Abstract

Over the last years, nano-enhanced Phase Change Materials (nano-PCM ) have lately attracted a great attention to address many key barriers (i.e., low electrical and thermal conductivities) to wide adoption of PCMs in emerging applications such as cooling systems, energy conversion, electronic devices, electrodes for rechargeable batteries. For all applications, the knowledge of the electrical properties is important. In this work, a numerical setup was built to investigate the electrothermal behavior of the nanocomposite graphene/paraffin wax. This new materials are developed by associating paraffin wax as thermal storage material and graphene nanoparticles as conductive fillers.The finite element method based on COMSOL Multiphysics 5.2a software, was used to solve the coupled equations of various physical phenomena: electric current, heat transfer and phase change process of the paraffin. To understand the physics-based mechanisms during current distribution, a multi-scale numerical models were developed, where the homogeneous mode is used in macroscopic scale and heterogeneous one in microscopic scale. The choice of optimal physical properties of these materials is analyzed to predict the effective electrical and thermal conductivities of the composite system. The numerical results indicate that the improvement of electrical conductivity of the composite is due to the formation of a conductive network inside the paraffin wax. The resulting current passing through the graphene nanoparticles produces joule heat and self melting of paraffin wax. Accordingly, electric heating behavior of the nanocomposite is strongly dependent on graphene concentrations as well as applied voltage.

Keywords: Numerical study; Graphene nanoparticles; Electrothermal behavior; Nanocomposite materials; Phase change material