Molecular Dynamics Simulation of Thermal Behavior of Ammonia Refrigerant in the Presence of Copper Nanoparticles

Abstract

Nanofluids are mixtures of a base fluid and nanoparticles (also known as nano-scaled particles), and they were used within advanced heat transfer applications with known aggregation issues as well as unreliability in performance. Molecular dynamics simulations can effectively look at nanofluid behavior with no disruptions, especially when considering the complications and limitations involved with performing experiments at the nano-scale. We conducted molecular dynamics simulations that investigate the thermal and atomic behaviors of a nanofluid, which involved ammonia nanofluids with copper nanoparticles in aluminum nanochannels. Our results focused on evaluating the outflow of the nanofluid and on determining the primary factors including maximum velocity, temperature heat flux and nanoparticle aggregation time while modifying the initial conditions of temperature (300-350 K), and pressure (1-5 bar). Furthermore, we found the thermophysical properties of the nanofluids were heavily dependent on the initial temperature and pressure. By improving the initial temperature and pressure, thermal systems can support the promotion of efficiency and sustainability. We also measured the kinetic and potential energies, with the potential energies measuring -8399.15 eV and 80.69 eV after 5 ns with no indications of structural instabilities. The results indicated that as the initial temperature was increased, maximum velocity increased from 0.00086 to 0.00099 Å/ps and maximum temperature increased from 240 to 258 K. Furthermore, heat flux decreased from 1411 to 1397 W/m² and aggregation time decreased from 3.96 to 3.93 ns. On the other hand, maximum velocity decreased to 0.00078 Å/ps and maximum temperature decreased to 234 K, as well as heat flux increased to 1436 W/m² and aggregation time increasing time was increased to 4.07 ns, with the increasing initial pressure. These results provided some insight into the optimization of nanofluids for energy conserving thermal control, by varying operating conditions, and offered implications for sustainable engineering applications. © 2025 The Author(s)