CFD simulation of melting process of phase change materials (PCMs) in a spherical capsule

•The effect of container's surface temperature on melting rate is more than other parameters.•At the beginning of the melting process of PCM, the heat conduction mode is dominant.•Natural convection is the ruling mode at the top half of container.•The molten liquid at the top half of the container is naturally stable.•Liquid layer, which is formed at the bottom of the container is unstable.

The present study is focused on CFD simulation of constrained melting of Phase Change Materials (PCMs) in a spherical container. To investigate the melting process of the PCM, its melting fraction was analyzed at different times. The results indicated the existence of thermally stable layers on the top of the sphere. Moreover, inspection of the calculated temperatures at different points along the vertical axis indicates the existence of some disturbances at the bottom of the sphere due to the natural convection. After the validation of the results, the effects of different parameters such as the surface temperature of the capsule, the initial temperature and the size of the spherical capsules, on the melting process were investigated. The initial temperature did not affect the melting rate, whereas melting rate increased by increasing the surface temperature of the capsule and also decreasing the diameter of the sphere. The results showed that the surface temperature of capsule compared to geometrical parameters and other operational conditions can have a greater influence on the melting rate and the heat flux.