Effect of electric field on melting characteristics of nano composite phase change material: A numerical study

The phase change materials (PCM) are having tendency to store thermal energy during its melting (charging) and release this during solidification (discharging) process. Among many materials, organic phase change materials are most suitable for different engineering applications due to their better thermal stability over repeated phase change cycles. However, their low thermal conductivity limits the energy storage capacity. Adding nanoparticles alone is not sufficient to improve its energy storage performance significantly due to weak convection current. Therefore, a numerical investigation is done here to study the energy storage performance improvement of PCM nanocomposites using an external electric field. The governing energy and momentum transport equations along with Poisson's equation for electric potential and Nernst-plank equation for charge conservation are solved numerically using the finite volume method. A source based implicit enthalpy model is adopted for modeling the phase change of PCM. The effect of nanoparticle concentration, Electric Rayleigh number, charge injection number, thermal Rayleigh number and effect of dielectric force on melting characteristics of PCM nanocomposite were studied. It is found that there is significant improvement in melting rate of nanocomposite containing 5 % nanoparticles with 28 % increase in the liquid fraction. Moreover, Due to electric field, Coulomb force plays a great role in improving the heat transport when natural convection is weak and there is an enhancement of 50 % liquid fraction at Rayleigh number of 1 × 103. It is observed that even at zero gravity, the effect of electric field shows 90 % melting fraction of phase change materials in the cavity. The effect of charge injection has a significant role in enhancing the melting of PCM nanocomposite. There is also a comparative study of both Coulomb force and dielectric force. It is found that the dielectric force has no such effect on improving the melting of PCM nanocomposite.