不凝性气体对纳米通道内水分子流动传热影响的分子动力学模拟

Molecular dynamics simulation of effect of non-condensable gases on heat transfer of water molecule flow in nanochannels

随着电子元件高性能化和小型化的发展,纳米通道内工质的流动传热问题受到了更多的关注.本文采用分子动力学模拟方法,模拟了300,325,350 K的纳米通道中流体的流动传热情况,工质为水,水中不凝性气体用氩气代替.结果表明:流动过程中,氩原子形成高势能团簇,随着温度升高,流体势能上升,团簇逐渐减小或消失;少量气体原子能够促进流动,而较多氩气会导致通道中心区域形成较大气体团簇而阻碍流动,同时,被加热的工质能显著减小流动阻力系数;近壁面区域流体温度高于中心区域,团簇内部原子活动更加剧烈,平均分子动能更大,温度更高;水的氢键结构可以促进纳米通道内的传热,氩原子会影响氢键数量,高温会破坏水分子形成的氢键网络,使努塞尔数下降.本研究分析了不凝性气体影响下微通道内水分子流动传热的机理,为电子设备的强化传热提供了理论指导.

With the development of higher performance and miniaturization of electronic components,the flow heat transfer of working fluids in nanochannels has received more attention.To elucidate this phenomenon,molecular dynamics simulations are used to simulate the behaviors of fluids within nanochannels at temperatures of 300 K,325 K,and 350 K.Water serves as a flow medium,with argon substituted for any non-condensable gases.In the flow process,argon atoms aggregate into clusters that are characterized by high potential energy.As the temperature rises,the concomitant increases in the fluid’s potential energy,which leads to the gradual diminution or complete dissipation of these clusters.A minor presence of gas atoms can facilitate fluid movement;however,an excess of argon promotes the formation of larger gaseous clusters in the central region of the channel,thereby impeding fluid flow.Concurrently,the application of heat to the fluid appreciably diminishes the coefficient of flow resistance.The temperature of the fluid in the near-wall region exceeds that of the central area.In the clusters,the atoms exhibit heightened activity,leading to an increase in the average molecular kinetic energy and a concomitant rise in temperature.The inherent hydrogen-bonding structure of water enhances heat transfer within the nanochannels.Argon atoms exert an influence on the number of hydrogen bonds,and rising temperatures disrupts the hydrogen-bond network established by water molecules,ultimately leading to a decrease of the Nusselt number.This investigation offers insights into the heat transfer dynamics of water molecular flow within microchannels under the perturbation of non-condensable gases,thereby furnishing theoretical guidance for enhancing heat transfer within electronic devices.