Thermal Performance of Octadecane as a Phase Change Material in a Circular Tube: The Effect of External Heat Flux via Molecular Dynamics Simulation

Abstract

Phase change materials are a modern and effective technology in thermal energy systems. This paper investigates how external heat flux changes affected the thermal and atomic properties of octadecane as a phase change material to concentrate solar thermal energy and to store it. Alteration in the behavior of simulated samples was explored using maximal temperature, velocity, density, charging, discharging, heat flow, thermal conductivity, and thermal stability metrics. The first structure was subjected to varying external heat fluxes of 0.01, 0.02, 0.03, and 0.05 W/m2 during the early phase. The results suggest that increasing EHF (Effective Heat Flux) resulted in better atomic mobility, leading to increased molecular dynamics and improved heat transport characteristics. This is because elevated heat flow prompts atomic motion, causing the temperature to rise to 568.08 K, while raising the velocity to 0.0082 & Aring;/fs, and lowering the density to 0.028 atoms/& Aring;3. In addition, increased heat flow is associated with improved charging efficiency, and reduces charge time to 6.41 ns, while discharging time increased to 7.17 ns because of extended thermal energy discharging. Finally, thermal conductivity and heat flow increased to 1.71 W/m & sdot;K, and 5.96 W/m2, respectively. The changes improve thermal conductivity and overall heat transfer efficiency. The results are crucial in optimizing phase change material-based thermal management systems for applications requiring regulated energy dissipation and storage under variable thermal loads.