A comprehensive review on the properties of micro/nano-encapsulated phase change materials: Single- to multi-layered shells

The micro and nanoencapsulation of phase change materials, utilizing shell@core structures has emerged as a practical and efficient technology for enhancing thermal and photothermal performance of conventional heat transfer fluids. However, to promote the development and widespread adoption of Micro/Nano-encapsulated Phase Change Materials (M/N-ePCMs) as a highly efficient thermal, photothermal, and storage energy solution, it is essential to establish a deeper understanding of several properties. For this purpose, we have presented a comprehensive review of these properties across a variety of M/N-ePCMs, spanning distinct shell designs ranging from single- to multi-layered shells. In the realm of single-layered-ePCMs, it was found that for successful integration of M/N-ePCMs into industrial and engineering applications, determining the optimal shell-to-core weight is pivotal in achieving superior thermal conductivity and storage capacity. M/N-ePCMs at the optimal ratio can offer an economical alternative to conventional nanoparticles made from expensive materials. Furthermore, it was revealed that achieving an accurate and reliable prediction of thermophysical and phase change properties of M/N-ePCMs requires a through exploration of these properties, considering the influence of ePCM size and shape, shell/core type, and shell-to-core weight ratio. Both single- and multi-layered M/N-ePCMs, were found to outperform their single-layered counterparts including mechanical strength, storage capacity, latent heat, photothermal efficiency, leakage control, and thermal/electrical conductivity. The study also showed that shells modified with excellent photothermal materials displayed higher solar energy conversion and absorption. Nevertheless, an excessive amount of these materials can potentially reduce optical performance and hinder the formation of the desired core@shell structure.