Glycerol and propylene glycol nucleation in a laminar flow diffusion chamber

Homogeneous nucleation enables aerosol generation from supersaturated vapors. Despite extensive vapor-phase nucleation research, quantitative data on nucleation rates for specific substances and their mixtures remain limited. This study investigates the homogeneous nucleation of glycerol and propylene glycol using a laminar flow diffusion chamber at three saturator temperatures. Experimental nucleation rates were derived from the measured particle concentrations and normalized using computational fluid dynamics modeling based on the classical nucleation theory. Simulations were employed to resolve temperature and saturation ratio profiles, enabling accurate reconstruction of nucleation isotherms. Findings agree with prior diffusion cloud chamber studies and were further evaluated using Hale plot scaling. Results show that the nucleation of propylene glycol occurs at significantly lower supersaturation and smaller temperature gradients between the saturator and condenser compared to glycerol. Critical cluster sizes were determined both from the Kelvin equation and from the slopes of nucleation isotherms, revealing that glycerol forms smaller critical clusters (0.72-0.97 nm) than propylene glycol (1.3-1.5 nm). These findings align with previously reported results obtained using diffusion cloud chambers and confirm the influence of molecular structure on nucleation behavior. This study provides valuable insight into the fundamental nucleation mechanisms of polyhydroxylated compounds and supports the design and optimization of aerosol-forming processes in practical applications.