How can I make the solid PCM to sink to the bottom as it melts?
 

Hi all, I have an enclosure spherical glass that is contain with phase change material (PCM) that is in its solid state initially. Heat will be applied above the melting temperature of the PCM around the spherical glass. During the melting process of the PCM there will be 2 phases present in the enclosure, the liquid and solid state. The solid PCM will drop to the bottom due to the gravitation force.

A 2d mesh was created and exported out from Gambit.

In Fluent, I used Solidification and Melting function in my simulation. All Material properties of the PCM and glass have set accordingly. The Gravity was also enable with Y=-9.81 in the Operating Condition and the Variable-Density Parameters was also set to an operating density of PCM, that is 777kg/m^3. The Body force weighted under Discretization in Solution Control was also selected.

After iterating for 200 sec, the values for the Liquid fraction was calculated but the simulation did not show the solid PCM sink to the bottom of the enclosure.

How can I make the solid PCM to sink to the bottom as it melts?

Thanks, Lim

spherical enclosure
 

I have the same problem sometimes.

You can not get the result that the solid phase sink to the bottom. Because the Solidification Model in Fluent introduces an assumption that the solid phase is fixed and can not flow with the liquid phase. In my opinion, maybe you can try to use the VOF model. But the phase change between liquid and solid interface may be new problem you need to solve.

hi.
I think for simulation of melting of spherical body, we should use slurry model (pcm-granular euilerian model) in fluent.
but I don't know the result is true or no!

I believe Fluent solves only constrained melting/solidification. The problem you are trying to solve is unconstrained melting, which is different and needs an additional momentum equation for the solid phase. The gravity vector you enabled is only for the Boussinesq term but not for the solid to sink.

3D solidification
 

Hi,

I am working on a phase change process including natural convection in closed domain. as long as I am dealing with a 2D model, I get reasonable results. but when I switch to a 3D model, I don't have any movement in the interface which means that it doesn't solve the solidification/melting!

Do have any suggestion or comments about this?

Thanks

Hi, can you tell some detail about momentum source to add to ? thx