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In this work, the feasibility of a phase change material (PCM) thermal storage unit is determined, and the design is then optimized to minimize the time it takes for the PCM to completely melt. The PCM provides a large energy density due to its characteristically large heat of fusion, but has a low thermal conductivity, leading to slow transient responses. Thus, a heatsink is employed to increase the melt rate. The heatsink is analyzed using three different methods to determine which method provides the best results in the least amount of time. First, SolidWorks’ simulation tool with a variable specific heat model is used to perform a thermal finite-element analysis (FEA); second, Fluent is used to perform a computational fluid dynamic (CFD) analysis with the Boussinesq approximation; third, Fluent is used to perform a CFD analysis accounting for the variable specific heat of PCM. The results are compared and used to suggest an analysis technique when working with PCM, as well as the dimensions of a heatsink to be used in thermal storage applications with PCM. A sample solar thermal system is then presented, utilizing the heatsink that was developed. Ultimately, the Fluent CFD analysis, taking into account the variable density of the PCM, was found to provide the best results, but took on average 2.5 days of computational time to solve. The SolidWorks FEA model was found to provide accurate results for conduction dominated cases with the simulation solving in under 30 minutes. It is found that a variable specific heat finite-element model can quickly provide accurate results when analyzing a conduction dominated melting process. |
