Convective evaporation of vertical films

TL;DR

This paper investigates the evaporation dynamics of vertical hydrogel surfaces, using experiments and models based on natural convection principles, to better understand soap film evaporation and its influencing factors.

Contribution

It introduces an experimental validation of a convection-based model for vertical film evaporation, considering edge effects and providing insights into evaporation scaling laws.

Findings

Good agreement between measurements and the convection model.

Edge effects contribute noticeably when lateral areas are large.

Scaling laws with the Grashof number are confirmed.

Abstract

Motivated by the evaporation of soap films, which has a significant effect on their lifetime, we performed an experimental study on the evaporation of vertical surfaces with model systems based on hydrogels. From the analogy between heat and mass transfer, we adopt a model describing the natural convection in the gas phase due to a density contrast between dry and saturated air. Our measurements show a good agreement with this model, both in terms of scaling law with the Grashof number and in terms of order of magnitude. We discuss the corrections to take into account, notably the contribution of edge effects, which have a small but visible contribution when lateral and bottom surface areas are not negligible compared to the main evaporating surface area.