Synthesis and thermal properties of n-tetradecane phase change microcapsules for cold storage

Due to the high heat carrier density, latent heat functional fluid may be used as the secondary refrigerant in air conditioning system. In this study, two-step in-situ polymerization method is used to synthesis microcapsules of ploy (urea-formaldehyde) (UF), where n-tetradecane is used as core material and SDS as emulsifier. Microcapsules with excellent morphology and performance are obtained by adjusting the emulsifier mass fraction, stirring rate, polymerization PH value and core-shell mass ratio. The experimental results show that when the mass fraction of SDS is 1.2 wt%, the initial PH value is 3.5 and the core-shell mass ratio is 2: 1, phase change microcapsules have good dispersibility. The phase change enthalpy of the microcapsules reach to 178.1 J·g−1, whose encapsulation rate is up to 85.6%. A latent heat functional fluid is prepared using the synthesized microcapsules and the base liquid of water and absolute ethanol. When the ethanol mass fraction in the base fluid is about 74 wt%, the stable latent heat functional fluid is obtained. The thermal conductivity of the latent heat functional fluid increases with the increase of temperature, and decreases with the increase of the mass fraction of microcapsules. Its viscosity rises with the increase of temperature or the mass fraction of microcapsules.