Evaporation of Sessile Droplet on Porous Membrane under varying Airflow

The evaporation of sessile droplets is a complex yet fundamentally important process in fluid dynamics, with applications ranging from microfluidics and heat transfer to inkjet printing and biomedical diagnostics. In this study, we experimentally investigate the influence of airflow rate on the evaporation dynamics of a sessile droplet placed on porous membranes. A custom-built experimental platform featuring a 3D-printed airflow box, precision flowmeters, manometers, and thermocouples was developed to enable controlled airflow beneath the membrane. High-resolution imaging, coupled with ImageJ and OpenDrop analysis, was used to monitor temporal changes in droplet diameter, contact angle, and volume. Experiments were conducted at five different flow rates (1, 1.5, 2, 2.5, and 3 SCFM) under consistent ambient temperature and humidity conditions. The diameter and contact angle evolution revealed a transition from constant contact radius (CCR) evaporation mode in early stages to a mixed mode in the later phases. With increasing flow rate, a marked acceleration in evaporation rate was observed, corresponding to enhanced convective heat and mass transfer mechanisms. At 3 SCFM, evaporation was completed in less than half the time required at 1 SCFM, underscoring the strong dependence of droplet lifetime on airflow intensity. Moreover, the evolution of droplet volume over time exhibited an almost linear decay, indicating a 1–1 power law behaviour. The study deepens fundamental understandings of sessile droplet evaporation kinetics and membrane-assisted processes, evaporative cooling, and energy-efficient thermal systems.