How To ... ANSYS - Blog Tutorials, Tips and Tricks : Wax melting in Ansys Fluent

In today's post, I would like to introduce you to a simple tutorial on the phenomenon of melting material. Our hero will be wax which we will melt with the help of a given heat flux. Of course, in Ansys Fluent we can simulate both melting and solidification.

Melting a wax in Ansys Fluent

We will apply heat flux [W / m2] to the Top surface. The other walls will be perfectly insulated. They will not be affected by any heat transfer effect. We use such a procedure to simplify our analysis. Our model consists of one wax domain. We will not define the share of gas in this melting process (e.g. air).

Named Selection in Ansys Workbench

In our melting analysis, we define three phenomenon solvers. We will turn on the Energy solver (red box) to transport the energy into the volume of the wax domain. Due to the high density of the material, the fluid movement is defined as laminar (blue frame). This will greatly simplify our analysis - it will increase the degree of linearization of the equations. And most importantly, we include the melting and solidification model (black frame). This will cause additional material properties to appear. We will discuss this later in the post.

Solvers which we need to make melting model in Ansys Fluent

After switching on the model from the black frame, three additional material parameters will appear. Pure Solvent Melting Heat is a parameter that determines what heat is released from the material (spontaneously) during the solidification / melting process. Such data can be found in the literature and materials science. Solidus is the limit temperature at which the material begins to solidify. Liquidus is the temperature limit at which the material begins to melt.

Material properties for wax melting in Ansys Fluent

We must define the wax material as a liquid material, because only these types of materials have additional solidification / melting properties when the black frame model is turned on.

Cell zone condition in Ansys Fluent

We put on heat flux of 1200 W / m2 on the TOP wall. It will be our heat source that heats up the wax. As I mentioned before, the rest of the walls are left as they are perfectly insulated.

BC's for wax melting in Ansys Fluent

Leave all calculation solvers at their default positions - for the transient analysis. As for the size of the time step, we set it to 10 s for 160 iterations, i.e. a total time of 1600 s.

Solvers settings and Size of the time step for transient analysis in Ansys Fluent

Below you can see how the wax melts after applying a heat source of 1200 W / m2 to the TOP surface. With the passage of time, the liquid fraction of the wax increases. As for the distribution of fractions, we are dealing with a fairly non-linear phenomenon, the distribution is not proportional looking towards the depth of the material.