Preparation and Thermal Properties of Latent Functional Thermal Fluid Based on Size-Controllable Phase Change Nanocapsules

Abstract

Size-controllable 1-octadecanol@polystyrene phase change nanocapsules (NEPCMs) were prepared using the miniemulsion polymerization and dispersed in deionized water containing multi-walled carbon nanotubes to prepare a latent functional thermal fluid (LFTF). The results demonstrate that the NEPCMs exhibit a typical core-shell structure. The average particle size (55.28-143.8 nm) of the NEPCMs can be regulated by controlling the content of compound emulsifiers. The optimal phase change enthalpy has an excellent heat storage capacity of about 222.7 J/g, the packaging rate is up to 80.63%, and the average particle size is about 88.3 nm. The heating/cooling cycle results show that NEPCMs have excellent cycle stability. LFTF containing 10 wt% NEPCMs was considered the optimal choice for its excellent photothermal conversion efficiency (up to 64.91%), excellent dispersion stability (zeta potential 39.17 mV) and thermal storage capacity (peak specific heat capacity 5.72 J·g-1·K-1). Under the influence of solar radiation, the temperature rise curve of LFTF exhibited a rapid initial warming rate followed by a plateau period of approximately 76 minutes upon reaching the melting point of the NEPCMs, whose photothermal conversion efficiency is roughly 2.18 times that of water. The experimental findings demonstrate the potential application of LFTF based on NEPCMs in the solar thermal industry.

Keywords: Phase change nanocapsules, Latent functional thermal fluid, Size-controllable, Solar Energy, Photothermal conversion.