Characterization and experimental investigation of composite phase change materials based on aluminum nitride/expanded graphite

Phase change heat storage technology is a good way to solve the problem that the temperature of solar hot water outlet is affected by time domain. Polyethylene glycol (PEG) is a potential phase change material, but it still has the disadvantages of low thermal conductivity and poor heat transfer performance. In this study, a new porous aluminum nitride matrix material with enhanced thermal conductivity was prepared by cellulose sintering method, and composite phase change material (P4ALN) was prepared by vacuum adsorption of PEG4000. P4ALN has the problems of low enthalpy and large particle gap. Therefore, composite phase change material P2EG (polyethylene glycol 2000 adsorbed by expanded graphite) was prepared. P2EG and P4ALN were mixed in a mass ratio of 9: 4 to form a third particle (MIX), which not only ensured high thermal conductivity, but also improved the enthalpy of the material. SEM, FT-IR, DSC, TG, thermal conductivity, heat storage and release tests were carried out on the prepared composite phase change materials. The results showed that the composite phase change material has good adsorption, no chemical reaction among the components and good thermal stability at 190°C. DSC curve of MIX particles showed that it had the characteristics of double phase transition temperature, and compared with P4ALN, the enthalpy was increased by nearly 40J/g. Compared with pure PEG, the thermal conductivity of P2EG, P4AlN and MIX was increased by 11.21, 12.99 and 12.49 times, respectively. Heat storage and release experiments proved that the heat storage capacity of the composite material MIX briquetting was 1.55 and 1.60 times of P2EG, respectively, which can be used as a phase change heat storage material for solar hot water.