Evaporation au sein d'un tube de section polygonale : Influence des écoulements microcapillaires le long des coins

Evaporation within a non circular capillary tube : Influence of secondary flows along corners

Institut de Mécanique des Fluides de Toulouse

Abstract

Modelling of evaporation of a pure liquid within a capillary tube of circular cross section is a classic problem which has been the subject of many studies. Here we consider the case of tubes of polygonal cross section. This case leads to quite different results owing to the liquid flow along the tube edges induced by the capillary forces. Experiments performed with tubes of square cross section indicate a much faster evaporation rate compared with tubes of equivalent circular cross section. The exponent in the expression relating the evaporation flux to the elapsed time is different from the classic 1/2. A model of evaporation in tubes of square cross section is proposed. It is shown that different solutions are possible depending on the competition between capillary, gravity and viscous effects. The case of dominant capillary effects is discussed in more details.