A molecular dynamics study about the mechanisms of liquid thermal transpiration flow in nanotubes

M Sahebi and AR Azimian, INTERNATIONAL JOURNAL OF THERMAL SCIENCES, 136, 9-14 (2019).

DOI: 10.1016/j.ijthermalsci.2018.10.011

The possibility and the mechanisms of liquid transport in nanotubes by the effect of thermal transpiration phenomenon are discussed using molecular dynamics simulation (MD) method. Based on the results, it is demonstrated that the thermal transpiration flow for liquids can be established by imposing a temperature gradient to the wall of a nanoscale tube. It can be deduced from MD results that this flow is mainly due to the asymmetric pressure distribution in a narrow region near the tube wall. Fluid layering phenomenon near the wall together with the induced temperature gradient causes the potential component of the pressure in the narrow region near the cold side of the tube becomes higher than the hot side. This causes the fluid to flow in the direction of the temperature gradient. It is shown that the thermal transpiration flow is a plug-like flow. This phenomenon can be used in designing thermal pumps for fluids. The effect of several effective parameters in fluid pumping is investigated. Results show that increasing the imposed temperature gradient, decreasing the nanotube diameter and increasing the fluid-wall binding energy augments the thermal transpiration effect.

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