Enhancement of PCM solidification using inorganic nanoparticles and an external magnetic field with application in energy storage systems

摘要

Heat recovery is one of the solutions to reduce Carbon dioxide emission, and using latent heat thermal energy storage systems (LHTESS) can be a promising way for heat recovery. In the present article, for the first time, the effects of both inorganic nanoparticles as an additive to PCM (phase change materials) and magnetic field on the PCM solidification rate inside a porous energy storage system have been modeled. For this purpose, the mixture of CuO nanoparticles and water was used as NEPCM (nanoparticle-enhanced PCM), and an external magnetic field was applied to the system. The unsteady process of solidification inside the storage system was simulated by employing finite element method (FEM). The impacts of various parameters including Lorentz forces strength, CuO/water concentration, and Rayleigh number on the charging time have been evaluated. Solid fraction, temperature, and streamline contours have been plotted to study the solidification process locally. The results indicated that with augmenting the Hartmann number from 0 to 10, the solidification time was reduced up to 23.5% in average. On the other hand, the addition of nanoparticles to PCM with volume fractions up to 4% leads to, on average, a 14% decrease in the solidification time. The obtained results suggest to employ the magnetic field as an effective solution to accelerate the solidification in energy storage systems while to reinforce the influence of magnetic field; nanoparticles can be added to the PCM. Finally, the solidification time was correlated with three main design parameters, i.e. nanoparticle volume fraction, Hartmann and Rayleigh numbers with a mathematical expression. (C) 2019 Elsevier Ltd. All rights reserved.