Abstract
Abstract. Oxidation flow reactors (OFRs) have been developed to achieve high degrees of oxidant exposures over relatively short space times (defined as the ratio of reactor volume to the volumetric flow rate). While, due to their increased use, attention has been paid to their ability to replicate realistic tropospheric reactions by modeling the chemistry inside the reactor, there is a desire to customize flow patterns. This work demonstrates the importance of decoupling tracer signal of the reactor from that of the tubing when experimentally obtaining these flow patterns. We modeled the residence time distributions (RTDs) inside the Washington University Potential Aerosol Mass (WU-PAM) reactor, an OFR, for a simple set of configurations by applying the tank-in-series (TIS) model, a one-parameter model, to a deconvolution algorithm. The value of the parameter, N, is close to unity for every case except one having the highest space time. Combined, the results suggest that volumetric flow rate affects mixing patterns more than use of our internals. We selected results from the simplest case, at 78 s space time with one inlet and one outlet, absent of baffles and spargers, and compared the experimental F curve to that of a computational fluid dynamics (CFD) simulation. The F curves, which represent the cumulative time spent in the reactor by flowing material, match reasonably well. We value that the use of a small aspect ratio reactor such as the WU-PAM reduces wall interactions; however sudden apertures introduce disturbances in the flow, and suggest applying the methodology of tracer testing described in this work to investigate RTDs in OFRs to observe the effect of modified inlets, outlets and use of internals prior to application (e.g., field deployment vs. laboratory study).
Highlights
Tubular reactors were first introduced to the field of atmospheric science by means of small flow cell reactors developed to study the kinetics of stratospheric reactions (Brune et al, 1983; Howard, 1979; Keyser, 1980; Lamb et al, 1983)
The discovery of secondary processes preceding aerosol formation led to significant emphasis on the study of secondary organic aerosol (SOA) formation (Haagen-Smit, 1952, 1963, 1970; Went, 1960)
The main mathematical descriptors of a fluid element residing in a chamber are its probability distribution function (PDF) and its cumulative distribution function (CDF)
Summary
Tubular reactors were first introduced to the field of atmospheric science by means of small flow cell reactors developed to study the kinetics of stratospheric reactions (Brune et al, 1983; Howard, 1979; Keyser, 1980; Lamb et al, 1983). Accurate kinetic measurements were possible due to the high pipe aspect ratios, which encouraged a high degree of plug flow behavior (Keyser, 1984). The design of these miniature tubular reactors, with volumes on the order of a few cm, was different from that of significantly larger, batch-type or semi-continuous type well-mixed reactors, with volumes on the order of several m3, built to understand aerosol formation in the troposphere (Crump et al, 1982; Crump and Seinfeld, 1980; Leone et al, 1985). It was convenient to mimic the troposphere by treating it as an enormous, well-mixed reactor, which led to the development of larger well-mixed reactors.
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