Accurate Measurements and Simulations of the Evaporation and Trajectories of Individual Solution Droplets

Abstract

A refined numerical model for the evaporation and transport of droplets of binary solutions is introduced. Benchmarking is performed against other models found in the literature and experimental measurements of both electrodynamically trapped and freefalling droplets. The model presented represents the microphysical behavior of solutions droplets in the continuum and transition regimes, accounting for the unique hygroscopic behavior of different solutions, including the Fuchs–Sutugin and Cunningham slip correction factors, and accounting for the Kelvin effect. Simulations of pure water evaporation are experimentally validated for temperatures between 290 K and 298 K and between relative humidity values of approximately 0% and 85%. Measurements and simulations of the spatial trajectories and evaporative behavior of aqueous sodium chloride droplets are compared for relative humidity values between 0 and 40%. Simulations are shown to represent experimental data within experimental uncertainty in initial conditions. Calculations of a time-dependent Péclet number, including the temperature dependence of solute diffusion, are related to morphologies of sodium chloride particles dried at different rates. For sodium chloride solutions, dried particles are composed of collections of reproducibly shaped crystals, with higher evaporation rates resulting in higher numbers of crystals, which are smaller.

Effect of the Addition of Diblock Copolymer Nanoparticles on the Evaporation Kinetics and Final Particle Morphology for Drying Aqueous Aerosol Droplets

“…SADKAT is a free-to-use and open-source program that enables the calculation of complete droplet trajectories and evaporation profiles. Since it has been discussed in detail in previous publications, this program is only briefly reviewed here. , …”

“…Since it has been discussed in detail in previous publications, this program is only briefly reviewed here. 17,42 Evaporation and condensation processes for droplets containing one volatile component and one involatile component can be accurately modeled using SADKAT, which accounts for both the solute effect and surface curvature. 43 SADKAT was designed to be applied to droplets in the continuum regime (droplet diameters > 1 μm) but includes correction factors to allow an accurate simulation of smaller droplets.…”

“…At lower evaporation rates (smaller Pe), each droplet remains wellmixed as it dries, resulting in the formation of single crystal particles. 16,17 Droplets with insoluble inclusions form a surface layer of densely packed nanoparticles as they dry; this initial layer is denoted the nanoparticle shell. 18 The Pe of the drying droplet influences the radius and thickness of this shell.…”

“…Rapid surface enrichment results in multiple nucleation sites, which form multiple small crystals that undergo coalescence. At lower evaporation rates (smaller Pe ), each droplet remains well-mixed as it dries, resulting in the formation of single crystal particles. , …”

Dependence on relative humidity in the formation of reactive oxygen species in water droplets

“…Analysis of the dynamics of influenza and COVID-19 across seasons clearly shows that the quantity of virus shed is significantly higher during winter and rarer in the summertime. Considering that people in temperate regions spend more than 80% of their time indoors, regardless of external weather conditions ( 10 , 13 – 15 ), it is reasonable to anticipate that the majority of respiratory infections would occur in these indoor settings ( 16 ), where iRH levels can easily drop below 40% ( 8 , 10 , 17 – 22 ). Climate data for COVID-19 transmission were collected from the outdoor environment to inform spreading distancing guideline and prevent COVID-19 transmission.…”