Simulation of multicomponent aerosol dynamics

Author: Kim, Yong Pyo

Year: 1992

Degree: Dissertation (Ph.D.)

Advisor: Seinfeld, John H.

Committee Members: Seinfeld, John H.; Gavalas, George R.; Flagan, Richard C.; Okuyama, Kikuo

Option: Chemical Engineering

DOI: 10.7907/SE1X-K706

Abstract

Chemical composition and, therefore, several physical properties, such as refractive index or density, of an aerosol system may be distributed in one particle size. The effect of these particles of the same size but different properties, so-called mixed particles, on aerosol dynamics can be important. Several aspects of the number-property distribution; effect on aerosol dynamics and importance, definition, state of the art of the measurement technique, available data, and numerical schemes are discussed and further research directions are discussed.

The moving sectional method is extended to simulate multicomponent aerosol dynamics resulting from condensation/evaporation processes. This method uses a Lagrangian approach in which section boundaries and component masses in a section vary according to the characteristics of condensation/evaporation rates while conserving number concentration in a section throughout the simulation. Simulation of model problems for which new analytical solutions have been obtained shows excellent agreement with the analytical solutions. Limitations and applicability of the sectional method are discussed.

A technique for direct numerical solution of the multicomponent aerosol general dynamic equation is developed and tested. The method obtains the aerosol size-composition distribution without the need to make any a priori assumptions about the nature of the distribution. Numerical solutions are compared with analytical solutions for model problems of pure condensation/evaporation, pure coagulation, and simultaneous condensation and coagulation. The advantages, applicability, and the limitations of the approach are discussed.

An analysis of the tandem differential mobility analyzer (TDMA) is proposed in which the conditioner between the two DMAs is simulated by the multicomponent aerosol general dynamic equation (GDE). The use of the TDMA to separate an externally mixed aerosol is illustrated by simulating the data of Liu et al. (1978).

Numerical issues in grid-based photochemical air quality models are reviewed. Numerical schemes for advection and chemical kinetics in gas-phase and for dynamics in aerosol-phase are compared.

Finally, a numerical code is developed based on direct numerical solution of the multicomponent aerosol general dynamic equation.

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