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Design and Characterization of a New OFR: The Particle Formation Accelerator (PFA)
NINGJIN XU, Don Collins, University of California, Riverside
Abstract Number: 249
Working Group: Instrumentation and Methods
Abstract
Oxidation flow reactors (OFRs) are valuable tools for studying the formation and evolution of secondary aerosol (SA) in the atmosphere. Here we present a new all-Teflon reactor, the Particle Formation Accelerator (PFA), that was designed, constructed, and characterized through both experimental measurements and CFD modeling. We describe some of the design elements that were used to reduce flow recirculation and gas and particle losses and wall interactions. We report laboratory characterization of the reactor, including hydroxyl radical production, UV intensity distribution, residence time distributions (RTDs) for gases and particles determined using both computational simulation and experimental verification, gas and particle losses, and a comparison of aerosol yields of α-pinene and m-xylene with those reported in the literature. By wrapping the reactor with highly UV-reflective material, an overall UV intensity comparable to that in other OFRs is achieved using a relatively low power output lamp. Near laminar flow velocity profiles of gases and particles are suggested by CFD simulations and confirmed by the RTD experimental results. The transmission efficiencies of non-reactive gases and of particles are greater than 90%. Particle loss was reduced by minimizing static charge on the Teflon surfaces, resulting in higher inferred aerosol yields of α-pinene and m-xylene. Preliminary measurements of SA production when sampling ambient air in Riverside, CA, U.S. showed that the mass concentration of SA formed in the reactor was up to 1.8 times the mass concentration of the ambient aerosol at the same time. In the future, we will focus our efforts on measurement of the composition of the particulate and gaseous products during one or more field studies to evaluate how well the PFA reactor simulates atmospheric chemistry that typically requires hours or days.