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.