SearchPublisher and Institutes
You are here: Home :: Area NEM :: Physics :: Thermodynamics
Khellil Sefiane, Martin Snodgrass, Annie Steinchen
Evaporation self-induced Marangoni motion in fed capillaries for volatile liquids in open air
Considerable work has already been undertaken to study the behaviour of an evaporating meniscus. Because of the complexity of the wetting process much work needs to be done to fully understand the phenomenon. Although it has been demonstrated that the shape of such an evaporating meniscus depends on the intermolecular stress field and forces intervening during the process, the exact determining factors, which dictate the wetting properties, remain not fully understood and quantified.
The shape of an evaporating meniscus at the exit of a capillary tube filled with a pure liquid evaporating in dry air is studied by measuring the curvature and the macroscopic steady wetting angle. Evaporation leads to strong thermocapillary convection, which in turn is closely coupled to the wetting properties. The aim of this work is to show the effect of thermocapillary forces on the shape of an evaporating meniscus. The experimental procedure controls the air temperature around the capillary as well as the capillary wall and bulk liquid temperature; the shape of the meniscus is studied for varied temperature conditions. Results show a strong correlation between the steady wetting angle during evaporation at pinned meniscus and an ad hoc defined Marangoni number. It has been observed that increasing the wall temperature would ultimately lead to a slow down of the thermocapillary convection. At a given wall temperature the convection stops. A model has been developed to account for diffusion in the vapour phase. The relevant dimensionless number is found to be the ratio between the partition factor and the Marangoni number.
Journal of Non-Equilibrium Thermodynamics, Walter de Gruyter
Print ISSN: 0340-0204
Volume: 29, 06/2004
Pages: 177 - 198