Synergistic impact of horizontal fin installation height and nanoparticle volume fraction to enhance charging performance of phase change materials (PCMs)

Abstract

This study numerically analyses the synergistic influence of nanoparticle and orthogonal fin on heat transfer performance of phase change materials using enthalpy-porosity method. The natural convection heat transfer and heat conduction during the melting process are coordinated by varying nanoparticle volume fraction and installation height of fin. Results illustrate that the optimal installation height of horizontal fin and nanoparticle volume fraction is 8.9 mm and 1.0 vol%, respectively. The corresponding total melting time is 1024 s and average energy charging rate is 484.5 W. Compared with the optimum conditions without nanoparticle (φ = 0.0 vol% and d = 7.0 mm), total charging time is reduced by 29.8% and average charging rate is increased by 51.1%. The equivalent Nusselt number demonstrates that the addition of high volume fraction nanoparticle decreases the convective heat transfer intensity. The low volume fraction nanoparticle enhances PCM thermal conductivity and has an insignificant effect on natural convective heat transfer. The Prandtl number demonstrates that when the volume fraction is 1.0 vol%, the effect of increasing thermal conductivity on strengthening heat conduction is greater than the negative effect of decreasing natural convection heat transfer caused by viscosity. Effective design guidelines to improve thermal charging performance of PCM-based LHTES devices are finally provided.