# Phase change phenomena in Fluent v15

• Imane

#### Imane

Hello everyone,
I am beginner in fluent v15, and I want to simulate the temperature change as a function of time in the phase change materials "PCM" and the heat thermal fluid "HTF" and the PCM fusion Front.
Regarding the geometry I chose to work with two coaxial tubes: the inner tube contains the heat thermal fluid and the outer tube contains the PCM
for meshing I appointed the input, output and symmetry area of HTF and PCM. Also the entry, exit and the symmetry of the wall between the PCM and the HTF
The set up steps followed are:
General ==> Type: based pressure, velocity formulation: absolute, time: transient
Model ==> volume of fluid with 2 stages in number eulerian, energy, melting and solidification
Materials ==> PCM characteristics: density, solidius and liquidus temperature , thermal conductivity, pure solvent latent heat and thermal expansion coefficient
for the HTF I chose to work with liquid water
Phases ==> Primary phase pcm, Secondary phase HTF
Cell Condition box ==> Wall (phase mixture, Type: Solid)
HTF (phase mixture type: Fluid, Fluid porosity: 1)
PCM (phase mixture type: Fluid, Fluid porosity: 1)
NB: I want to determine the porosity of the fluid depending on the temperature f (T)
- f(T) = 0 if T < Ts
- f(T) = 1 if T > Tm
- 0 < f(T) = (T -Ts) / (Tm - Ts ) < 1 if Ts < T < Tm
but I don't know how to do it with new input parameter
Boundary Conditions ==> in this stage I entered the HTF input velocity and the inlet and outlet temperatures of the HTF, PCM and WALL but I find myself stuck facing problem with the symmetry area of HTF and PCM.
and other boundary conditions appear as: wall-htf-wall, wall-htf-shadow-wall, wall-pcm, wall-pcm-wall, wall-pcm shadow-wall, wall-wall
but I do not know what to choose for thermal conditions: temperature convection heat flow or or ...
and if for example I chose the heat flux how can I calculate the heat generation rate and the heat flux.

I will be very grateful for your help and thank you in advance.

Best regards;

For the boundary conditions, you need to decide what type of thermal conditions you want to apply. If you want to use convection heat transfer, then you should select "Convective Heat Flux" as the boundary condition type. You can then enter the convective heat transfer coefficient and the ambient temperature, which are usually given in the problem statement or can be estimated using correlations.If you want to use a heat flux, then you should select "Heat Flux" as the boundary condition type. You can then enter the heat flux, which is usually given in the problem statement or can be estimated using correlations.Once you have selected the boundary condition type, it is important to make sure that the boundary condition is applied correctly. For example, if the boundary condition is applied to the wall, then the heat flux should be specified in the direction normal to the wall. Similarly, if the boundary condition is applied to the HTF or PCM, then the heat flux should be specified in the direction normal to the surface of the HTF or PCM.Finally, you also need to specify the heat generation rate. This is usually given in the problem statement or can be estimated using correlations.I hope this helps!