AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Experimental and Computational Fluid Dynamics Study of Nucleation in a Flow Reactor: Sulfuric Acid with Ammonia and Trimethylamine
IMANUEL BIER, David Hanson, Coty Jen, Peter H. McMurry, Augsburg College
Abstract Number: 344 Working Group: Aerosol Chemistry
Abstract Nucleation of particles with sulfuric acid, water, ammonia (NH$_3), and trimethylamine was studied in a flow reactor and also simulated with computational fluid dynamics. Nucleation was quantified experimentally using a DEG-SMPS and computationally via a combination of computational fluid dynamics and the kinetic formation and decomposition of small clusters of sulfuric acid and base molecules. Base nucleation capabilities of sulfuric acid with NH$_3 and/or trimethylamine were simulated to predict particle concentrations at the given flow reactor conditions. The thermodynamics of the acid-base nucleating system were adjusted until the predicted particle concentrations agreed with the measured concentrations. Temperature and relative humidity dependencies were also explored experimentally and computationally. Comparisons of the energy of the acid-base clusters derived here with those of recent quantum chemical calculations show an overall agreement but some quantitative differences stand out. The thermodynamics determined in the computational fluid dynamics methods facilitate the comparison of results of experiments of widely disparate conditions. Also, measurements show that the presence of NH$_3 significantly enhances particle formation rates in the sulfuric acid-trimethylamine system. Potential mechanisms for this synergistic effect will be presented.