Abstract
Phase change materials (PCMs) have the advantage of using the latent thermal heat as energy storage. Coconut oil (CO) has attracted much attention as PCM due to its high stability against oxidation. Although the viscosity of CO-based dispersions has extensively been studied, little research has been performed on time-dependent flow behaviors. In this work, the rheological properties of fumed silica dispersed in CO at fractions of 1, 2, 3, and 4 vol.% were investigated. All suspensions showed shear-thinning behavior, which became more Newtonian at temperatures above the phase change. The 3 and 4 vol.% suspensions showed gel-like microstructures. The thixotropic properties of the 3 vol.% suspension at 30 °C and 35 °C were mainly studied through stepwise changes in the shear rate. The results were consistent with thixotropic behavior, with a complete recovery of the microstructure. The sweep frequency of this sample demonstrated the dominance of the elastic modulus at both temperatures. Therefore, a thixoelastic nature of this gel could be inferred. This gel-like material flowed under high stress, providing superior thermal damping capabilities compared to conventional fluids. A reduction of 8.65 °C was confirmed after 30 min. of the laptop power supply operation.