Experimental analysis of the impact of nanoinclusions and surfactants on the viscosity of paraffin-based energy storage materials

Phase change materials (PCMs) are commonly used in many applications, including the transient thermal management of electronics. For many systems, paraffin-based PCMs are used with suspended nanoinclusions to increase their effective thermal conductivity. The addition of these materials can have a positive impact on thermal conductivity, but can also increase the viscosity in the liquid phase. In this paper, the impact of different nanoinclusions and surfactants on the dynamic viscosity of a common paraffin wax PCM is quantified in order to determine their suitability for thermal energy storage applications. The effect of the nanoparticles on the viscosity is found to be a function of the nanoparticle type with multiwalled carbon nanotubes (MWCNT) yielding the greatest increase in viscosity. The addition of both nanoparticle and surfactant to the base PCM is found to affect the viscosity even when the loading levels of the nanoparticles or surfactant alone are not enough to affect the viscosity, thus the combination must be carefully considered in any heat transfer application.