Numerical study on unsteady heat transfer characteristics of phase change plates optimized by fin structure

Abstract

The energy crisis has heightened the importance of phase change energy storage technology as a key enabler for orderly energy transformation. However, the density variation of phase change materials during phase transition is often overlooked, leading to issues such as reduced heat transfer efficiency and local overheating. In previous studies, the inhibition effect of phase transition stratification has been found as an incidental result of thermal performance studies. There are few studies have systematically analyzed it. Therefore, in this study, the fin structure is studied by numerical simulation to mitigate the resulting stratification phenomenon. The results can reduce the thermal efficiency loss of the phase change plate and the risk of local overheating of the system. Specifically, the inhibitory effects of fin length, the number of transverse fins, and the presence of longitudinal fins on melting stratification are analyzed. The phase change plate melting rate is calculated as the total melting mass divided by the total melting time. The melting uniformity of the phase change plate was determined by the liquid phase component gradient. The temperature inhomogeneity coefficient is used to determine the air uniformity after passing through the phase change plate. The main results are as follows: (1) The plain phase change plate (without fins) showed an abrupt temperature rise followed by stabilization during melting, with a concurrent shift in its liquid fraction curve; (2) Increases in fin length, transverse fin number, and longitudinal fin number all improved the plate's melting rate and temperature uniformity, with maximum improvements of 10.86% and 293%, respectively; (3) The PCP of the optimized method 1 has better melting uniformity, but the initial cost is higher than that of the optimized method 2.