Ice thermal energy storage enhancement using aligned carbon nanotubes under external magnetic field

Abstract

In this work, the magnetic Multi-walled Carbon Nanotubes (MWCNTs) with the magnetization range of 27.6–55.6 emu/g were prepared. It is indicated the aligned MWCNTs are distributed along with the magnetic field direction, and their ultra-high thermal conductivity at the axial direction could be fully utilized. Furthermore, the effect of magnetic field on ice thermal energy storage using aligned MWCNTs was studied. Specifically, the solidification characteristics including nucleation and solidification phase change process under various magnetic field intensities were investigated experimentally and theoretically. The results showed the optimal magnetic field intensity exists for aligned MWCNTs Phase Change Material (PCM), at which PCM has the lowest supercooling degree, the shortest solidification phase change time, and phagocytosed MWCNTs by growing solid-liquid interface. The optimal magnetic field intensities are 150 mT, 100 mT, 75 mT, 75 mT with increased mass ratios of Fe3O4 on the wall of MWCNTs from 1:1 to 4:1, and their supercooling degree are decreased by 36.0 %, 46.5 %, 70.0 %, 65.1 % compared with pure water. For solidification phase change process, the results showed that nearly 50 % of the aligned MWCNTs PCM is solidified in 25 % of the total solidification time. It is concluded aligned MWCNTs fully exhibited nucleating agent and the heat transfer enhancement as they uniformly distributed in the PCM under optimal magnetic field intensity.