Evaporation and condensation of multicomponent electronic cigarette droplets and conventional cigarette smoke particles in an idealized G3–G6 triple bifurcating unit

•We developed and validated a novel improved CF-PD model for simulating multicomponent electronic cigarette (EC) droplet-vapor aerosols with interactions.•Parametric analyses on the evaporation/condensation behaviors of EC-droplets vs. conventional cigarette smoke particles (CSPs) in still air and G3–G6 triple bifurcating unit (TBU) are discussed.•Ambient RH, initial droplet diameter, and initial water mass fraction are the dominant parameters that can influence the droplet-growth ratio.•Hygroscopic growth of droplets will influence their deposition patterns by enhancing the inertial impaction and limiting the Brownian motions.

The present research study is intended to provide fundamental understanding of the dynamics and transport of aerosols from an e-cigarette in an idealized tubular G3–G6 respiratory tract model. A computational model has been developed that includes the effects of hygroscopic growth as well as evaporation from multicomponent aerosol droplets. The aerosols investigated usually contain carrier solvents such as propylene glycol (PG) and glycerol, along with water, nicotine, and flavors. An experimentally validated computational fluid-particle dynamics (CF-PD) model is presented, which for the first time is capable of simultaneously simulating interactive, multicomponent droplet-vapor dynamics with evaporation and/or condensation. As a first step to accomplish such complex numerical simulations, an idealized G3–G6 triple bifurcating unit (TBU) has been selected. The results are compared with the conventional smoke particles (CSPs) as well as solid particles. Parametric analysis and comparisons of the evaporation/condensation dynamics for EC-droplets vs. cigarette smoke particles were performed, including the effects of different droplet initial diameter, composition, temperature, and ambient relative humidity. The results indicate that EC-droplets, being more hygroscopic than cigarette smoke particles, tend to grow larger in maximum size in a typically highly humid environment. Additionally, a correlation for the growth ratio of EC-droplets in TBUs is proposed.