Modeling aerosol dynamics of cigarette smoke in a denuder tube

- Aerosol dynamics model: coagulation, heat/vapor transfer, phase transition, deposition.
- Simulation of vapor phase nicotine deposition in a denuder tube.
- Model features fixed size bins each containing a dynamic uniform particle distribution.
- Particles act as vapor sources/sinks at certain distances from denuder tube inlet.
- Model suggests nicotine protonation higher than 75% to explain experimental data.

A new aerosol dynamics model, ADiC (Aerosol Dynamics in Containments), was developed, which considers the effects of coagulation, heat and vapor transfer, phase transition and deposition of particles. The particle size distribution is represented by individual uniform distributions situated in a fixed size grid. That way numerical diffusion is avoided and quasi-simultaneous simulation of coagulation and growth processes is possible. Due to the complexity of the computer model, partial model validation was performed by testing the individual sub-models against the existing experimental evidence.The ADiC model was used to simulate the aerosol dynamics of freshly generated cigarette smoke in acid-covered denuder tubes. Modeling results were compared to data from several studies that report nicotine deposition rates. Simulations revealed that several parameters with large uncertainties can potentially have great effects on the nicotine deposition rate. A nicotine protonation interval from 75% to 90% of the nicotine mass initially on the particle fits the experimental data well in the posterior tube sections. For the anterior tube sections, however, a steady increase of nicotine protonation by roughly 15% is required. Loss of water in denuder tubes has not been documented in the experimental studies found in the literature. Increased deposition rates by a factor up to 7 have been simulated in case of the denuder tube being a perfect sink for water. A simplified sub-model describing diffusion limited phase transition showed a considerable effect on total nicotine deposition of the order of 10% and more for experimentally determined viscosity values. Temperature differences between the tube wall and the aerosol have a considerable, however timely very limited, effect on deposition rate.Several poorly quantified processes and parameters have been discussed and simulated with respect to their potential to affect nicotine deposition rate in a denuder tube. While some of them are difficult to measure (e.g. nicotine protonation, diffusion limited transport within particles), others (e.g. water deposition within the denuder tube) can easily be determined. Thus, the ADiC model can be used, apart from evaluating experimental data, as a tool to plan and design experimental setups.