Heat transfer enhancement in phase change materials (PCMs) by metal foams and cascaded thermal energy storage

Abstract

Low heat transfer performance has been the main problem restricting the use of Phase Change Materials (PCMs) in situations requiring rapid energy release or storage. Three innovative solutions are studied in this Thesis to improve heat transfer in PCMs. These include combining PCMs with metal foams, Cascaded Thermal Energy Storage (CTES) and Metal Foam-enhanced Cascaded Thermal Energy Storage (MF-CTES). Heat conduction is investigated in Chapter 3, in which it was found that metal foams can improve heat conduction of PCMs by 5–20 times. Natural convection is investigated in Chapter 4, in which metal foams were found to suppress natural convection due to their large flow resistances. Nevertheless, metal foams can still achieve a higher overall heat transfer rate (3–10 times) than PCMs without metal foams. CTES is examined in Chapter 5, with results showing that CTES has a higher heat transfer rate (30%) and a higher exergy transfer rate (22%) than Single-stage Thermal Energy Storage (STES). MF-CTES is proposed in Chapter 6; this is, to the best knowledge of the author, the first time that it has been investigated. MF-CTES was found to further improve the heat and exergy transfer of CTES by 2–7 times, meanwhile reducing melting time by 67%–87%