FILLMORE

Many processes and technological systems use falling liquid films to enhance heat and mass transfers. This strategy is, for instance implemented in evaporative cooling towers, absorption and distillation processes, carbon capture, desalination, or cooling systems for electric mobility. Thin liquid films usually flow over complex surfaces, characterized by the presence and repetition of geometrical features such as corrugations, slits, or perforation. Since the pioneering work of Nusselt and Kapitza, liquid film flows have been the subject of an extensive literature, with the reference configuration being the vertical or inclined flat plate. Yet, there is much less studies on the interactions between liquid films and surface features, and they mostly consider the effect of corrugations on the dynamics of falling films. The FILLMORE project aims at increasing the knowledge, understanding, and control of the interactions between liquid films and surface features, by examining how these interactions appear at different space scales, to optimize the transfer and propose more appropriate solutions to achieve better efficiency, lower energy consumption, and environmental footprint. If the macroscale strongly depends on the multi-physics process or the system studied, the mesoscale and the microscale have a generic character. The project is therefore based on the study of generic geometries representative of the structures encountered in different industrial sectors. These geometries are selected to focus on the effect of surface wettability and topographies on liquid film flows. They are simplified to allow well-controlled experiments and well-defined simulations. The first objective is to produce comprehensive and detailed experimental data at the microscale and mesoscale; the flows on these elementary geometries will be carefully characterized (flow pattern, film thickness maps, velocity field, and flow rate transferred by the perforations). In particular, a new 3D3C velocimetry method requiring only one camera will be implemented. The second objective is to extend this set of data with micro-resolved, high-fidelity, numerical simulations (CFD), with careful validation of the interface tracking and triple line dynamics method. The third objective is to develop appropriate mesoscale models (Saint-Venant models averaged over film thickness) based on these experimental and numerical data. The fourth objective is to optimize the geometry of the patterns, using simulations of representative industrial systems, where liquid films falling on complex geometries are encountered, simultaneously with other physico-chemical phenomena driven by hydrodynamics, such as interfacial heat and mass transfer or chemical reaction on surfaces; aiming at proposition innovative concepts (geometrical elements, fluid supply strategy...) using these numerical tools. These approaches will be applied to two real cases: the optimization of cooling towers to minimize fouling while guaranteeing cooling efficiency, and the direct cooling for electrical motors.