Using a Novel Solubility Parameter-Controlled Approach in Synthesizing Phase Change Materials Nanocapsules and Its Performance Evaluation in Heat Transfer Fluid Applications

Abstract

In this research, nanocapsules of polyethylene glycol (PEG) as the phase change material (PCM) were synthesized and used to prepare a heat transfer fluid. The phase change nanocapsules were prepared using a novel sequential sedimentation approach by controlling the core and shell solubility parameters through temperature changes in the solvent. These nanocapsules consist of a PEG core with a molecular weight of 2000, as the PCM, and a thermally conductive polystyrene/activated carbon (PS-AC) shell (PEG@PS/AC). Adding up to one weight percent of these nanocapsules in distilled water significantly improved the thermophysical properties of the heat transfer fluid. The specific heat capacity increased from 4300 J·kg⁻¹·K⁻¹ for pure water to 5800 J·kg⁻¹·K⁻¹ for the prepared heat transfer fluid. This represents a significant improvement of approximately 35 % compared to pure water. The thermal energy absorption also showed improvements of about 17 %. Furthermore, the thermal diffusivity of the heat transfer fluid was significantly reduced by 82 %, from 12 × 10^–7 for water to 2.17 × 10^–7 m²·s⁻¹ due to the latent heat absorption of the PCM used in the nanocapsule. Based on the results, it is suggested that the developed PEG@PS/AC nanocapsules be used in heat transfer fluids to effectively manage thermal energy.