Melting kinetics of PCM under synergistic effects of passive nanoparticle addition and active electric field exposure

Abstract

Present study numerically investigates the impact of electric field exposure and nanoparticle addition on the melting kinetics of a phase change material (PCM), crucial for cooling and energy storage applications. A two-way coupled numerical model considering the reciprocal effects of the electric field on melting, and vice versa is employed. The enthalpy-porosity technique models the melting process, while an effective properties-based single-phase approach is adopted to model the nanoparticle enhanced phase change material (NEPCM). Specifically, the focus is on the melting dynamics of (Al2O3 - octadecane) NEPCM in a classical differentially heated cavity under the influence of a horizontal electric field, inducing electrohydrodynamic (EHD) flow in the PCM’s liquid region. Parameters varied include nanoparticle volume fraction (ϕ) from 0 to 5% and the applied voltage from 0 to 20 kV. Individual and synergistic influences of nanoparticle addition and the application of an electric field are investigated. The introduction of nanoparticles induces viscous damping effects, manifesting in diminished rates of melting, reduced heat transfer coefficients, and restrained energy storage capacities. Conversely, the imposition of an EHD flow mechanism amplifies fluid velocities, augments convective mixing, and enhances overall heat transfer rates. In the absence of an electric field, the presence of nanoparticles in NEPCM (ϕ=5%) leads to a notable reduction in key performance metrics. Specifically, the maximum melt fraction, mean Nusselt number, and stored energy experience a substantial decline of 50% when compared to the performance of the base PCM. However, the introduction of an electric field serves to ameliorate these adverse effects, facilitating an acceleration in the melting process, elevating the mean Nusselt number, and bolstering energy storage capacities within NEPCMs to levels commensurate with those observed in pure PCM. Consequently, for applications focused on energy storage, the utilization of pure PCM in conjunction with an electric field emerges as a viable strategy. Conversely, heat sink applications necessitating controlled and gradual melting processes are better served by the natural convection melting of NEPCMs. Notably, for thermal management applications necessitating uniform and high-intensity dissipation of heat flux, the combination of NEPCMs with an electric field is recommended, as it affords enhanced heat transfer capabilities whilst ensuring uniform dissipation of thermal energy. Present study provides insights on the melting characteristics of a NEPCM under the influence of an electric field which will aid in application of electric field assisted melting of NEPCM in real time engineering applications.