Simulation of liquid–vapour phase change process inside porous media using modified enthalpy formulation

• The existing enthalpy formulation has been critically analysed.
• A modified formulation has been proposed that eliminates the identified drawbacks.
• The formulation is applicable even in presence of substantial density variations.
• One dimensional phase change problem has been considered as demonstrative example.
• Smoothing of effective diffusion coefficient is required for all variants of TPMM.

In the present article, after critically analysing the drawbacks of the existing h-formulation based on Two Phase Mixture Model (TPMM), a modified formulation has been developed that can easily accommodate substantial density variations in the single phase regions. The results for steady one-dimensional complete liquid–vapour phase change problems of water inside a porous evaporator, obtained from the modified h- and the existing H-formulations, have been compared and excellent agreements have been observed for all tested cases. It has been also observed that the modified h-formulation requires significantly less computation time, although all variants of TPMM requires smoothing of effective diffusion coefficient in order to avoid “jumps” in the predicted properties. Since the proposed formulation does not require the definition of any artificial variable and in view of the identified advantages, the method is strongly recommended for the future use. Nevertheless, it should now be extended in order to accommodate the local thermal non-equilibrium condition and multi-dimensional phase change problems in presence of substantial density variations in the single phase regions.