Numerical study of the influences of geometry orientation on phase change material's melting process

The acceleration of the melting process of phase change materials caused by buoyancy-driven natural convection has been widely acknowledged, especially for rectangular geometries. This acceleration phenomenon exists in the cases where phase change materials are heated at the bottom boundary or at both upper and bottom boundaries. This article reveals how the melting rate could be affected by changing the orientation of a rectangular phase change material container with a constant temperature boundary. The transient melting processes of lauric acid in a two-dimensional rectangular container with five orientations (theta = 0 degrees, 22.5 degrees, 45 degrees, 67.5 degrees, and 90 degrees) were simulated using the computational fluid dynamics software. The computational fluid dynamics model was validated against available experimental data obtained from published literature. Results show that when the rectangular geometry is rotated from vertical direction (theta = 0 degrees) to horizontal direction (theta = 90 degrees), the total melting time is increased by about five times. For all investigated orientations, the heat transfer rate at the heated boundary is found to first increase at the initial stage (within about 100min) and then decrease during the following melting process. Moreover, the total amount of thermal storage for the horizontally placed case is slightly lower than the other cases.