Investigating the effect of the number of layers of the atomic channel wall on Brownian displacement, thermophoresis, and thermal behavior of graphene/water nanofluid by molecular dynamics simulation

Abstract

Nanofluids (NFs) are nanoscale colloidal suspensions containing dense nanomaterials. They are two-phase systems with solid in liquid phase. Due to their high thermal conductivity, nanoparticles increase the thermal conductivity (TC) of base fluids, one of the basic heat transfer parameters, when distributed in the base fluids. The present research investigates the thermal behavior, Brownian motion, and thermophoresis of water/graphene NF affected by different numbers of atomic wall layers (4, 5, 6 and 7) by molecular dynamics (MD) simulation. This investigation reports changes in heat flux (HF), TC, average Brownian displacement, and thermophoresis displacement. By raising the number of atomic wall layers from 4 to 7, the average Brownian displacement and thermophoresis displacement increase from 3.06 Å and 23.88 Å to 3.62 and 25.05 Å, respectively. Increasing the number of layers due to the decrease in temperature increases the temperature difference between the hot and cold points along the channel. It increases the Brownian motion and the maximum temperature. Additionally, by raising the atomic layers of the channel wall, the values of HF and TC increase from 39.54 W/m2and 0.36 W/mK to 41.18 W/m2and 0.42 W/mK after 10 ns, respectively. The temperature rose from 1415 to 1538 K. These results are useful in different industries, especially for improving the thermal properties of different NFs.