Dear Chhabishwar Prasad Patel

Very fine mesh, heavy boundary condition and physics, small time step and maybe the low power of the processor are reasons of this problem.

If your model is symmetric, you can simulate one side of model and use from symmetry option in physics.

Hi,

Can you give more details on your model, is it a 3D and how you set up PCM properties.

1. Very fine mesh

2. Small time step

These are the two probable reasons.

You can use comsol's pipeflow library, it simplifies the model and give you reasonable results

Hi,

If the issue is that simulation took long time! I would suggest three things:

1-If your model is a 3D and you have a single pipe or a number of pipes, you can scale down the fine mesh in the longitudinal direction (flow direction) to 0.5 since the temperature and velocity gradients are dominant in radial direction. This can be found under mesh node then 'free Tetrahedral' then 'Scale geometry'.

2- Make sure that the boundary conditions are consistent since you are performing transient simulations. It is recommended to use step function to ramp up velocity and temperature if their values at boundary conditions are different from the initial values.

3- Use the default solver but with appropriate time step (not large and not small).

Hope that helps