Discretization of energy equation
 

Hello,

I am working on PCM modeling with natural convection .
Actually I am working on the temperature transforming model (TTM) in the aim to model the melting of PCM with natural convection using MATLAB.

However, I have found a problem to discretize the energy equation (third equation in Navies Stokes equations) by expressing the enthalpy by the TTM using the heat capacity and temperature. should I take the heat capacity C function of time and space or constant? same for source term S?

I will be highly grateful if you can help me to solve this problem, or if you can recommend me with some advises knowing that I am beginner in numerical modelling and CFD .