Heat Transfer Enhancement Techniques in Latent Heat‐Based Cold Thermal Energy Storage for Long‐Term Cold Storage Applications: A Review

ABSTRACT Various heat transfer augmentation techniques have been investigated to address the low thermal conductivity nature of phase change materials (PCMs). However, the techniques may also accelerate the heat exchange between the system and its surroundings, which increases the heat leak into the system during the cold holding process, particularly in prolonged cold thermal energy storage (CTES) systems. Hence, comprehensive evaluation is crucial for researchers to develop enhancement techniques that enable faster charging and slower discharging rates. This review comprehensively evaluates different passive heat transfer enhancement techniques, including fin addition, storage container optimization, nanomaterial dispersion, metal foam embedding, and hybrid methods. It identifies enhancement methods and their key parameters and factors favorable for prolonged CTES systems, based on their distinct impacts on the melting and solidification rates. The review reveals that incorporating nanomaterials at higher concentrations, metal foams with lower porosities, and convective flow restricting fins demonstrate higher solidification and slower melting rates, resulting in faster charging and prolonged cold retention durations. In contrast, adding fins that facilitate natural convection and embedding metal foams with higher porosities exhibit comparable melting and solidification rates. Additionally, the review includes performance limitations and life‐cycle aspects of enhanced PCMs. Moreover, various techniques, including spatiotemporal PCMs, form‐stable cold thermal energy storage phase change materials (FCPCMs), and double‐layer insulations, significantly improve the cold retention duration of PCMs used in long‐term CTES systems. It also highlights the challenges and future prospects, focusing on developing phase change CTES systems for prolonged cold storage, emphasizing performance, cost‐effectiveness, scalability, and sustainability.