Development and thermal characteristics of phase change nanoemulsions for low-temperature thermal energy storage

Using ethylene glycol solution as the base fluid has demonstrated its effectiveness in reducing the freezing point of the continuous phase in phase change emulsions. This, in turn, enhances the stability of the emulsion at low temperatures, which has significant implications for applications requiring emulsions in such conditions. However, there is a notable absence of comprehensive studies on this topic. In this study, we utilized the phase conversion method to prepare hexadecane emulsions with varying mass fractions, using ethylene glycol aqueous solution as the base fluid. The impact of the ratio of hexadecane to surfactant and the formulation of the surfactants on the dispersion stability of the emulsions were systematically investigated and optimized. Furthermore, the phase change and thermal properties of the emulsions were examined. Based on these results, the energy storage capacity and pumping power of the emulsions were calculated and compared with those of the base fluid. The results indicate that as the mass fraction of phase change material (PCM) increases, the energy storage capacity and viscosity of the emulsions also increase, while the thermal conductivity decreases. Additionally, the energy storage capacities of the emulsions surpass that of the base fluid, and the pumping power is reduced at relatively low PCM mass fractions and within the heat storage temperature range. The appropriate mass fraction of PCM were determined by comparing these outcomes.