From Single Drop to Falling Film. An Insight Into the Hydrodynamic and Geometry of a Falling Water Film Under Elevated Pressure of Carbon Dioxide

摘要

A better design of process engineering plants with respect to heat and mass transfer can be achieved by improving the understanding of wettability of liquids on solid surfaces. In this study an attempt was made to measure the wettability of a single liquid drop on a horizontal surface under elevated pressure of carbon dioxide. A comparison with calculated contact angles can be made only if the so called interaction parameter is able to describe the relation between cohesion in the bulk phases and adhesion between the phases at the given conditions. In case of dynamic wetting of a falling film the forces of gravity, buoyancy and shear stress on the free surface area should be considered along with the wetting phenomena. Assuming that the cross sectional area of the falling film normal to its flowing direction has the geometry of a circular segment, the triple line contact angle of the film can be obtained by measuring the thickness and the width of the film. This value can be compared with the contact angle value of a sessile drop. Furthermore several approaches were made to calculate the velocity profile in this cross sectional area. A comparison between the obtained mean velocity of the falling film and the experimental value was performed.