Experimental and numerical investigation of a hybrid PCM-air heat sink

The present work deals with a combined device in which the heat may be both absorbed by a phase-change material (PCM) and dissipated to the ambient air. Accordingly, the heat sink, made of aluminum 6061, has compartments where the PCM (eicosane C₂₀H₄₂) is stored and fins exposed to the air. The experiments are performed in both room- and elevated-temperature environment. A simplified thermal model, based on a two-dimensional enthalpy formulation for the PCM, is developed for a conservative estimation of temperature evolution. The results, presented in terms of base temperature (experimental and numerical) and PCM melt fraction (predicted), show a fairly good agreement between the experiments and simulations. Also shown are some findings obtained using a more complex model, which accounts for convection in the melt. A dimensional analysis yields the melt fraction and Nusselt number as functions of the Fourier and modified Stefan numbers. It also addresses the relative contributions of latent/sensible accumulation and heat transfer to the air. The dimensionless curves for latent-heat-based accumulation rate are rather similar in various cases. On the other hand, it is found that the share of sensible-heat-based accumulation rate tends to increase when the heat input increases.