Nano-PCMs for enhanced energy storage and passive cooling applications

It is well known that the heat transfer associated with a phase change process is much higher than sensible enthalpy change even in forced convection. In particular, the vaporization process has been widely studied because it exploits the highest heat transfer coefficient; this heat transfer mechanism is used in both passive (i.e. heat pipes) and active (i.e. refrigerating machines) cooling devices. However, the solid liquid phase change process is another interesting possibility to reject even high heat loads, especially when they are intermittent. The term Phase Change Materials (PCMs) commonly refers to those materials, which use the solid-liquid phase change process to adsorb and then release heat loads (Mancin et al., 2015). The present work aims at investigating the feasibility of a new challenging use of Aluminum Oxide (Al2O3) and Carbon Black (CB) nanoparticles to enhance the thermal properties: thermal conductivity, specific heat, and latent heat of pure paraffin waxes to obtain a new class of PCMs, the so-called nanoPCMs. The nano-PCMs were obtained by seeding 1 wt% of nanoparticles in paraffin waxes with melting temperatures of 20 degrees C and 25 degrees C. The thermophysical properties were then measured to understand the effects of the nanoparticles on the thermal properties of both the solid and liquid PCM. These new nano-PCMs can represent a feasible and interesting way to mitigate or eliminate the intrinsic limitations in the use of paraffin waxes as PCMs for both energy storage and passive cooling applications. (C) 2016 Elsevier Ltd. All rights reserved.