Experimental study on thermophysical properties of water-based nanoemulsion of n-eicosane PCM

In the present study, the thermophysical properties of water-based nanoemulsion of n–eicosane, including density, dynamic viscosity, thermal conductivity, and specific heat, are experimentally measured. The effects of mass fraction of n–eicosane suspensions in the range of 0 to 10 wt%, temperature of nanoemulsion from 10 °C to 45 °C, and shear rate in the range of 300 s⁻¹ to 660 s⁻¹ on these thermophysical properties are studied. The results showed that inside the phase change region, the nanoemulsion with higher mass fraction of the n–eicosane suspensions has a higher latent heat value and accordingly, this leads to higher specific heat. In addition, outside of the phase change region, the specific heat reduces with increasing the mass fraction of n–eicosane suspensions. As the temperature is increased from 25 °C (when the n–eicosane suspensions are solid), the thermal conductivity improves and by approaching the phase change period of the n–eicosane suspensions, this improvement trend is intensified. However, the melting process of n–eicosane suspensions in the nanoemulsion begins at temperature of 35 °C and this leads to a considerable decrease in the thermal conductivity around this temperature. The shear stress of pure water increases up to 139% with increasing the shear rate in the range of 300 s⁻¹ to 660 s⁻¹. This increase is about 113% for the case of water-based nanoemulsion of n–eicosane with the mass fraction of 10%. The density of water-based nanoemulsion of n–eicosane is lower as compared with the pure water. In addition, the density of nanoemulsion also decreases as the mass fraction of n–eicosane suspensions increases. Based on the results obtained in this study, the water-based nanoemulsion of n-eicosane PCM has the great thermophysical properties and it can be used for the energy transport and storage in different thermal systems.