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PROJECT CHARGE: 1702 PROJECT TITLE: Filtration Physics PROJECT LEADER: R. W. Dwyer PERIOD COVERED: July 1 - 31, 1981 DATE OF REPORT: August 7, 1981 The effects of cigarette-smoke baffles on subjective response are being investigated. Cigarettes having ten millimeter hollow tubes at the mouth end have been submitted to Flavor Development for testing. Cambridge 85 cigarettes with bypass channels, and samples with smoke-stream dispersing and collimating baffles have also been submitted for evaluation. Subjective analysis indicates that the smoke-expanding.baffles gave rise to "increased smoke volume and full- ness", while those collimating the.smoke were characterized as having "decreased flavor and smoke volume" compared to control Cambridge samples. Baffles are also being employed in a rod/baffle/filter configuration. for studying filter efficiency/RTD effects(1). Stable aerosols of dibutyl phthalate are being used to calibrate our particle sizing equipment. The aerosol-is produced by a Monodisperse Aerosol Generator and characterized with a Light Scattering Photometer (LSP). The LSP works well with stable aerosols, but due to its relatively long measuring cycle, it cannot be used with cigarette smoke. A Multiple Wavelength Light Extinction Photo- meter (MWLEP), however, is capable of continuously monitoring the extinction of light by aerosols. Such an instrument has been constructed in our lab, and is our prime candidate for determining the particle size distributions of fresh cigarette smoke. Computer programs have been written to calculate the best particle size distribution based on extinction measurements. Preliminary cali- bration runs, in which the LSP and MWLEP instruments were charged with a variety of sizes of- monodisperse aerosols, showed excellent agreement between their respective size measurements(2,3,4,5,6). Support was given to the Development Smoke Studies Project in operating and' calibrating the Sidestream Visibility Monitor (SVM). The sidestream sampling chamber and the extinction cell were redesigned in an effort to improve the flow of the smoke through the system(7). Based on experimental results, a semi-empirical equation has been derived which relates CA filtration efficiencies to basic physical parameters of the tow. This study has been expanded to include the effects of vapor condensation and filter fiber shapes on TPH efficiencies(8). The aerosol coagulation study is continuing. The coagulation.rate constant has been found to be time dependent in both the free molecular and continuum regimes. In both regions, account must be taken of the time necessary for the colliding particles to establish a steady-state concentration gradient. The rate constants evaluated at the zero time limit in the free molecular regime and the infinite time limit in the continuum regime show good agreement with the corresponding values from the literature(5). RWD/mmn References: 1. M. L. Fleming 5. K. A. Cox 2. D. M. Puzio 6. R. W. Dwyer 3. R. M. Creamer 7. D. D. McRae 4. T. Hylton 8. S. G. Abel QW~~Wyg,