Design and modeling of a thin water falling-film for convection-cloud chambers

Document Type

Article

Publication Date

1-16-2026

Abstract

Convection–cloud chambers offer a controlled environment to study aerosol-cloud interactions. Ensuring sustained supersaturation in these chambers requires a reliable and efficient water sourcing mechanism. Maintaining saturated boundary conditions on side-walls is important in chambers with large vertical dimensions (up to 10m) aimed at achieving collisional growth of cloud droplets. This study introduces the design, modeling, and measurement of a falling-film system capable of maintaining a stable, continuously replenished water film for continuous evaporation. A distributor is tested, ensuring uniform water coverage over a panel with a range of surface treatments. These surface treatments with micron to 100micron-scale roughness allow for film stability over vertical lengths greater than 1 m. A film thickness equation is derived to show the relaxation and mass flux characteristics of the film as it flows down the panel. This model is used to evaluate the feasibility of a thin-film evaporator for water sourcing in a tall convection–cloud chamber. A scalar flux model adapted from previous chamber studies is implemented to assess supersaturation and water sourcing constraints. Experimental measurements include qualitative and quantitative assessments of the thin film’s performance and thickness. Results indicate that the distributor can maintain a continuous laminar film over time scales of days, for a range of flow rates sufficiently large to avoid complete evaporation on distances of more than 10m. These findings confirm the feasibility of a thin-film evaporator as a water source for maintaining supersaturated conditions in convection–cloud chambers.

Publication Title

Measurement Science and Technology

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