Learning Forum

[Rugaard]

Hello everyone !

I am working on the simulation of the melting of a phase change material, a paraffin wax named RT40. I want to visualize the phase change on a time-temperature diagram with ANSYS-FLUENT.

Initialy the RT40 is set to 293 K, the cylinder to 323 K. (Phase change is around 311 and 316 K)

I created on ANSYS-ICEM a cylinder closed on both side as the picture below :

As far as i know my mesh is fine, my criteria were :

• Angle > 18 °


• Quality > 0.3


• Aspect Ratio <1000


• Determinant >0.3


• Volume change <10


• Erikson skewness >0.8

Tell me if something is wrong with these criteria.

On Ansys-Fluent, i turned on the "energy" model and the "solidification and melting" model.

I created a material named rt40 with the following properties :

For the density, the specific heat capacity and the thermal conductivity i choose a piecewise-linear model with 4 points (273 - 311 - 316 - 373 K for the temperature) :

I fixed the temperature value of the cylinder to 323 K :

For boundaries between PCM and the cylinder, "coupled" was chosen : (The picture only show the bottom boundary)

For boundaries between the cylinder and the exterior, i just made them adiabatic :

The following pictures shows the methods and controls used :

Then i initialized and patched the PCM zone to 293 K , the cylinder zone to 323 K.

I created 3 points in the center of the cylinder to visualize when my melting is over and the phase change plateau.

The following picture shows my parameters for the calculation :

The residuals are set to 1e-6, i choose 1000 for "Max iterations/Time set" to ensure that the beginning of the calculation converge.

Now my problem is this :

This is a plot of the temperature of a point in the middle of the cylinder. But we can't see a plateau where the phase change appears.

Where is/are my errors ?

 

Best regards

[Rob]

Post a few images of temperature on a plane. 

[Rugaard]

Hello rwoolhou and thank you for reading me.
Here some pictures :

The first one was at 800 time steps, then 1600, 2400 and 3200.

Thank you