Abstract
This research investigated the impact of topographical surface modification on the dynamics of condensation. Samples consisting of control, fixed-pitch, and gradient micropatterned aluminium were fabricated, and a custom sub-sonic wind tunnel apparatus was constructed and validated for spatially uniform laminar flow using boundary layer characterisation techniques. A psychrometric chamber housed the apparatus to ensure precisely controlled moist air conditions.
The apparatus was designed to mount a single sample upright and was fitted with a Peltier-driven cooling system to induce the formation of surface condensation. An optical imaging system was assembled to capture high-resolution surface images from outside the wind tunnel during a period of condensation development, under free and forced convection conditions. An image processing algorithm was tailored to process the raw optical images and generate droplet size distributions and growth curves detailing the evolving droplet population density. Additionally, normal-incidence videos of an entire surface were captured to qualitatively assess the larger-scale condensation behaviour.
The system reliably captured the characteristic three-stage condensation dynamics on the control surface and produced repeatable growth curves that follow the physical structure observed in literature investigations. The system was tested under free convection conditions, and the system’s responsiveness to airflow was validated under forced convection conditions, where the system effectively induced the acceleration of droplet coalescence and droplet shedding under gravity, to be quantified for comparison to control. Condensation testing on the gradient surfaces provided valuable qualitative insights for the influence of topography on droplet behaviour, but the optical complexity of topographical surfaces posed a fundamental challenge to the accurate image segmentation of droplets, limiting the precision of quantitative droplet population assessments on specific regions of these samples.
This work represents a methodological contribution to the field of applying topographical gradients to condensation management, laying the groundwork for advanced investigations into the complex surfaces.