Ice slurry is a good cold storage medium with a large heat capacity and efficient heat transfer properties. In this study, a microemulsion was prepared with the addition of water, soybean oil as the oil phase, Tween-80 and AEO-3 as surfactants, and amyl alcohol as co-surfactants. The effects of the mass ratio of the oil phase to surfactant, hydrophilic and oleophilic balance of the surfactant(HLB value), and mass ratio of the surfactant to co-surfactant(Km value) on the water solubility of the microemulsion were investigated. A 1∶4 mass ratio of oil phase to surfactant, a 6∶4 mass ratio of Tween-80 to AEO-3(HLB value of 11.6), and a 2∶1 Km value were the best ratios for the preparation of the microemulsion. An ice slurry was prepared by selecting the microemulsion with 50% water content under the above mass ratios. The influence of ice crystal particle size on the melting process of the ice slurry was studied using ice crystal melting images. The grain size of the ice crystals gradually decreased with increasing melting time. The melting time of the ice crystal particles with large grain size was greater than that of the particles with small grain size. The effects of storage time and ice content on the grain size distribution and average grain size of the ice crystals were analyzed using ice crystal images of the microemulsion ice slurry stored for 1 h and 2 h. The longer the storage time, the larger the grain size of the ice crystals. The number of ice crystals decreased while the ice percentage factor did not change. For the same storage time, the higher the ice content, the faster the growth rate of the ice crystal particle size.

To solve the problems of the slow growth rate and low cold thermal energy storage density of refrigerant hydrates, the addition of surfactants is an effective way to promote hydrate formation. Three polyoxyethylene castor oil (EL) surfactants with different hydrophilic-lipophilic balance (HLB) values (EL-20, EL-30, and EL-60) were selected as promoters to study their effects on HCFC-141b hydrate formation. The experimental results showed that the EL series of surfactants significantly reduce the hydrate nucleation induction time. The system with a mass fraction of 1.5% EL-20 exhibited the shortest hydrate induction time of 73 min, and the stability of hydrate formation was good. The micelles formed by the EL surfactants provide more nucleation sites, which accelerate hydrate formation. The hydrate cold thermal energy storage density is related to the HLB value of the surfactants. The system with a mass fraction of 1.5% EL-20 had the maximum cold thermal energy storage density of 246.48 kJ/kg and the fastest hydrate growth rate of 5.06 kJ/(kg·min), as EL-20 had a suitable HLB value. There is a "memory" effect during hydrate formation and dissociation cycle. The system with a mass fraction of 1.5% EL-20 surfactant exhibited the most favorable performance during the hydrate formation and dissociation cycles. After seven hydrate formation and dissociation cycles, the increase in temperature remained stable during hydrate formation.

TiO₂-UF@ Tet microcapsules were prepared using a two-step method in which the advantages of organic and inorganic shell layers were combined. The effect of the mass fraction of TiO₂ on the performance of the composite-shell phase-change microcapsules was investigated. The morphology, chemical composition, and thermodynamic properties of the phase change microcapsules were investigated using biological microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, energy-dispersive spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The experimental results showed that the microcapsules formed by TiO₂ and UF using the two-step method had a good composite shell structure. The phase-transition temperature of the microcapsules decreased, the latent heat of the phase transition decreased, and the thermal conductivity increased continuously with an increase in the mass fraction of TiO₂. The prepared microcapsules had smooth surfaces, a uniform particle size distribution, and an average particle size of approximately 2.0 μm. The phase transition temperature and latent heat of the optimal composition were 3.1 ℃ and 168.5 J/g, respectively, with a coating rate and coating efficiency of 71.64% and 69.08%, respectively. After 100 heating cycles, the phase-transition temperature remained stable and the microstructure was good. These microcapsules are suitable for cold-storage air conditioning systems.