A review on heat transfer enhancement techniques for PCM based thermal energy storage system

Phase change materials (PCMs) are widely used from a heat storage perspective because of high-energy storage density at a nearly constant temperature. The main disadvantage of phase change material is the low response to heat transfer rate because of low thermal conductivity. Enhancing the heat transfer rate in PCM reduces the charging and discharging durations, which makes them more suitable for energy storage. Various conventional and newest methods are used to enhance the performance of phase change materials. Heat transfer enhancement has been investigated using different shapes and orientations of fins arrangement. The effect of modifying geometry on heat transfer rate has also been investigated. The effect of the arrangement of PCMs of various melting points on charging and discharging duration has been investigated. Others promising heat transfer enhancers based on carbon and metal material have been examined. Thermal properties analysis of expanded graphite, carbon fiber, and carbon nanotubes in the category of carbon-based material and metal foam, nanoparticle, and metal oxide in the group of metal-based material has been extensively studied. The effect of various heat transfer enhancement technique on PCMs supercooling was also studied. The literature review showed that the use of fins is the most common heat transfer enhancement media in concentric tube heat exchangers due to low cost and simplicity in usage and the use of various shapes and orientations gives a better thermal performance. The effect of geometry modification has been shown to have a promising effect in heat transfer enhancement because of more heat transfer area available to transfer heat without reduction in the mass of PCM. A cascaded system has been found to be effective in efficiently utilizing the energy of heat transfer fluid in the charging and discharging cycle. Metal foam material has been found to have a very high heat transfer rate in PCM but at the cost of a reduction in the storage capacity of PCM. The effect of various weight per cent loading of carbon fiber, carbon nanotube, graphene, nanoparticle, and metal oxide was investigated. Graphene was found to be better heat transfer media due to having a high thermal conductivity value.