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[1805611570]

Question About Mass Transfer Models for Solid–Liquid Phase Change in CFX 2019 R2

Dear everyone,

I am currently using ANSYS CFX 2019 R2 to simulate a solid–liquid phase change process, in which Solid A (treated as Liquid A) melts into Liquid B.

Since CFX does not have a built-in solid–liquid phase change model, we are considering treating Solid A as a fluid (Liquid A). The viscosity of Liquid A is defined as very high at low temperatures and decreases significantly as the temperature increases, so that its behavior approximates that of a solid at low temperatures and a liquid at high temperatures.

At the initial time, the computational domain contains both Solid A (treated as Liquid A) and Liquid B. We place both phases in the same fluid domain, as shown in Figure 1.

The initial volume fractions are defined according to the spatial distribution shown in Figure 2.

Our main question is about the mass transfer model between the two phases. As shown in Figure 3, CFX provides options such as Phase Change and Specified Mass Transfer.

For this type of solid–liquid phase change, where Solid A (treated as Liquid A) gradually melts into Liquid B as the temperature increases:

1. Which mass transfer model should we use: Phase Change or Specified Mass Transfer?

2. Which model is more appropriate for representing the melting process?

3. If Specified Mass Transfer is recommended, how should the mass transfer rate be defined as a function of temperature or liquid fraction?

4. Are there any other settings or considerations that should be taken into account when implementing this phase change model in CFX 2019 R2?

Any advice or suggestions would be greatly appreciated.

Thank you very much for your help!

 

 

[Rob]

The image upload is a little hit and miss at present - we're working on that. 

CFX doesn't have a solidification model, but Fluent does. I suggest looking at that, and then either use Fluent or use Fluent's approach in CFX. 

[1805611570]

Hello, I am not entirely clear about your suggestion. Could you clarify what I should examine first? Also, what is referred to as the "Fluent‑style method inside CFX"?

[Rob]

Fluent has a solidification-melting model already built in. I suggest you either try in Fluent or use the methodology that Fluent uses (covered in the manual) to write your function for CFX.