Thermal performance of octadecane as phase change materials in circular tube applying molecular dynamics simulation: the effect of initial temperature

This study examines the thermal properties of phase change materials (PCMs) using molecular dynamics simulation, concentrating on a cylindrical system including octadecane and water as PCMs. The study was executed in two phases: atomic structure equilibration and thermal analysis. During equilibration, the system's potential and total energy reached stability at 10 ns, confirming thermodynamic equilibrium for future study. The thermal analysis phase investigated the impact of altering the initial temperature (IT) on the system's charging and discharging behavior. Raising the initial temperature from 300 to 350 K resulted in a decrease in charging time, from 6.58 to 6.16 ns, attributable to improved atomic mobility and increased frequency of atomic collisions. At elevated temperatures, atoms gain more kinetic energy, promoting accelerated energy transfer and enhanced energy absorption efficiency. The raised temperature induced alterations in the system's atomic characteristics: atomic density diminished owing to thermal expansion, while the average atomic velocity and system temperature escalated in reaction to heightened atomic energy. Furthermore, the elevated temperature enhanced the thermal efficiency of the system, as seen by augmented heat flow and thermal conductivity. These enhancements resulted from accelerated atomic motion and more effective energy dispersion inside the material. The study shows that elevating the initial temperature significantly improved the thermal efficiency of PCM systems, providing critical insights for the optimization of thermal storage and heat management systems.