Nano-enhanced phase change materials (NePCMs): A review of numerical simulations

Dispersing thermally conducive nanostructures is an effective method to improve the thermal performance of phase change materials (PCMs). For this purpose, nanocarbons, nanometals, and nano metal oxides have been used to develop nano-enhanced phase change materials (NePCMs) with unique thermal properties. However, review papers focusing on the numerical simulations of NePCMs are still scarce. The present review provides a comprehensive overview of the latest numerical studies on NePCMs for thermal energy storage (TES). These studies are mainly based on single-phase approaches, and the simulation results largely depend on the used prediction models of effective thermophysical properties. Accordingly, the most common numerical methods and prediction models are reviewed to address their advantages and limitations. Then, the focus is placed on melting and solidification of NePCMs inside different containers, including rectangular cavities, tubes, cylinders, spheres, and annulus. In-depth insights are given into the effects of nanostructure type, morphology, size, and concentration on heat storage and release performance. The pros and cons of dispersing nanoparticles and other heat transfer enhancement techniques are also compared, such as mounting fins and using porous foams. Moreover, a critical discussion is presented to identify the reasons for the discrepancy between simulation and experiment, as well as the research gaps and future directions. This review aims to update the existing NePCM studies using different simulation techniques, and to reveal the basic phase change behavior of NePCMs from the reported results.