non-isothermal flow. whether it is correct? or I have to used another module.

Please suggest me how to solve the above problem or give me some guidelines so that I can solve the problem.

Thanking you .

Sincerely,
Vinay Patel.