Advances in phase change materials, heat transfer enhancement techniques, and their applications in thermal energy storage: A comprehensive review

In recent years, phase change materials (PCMs) have attracted considerable attention due to their potential to revolutionize thermal energy storage (TES) systems. Their high latent heat storage capacity and ability to store and release thermal energy at a constant temperature make them promising candidates for TES applications. However, challenges such as low thermal conductivity, supercooling, phase segregation, leakages, corrosions, and slow charging/discharging rates have prompted the development of various PCM modification techniques and heat transfer enhancement methods. This review provides an overview of recent advances in PCM technologies from 2010 to 2023. It encompasses the development of new PCMs with high thermal conductivity, shape stability, and durability, as well as exploring novel TES storage methods to enhance charge/discharge rates. The review comprehensively discusses different types of PCMs, including paraffins, non-paraffins, sugar alcohols, hydrated salts, molten salts, and metals. It aims to understand their unique characteristics, compare their costs, sustainability, and applicability, and delve into the associated phase transitions between states and eutectics. Furthermore, the review covers shape stabilization and encapsulation of PCM, along with the elaboration on applications and the effect of process parameters during modification. While shape stabilization is generally easier to produce and control, encapsulation can provide better protection and isolation to the PCM core. To implement PCM-based heat transfer systems effectively on a commercial scale, passive methods (e.g., fins and nanoparticles) and active methods (e.g., external fields and rotation) are also explored. Additionally, it elaborates on the pros, cons, and relevant applications of emerging heat transfer enhancement techniques for PCM technologies. The review highlights that various enhancement methods can be combined in a system to achieve optimal charging/discharging rates, ultimately aiming for phase transition congruency. Overall, this review serves as a valuable resource for researchers and engineers working in the field of PCM-based thermal energy storage.