Analysis of different phase change materials (PCMs) and wall material in a nano-circular space thermal energy storage (TES) system: A molecular dynamics approach

Abstract

Thermal energy storage (TES) play a vital role in overcoming the fluctuating nature of solar thermal energy. To study and understand the performance of these systems, using new techniques such as computer simulations can be useful. In this article, a specific circular nanochannel containing a phase change material (PCM) is introduced and its thermal and mass performance are investigated. By using two types of PCM and three wall metals (platinum, copper, and aluminum) the effects of changing several geometric and thermodynamic parameters are evaluated. In general, two different plans are proposed and parameters such as thermal conductivity, heat flux, charging, and discharging time are defined and evaluated. The obtained results show that the use of paraffin reduces the phase change time from 1.36 ns to 1.21 ns. Geometrical investigations also show that increasing the diameter ratio leads to a decrease in heat flux. Increasing the velocity of argon atoms in the inner tube also leads to an increase in the mobility of atoms and as a result improves the heat transfer rate. Using copper, the thermal conductivity is 54.3 % and 13.5 % higher than platinum and aluminum. The maximum heat flux for the two proposed cases is about 1500 and 1285 W/m2, respectively. Increasing the velocity of argon atoms from 0.01 Å/fs to 0.05 Å/fs leads to a decrease in the phase change time from 1.12 ns to 1.15 ns. Regarding the type of PCM, paraffin performs better than the combination of water-hydrocarbon.