Preparation and thermal properties of nano-microcapsule and simulation heat storage application

Abstract

The prevention of material leakage and improvement of thermal conductivity are very important for thermal energy storage application. In this work, nano-TiO2@n-docosane microcapsules were synthesized by the fine emulsion interface polymerization method using tetra-n-butyl titanate (TBT). This approach enhances the encapsulation rate and efficiency of phase change microcapsules. The microcapsules formation process was observed using a biological microscope. The diameter of the microcapsules decreased significantly with the increase of stirring rate. The phase transition temperature of the optimal microcapsules is 42.4 °C. The encapsulation rate and efficiency reach up to 90.7% and 91.0%, respectively. The average thermal conductivity of nano-TiO2@n-docosane microcapsules is 215% higher than that of n-docosane. SEM and infrared spectroscopy testing results confirm the successful coating of n-docosane by TiO2. Thermogravimetric analysis presents that TiO2 forms a shell, which reduces the leakage of n-docosane. The melting and solidification processes of n-docosane and nano-TiO2@n-docosane microcapsules were simulated numerically. In comparison to n-docosane, nano-TiO2@n-docosane microcapsules exhibit a 14.89% increase in peak storage power and a 12.47% increase in heat transfer coefficient during charging. Additionally, during discharging, these values rise by 3.23% and 6.46%, respectively. Nano-TiO2@n-docosane microcapsules enhance heat transfer and the charging/discharging process of phase change materials.