Factors affecting condensate drainage from inclined subcooled rough plates

Surface roughness plays an important role in dictating the mode of condensation on a subcooled surface, as it directly influences the condensate accumulation and drainage. While wettable surfaces mostly facilitate filmwise condensation, non-wettable surfaces render dropwise condensation. For both types of condensation, condensate drainage and detachment from the condenser surface plays a pivotal role in dictating the condensation heat transfer coefficient. We performed experiments on stainless-steel surfaces (hydrophilic) with different degrees of topological roughness. We altered the angle of inclination (<10^°) and other parameters, such as ambient temperature, relative humidity, etc. to investigate their effect on the condensate drainage from the plate. For a smooth surface, there was no formation of film; however, for rough surfaces under particular conditions, filmwise condensation was observed. For both types of condensation, we report the time and location of gravity-induced detachment of condensate droplets from the plate and identify the influence of the above-mentioned parameters in the dripping phenomenon. Identifying the conditions that encourage dripping from hydrophilic surfaces during condensation has strong relevance in several engineering applications, starting from aerospace engineering to air conditioning and ventilation systems.