2000 Progress Report: Development of a Novel Condensation Nuclei Counter and Application to Ultrafine Particle FormationEPA Grant Number: R826654
Title: Development of a Novel Condensation Nuclei Counter and Application to Ultrafine Particle Formation
Investigators: Hopke, Philip K. , Mavliev, Rashid , Wang, Hwa-Chi
Current Investigators: Hopke, Philip K. , Lee, Doh-Won , Mavliev, Rashid , Smoridin, Vladimir , Wang, Hwa-Chi
Institution: Clarkson College , Illinois Institute of Technology
EPA Project Officer: Shapiro, Paul
Project Period: October 1, 1998 through September 30, 2001
Project Period Covered by this Report: October 1, 1999 through September 30, 2000
Project Amount: $393,657
RFA: Exploratory Research - Environmental Chemistry (1998) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Sustainability , Land and Waste Management , Air , Engineering and Environmental Chemistry
The objectives of this research project are to: (1) develop an improved condensation nuclei counter to measure the nucleation of model compounds onto charged particles of various kinds to examine the relationship between molecular properties of the working fluid and the particles; and (2) develop models correlating the chemical properties of the fluid, particles, and ions with their nucleation activities.
Initial experiments were conducted using the original turbulent mixing CNC system (Mavliev and Wang, 2000; Mavliev, et al., 2001). Supersaturation was controlled by means of changing the DBP vapor pressure in nozzle flow by saturating only a predetermined part of the flow while the total flow and temperature remain constant. This approach allows changing the initial DBP vapor pressure while keeping the flow structure and temperature field unchanged. The DBP concentration in the outlet of the vapor generator was measured experimentally for different ratios of saturated and bypass flows and found to be close to estimated values. Experimental results for transitions from heterogeneous nucleation to homogeneous nucleation are presented for NaCl and WOx particles at various DBP vapor pressures. With increasing of the DBP vapor pressure, the concentration of enlarged particles increases until it reaches a plateau. At higher initial values of DBP pressure, homogeneous nucleation prevails and the number concentration of particles follows a curve typical for homogeneous nucleation recorded in the absence of nuclei. Nuclei with different mobility diameters were activated at different values of vapor pressure. There are significant differences in the slopes of particle activation curves for NaCl and WOx particles. The reasons for such differences are a subject for the continuing research of this project and studies continue at this time. These results have been presented by Mavliev, et al. (2001). This work largely completes the work on the nucleation of dibutylphthalate on various substrates.
A new and improved turbulent mixing CNC has been designed, constructed, and studied. We made side-by-side tests of two identical units to ensure that the parallel measurements made at IIT and Clarkson would be comparable. We have begun to make a series of measurements of nucleation of additional vapor compounds on a series of different composition nuclei. Nucleation for all of the vapors have been measured for NaCl and silver particles. The work on carbon and H2SO4 is continuing. These results have prompted some limited additional studies on related solid substrates such as KCl and Na2SO4.
|Vapor Substance||Nuclei Substance|
We have experimentally measured the contact angle for most of the combinations of the vapor compounds on the various substrates. These data will be useful in interpreting the results of the nucleation measurements.
At this time, we are continuing the detailed set of measurements involving the various types of particles with the various fluids. At this time, Dr. Mavliev is leaving as a full time participant in our project to take a position in industry. He will continue to assist us in the interpretation of the data. We thus will be terminating the subcontract to IIT after November 6, 2000. We are likely to use the resulting funds to hire a short term visitor who could assist us in the evaluation and interpretation of the data. We will be writing a number of additional papers based on the work that has already been completed and more results are anticipated.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
|Other project views:||All 20 publications||8 publications in selected types||All 8 journal articles|
||Mavliev R, Wang H-C. Design and performance characteristics of a turbulent mixing condensation nuclei counter. Journal of Aerosol Science 2000;31(8):933-944.||
||Mavliev R, Hopke PK, Wang H-C, Lee D-W. A transition from heterogeneous to homogeneous nucleation in the turbulent mixing CNC. Aerosol Science and Technology 2001,35(1):586-595.||