Performance enhancement of latent heat storage systems by using extended surfaces and porous materials: A state-of-the-art review

Abstract

Latent heat thermal energy storage (LHTES) is a widely accepted technology because of its high energy density at nearly constant operating temperature. The main disadvantage of LHTES is the low thermal conductivity of the storage material, which affects the charging and discharging rates. Therefore, various methods have been used for enhancement of thermal performance of phase change materials in LHTES including utilizing fins and porous materials with high thermal conductivity. These two main methods are intensively addressed in the literature. In this paper, these techniques are reviewed and discussed by classifying them regarding their prominent specifications. First, the enhancement by extended surfaces is reviewed focusing on the fin geometries. Secondly, metal foams are investigated with respect to the materials they are made of and their structure such as gradient or partial porosity since these techniques are promising methods for significant performance augmentations. Thereafter, in the following section, the combination of these two techniques, which can be called a hybrid technique, is examined and recent research works are reviewed. The literature review showed that innovative fin shapes are increasingly investigated by numerical simulations. However, there is a significant need for experimental validations. On the other hand, metal foams exhibit remarkable thermal performance, nevertheless, their utilization is not as prominent as fins since utilization of fins is a simpler and cost-effective method. Combining these two methods is recently getting increasing attention as it can further improve thermal performance of PCMs. After reviewing the relevant recent studies, conclusions drawn from the present literature study are outlined. Additionally, some directions and recommendations for future research are highlighted at the end of the paper.