Numerical Investigation of the Effect of the Mushy Zone Parameter and the Thermal Properties of Paraffin-Based PCMs on Solidification Modeling Under T-History Conditions

Abstract

Phase change materials (PCMs) are widely used in various critical applications because of their capacity to store thermal energy and regulate temperature effectively. A review of the literature on PCM solidification and melting simulations reveals that the accuracy of these simulations is highly dependent on the input parameters and underlying assumptions used in the software. Among the key factors influencing precise simulation results are the parameter of mushy zone ($A_{\text{mushy}}$) and the thermal properties of the material. This study numerically investigated the impact of the $A_{\text{mushy}}$ and thermal properties on the solidification behavior of a paraffin in the test tube under T-history conditions. The analysis was conducted using the commercial CFD software ANSYS Fluent and the enthalpy-porosity method is applied to simulation the solidification process. To accurately reflect the conditions of the T-history experiment, radiative heat transfer between surfaces was employed for the boundary conditions, ensuring a realistic representation of the experimental setup. An evaluation of four thermal properties—thermal conductivity, density, latent heat, and specific heat—indicates that while an increase in latent heat, density, and specific heat slows down the rate of solidification, an increase in thermal conductivity has the opposite effect, accelerating the solidification process. The results further emphasize that selecting an appropriate value for $A_{\text{mushy}}$ is crucial for achieving accurate solidification simulations. Increasing $A_{\text{mushy}}$ from ${10}^5$ to ${10}^8$ enhanced the prediction accuracy of the solidification time by 10%. Additionally, the mushy zone parameter significantly affects the shape and progression of solidification. As $A_{\text{mushy}}$ increases, solidification in the lower layers decreases, concentrating the process more in the layers adjacent to the cold wall.