Restriction of evaporation from soil provides a promising scope to minimize evaporation, hence, water level of soil, thereby conserving water resources. Altering soil wettability by inclusion of hydrophobicity could be an effective way to restrict evaporation. In this study, sessile water droplets (4-μL) were evaporated from an artificial soil pore comprised of three beads. In order to compare between the wettability, the soil pore was created with three glass (i.e. hydrophilic) and Teflon (i.e. hydrophobic) 2.38-mm-diameter beads. The distance between the beads were kept constant (i.e. center-to-center spacing of 3.1 mm). Experiments were conducted in an environmental chamber at 20 ^o^C and the effects of two different relative humidities (i.e. 30% and 75%) on evaporation were studied. Evaporation rate was faster (i.e. \~18 minutes and \~47 minutes at 30% and 75% RH) from hydrophilic pores (i.e. glass) than the Teflon one (i.e. \~24 minutes and \~52 minutes at 30% and 75% RH) due to greater air-water contact area. Rupture of the liquid droplet during evaporation was analyzed and predictions were made on rupture based on contact line pinning and depinning, projected surface area just before rupture and pressure difference across liquid-vapor interface. It was observed that, in hydrophilic pore, the liquid droplet was pinned in two beads and the contact line in the other bead continuously decreased by deforming the liquid-vapor interface, though all three contact lines decreased at a marginal rate in hydrophobic pore. For both hydrophilic and hydrophobic pores, approximately 2 mm^2^ projected area of the droplet was predicted just before rupture occurs. Associated pressure difference responsible for rupture was calculated based on the deformation of curvature of liquid-vapor interface.


Contact Line Pinning and Depinning Prior to Rupture of an Evaporating Droplet in a Simulated Soil Pore

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

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