Preparation of cold-storage microencapsulated phase change suspension: dispersion stability and thermal conductivity performance improvement

Microencapsulated phase change slurry has become a research hotspot in the field of cold energy storage due to its high latent heat and microconvection effects. However, its instability and low thermal conductivity limit its practical applications. This study adopted the phase-change microcapsules with a tetradecane core and a polymethyl methacrylate shell, which is suitable for the food preservation temperature range between 3 °C–8 °C. The effects of different kinds of carrier fluids, surfactant types and graphene concentrations on the materials thermal performance and thermal conductivity were explored experimentally. The results indicate that the optimal carrier liquids consisted of deionized water and isopropyl alcohol in a mass ratio of 3.58:4.24, with a carrier liquid density of 0.87 g/cm 3 . The phase-change microcapsule suspension maintained dispersion stability for 30 days when the hydrophilic-lipophilic balance value of the sodium dodecyl sulfate and Hexadecyl trimethyl ammonium chloride composite surfactant was 27.9 and their mass ratio was 1:1. The thermal conductivity and circulation stability of phase-change microcapsule suspensions were enhanced by incorporating highly thermally conductive two-dimensional graphene materials. The highest thermal conductivity reaches 0.3092 W/(m·K) with the graphene concentration of 1 wt%, representing a 7.26% improvement compared to the suspension without graphene. After 100 clod thermal cycles, the latent heat loss of the composite suspension remained within 14.5%, which means the graphene improved the cycle stability of the suspension. The study gives a reference for the preparation of high-efficiency energy storage functional fluids.