Seminars

ME/IE 8773-8774
THERMODYNAMICS AND HEAT TRANSFER SERIES (1130 ME)
Topic: Heat Transfer and the Environment
Host: David B. Kittelson

Enhanced Coagulation Due to Evaporation and Van der Waals Forces and
its Effect on Nanoparticle Evolution

by

Mark Z. Jacobson
Associate Professor
Environmental Fluid Mechanics and Hydrology
Department of Civil & Environmental Engineering
Terman Engineering Center, Room M-31
Stanford University, Stanford, CA 94305-4020

Wednesday, March 2, 2005
3:30-5:00 p.m.
Room 1130 ME
Coffee and cookies will be available at 3:15 p.m. in Room 1130 ME before the seminar

Abstract: Aerosol particles affect human, animal, plant, and microorganism health, visibility, building appearance, cloud formation, and regional and global climate. In particular, the radiative effects of particles are affected by their mixing state and size. Field data have shown that the size distribution and mixing state of emitted particles evolve substantially within a few hundred meters of emission. Here, several factors not previously accounted for in three-dimensional model calculations of particle evolution are discussed. These include the enhancement of Brownian coagulation due to (1) Van der Waals forces offset by viscous forces, (2) evaporation of semivolatile compounds, and (3) fractal geometry. For example, the evaporation of semivolatile organic compounds (<C24) from a particle is demonstrated to enhance the particle's rate of coagulation, and this appears important, along with the other factors, in helping to explain particle evolution near a roadway measured by two datasets, including one developed by D.B. Kittelson and W.F. Watts at the University of Minnesota. Neither condensation, complete evaporation, coagulation alone, nor preferential small-particle dilution explains the evolution. The finding may apply universally to combustion sources emitting semivolatile compounds. Other factors affecting particle evolution will also be discussed.

Bio: — Mark Jacobson is an Associate Professor of Civil and Environmental Engineering at Stanford University. He has been on the faculty at Stanford since 1994. Goals of his research are to improve our understanding of physical, chemical, and dynamical processes in the atmosphere through numerical modeling, to improve the simulation of air pollution, weather, and climate, and to understand better the relationship between energy use and climate. His degrees are in Civil Engineering (B.S. with distinction, 1988, Stanford), Economics (B.A. with distinction, 1988, Stanford), Environmental Engineering (M.S., 1988, Stanford), Atmospheric Sciences (M.S., 1991, UCLA), and Atmospheric Sciences (Ph.D., 1994, UCLA). To date, he has published two textbooks, "Fundamentals of Atmospheric Modeling" and "Atmospheric Pollution: History, Science, and Regulation," and over 60 peer-reviewed journal articles. He has also developed computer algorithms that are used by hundreds of researchers in the field. He recently received the 2005 American Meteorological Society Henry G. Houghton Award for "significant contributions to modeling aerosol chemistry and to understanding the role of soot and other carbon particles on climate."

Informal Faculty Luncheon: Wednesday, March 2, 2005, 12:00 noon. Meet in 1100 ME and walk to lunch with other faculty. Prof. Mark Jacobson will be able to attend.