AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
On Passive Temperature Control and the Internal DMA Temperature in Hygroscopicity Tandem Differential Mobility Analyzers
CHRISTOPHER OXFORD, Brent Williams, Washington University in St. Louis
Abstract Number: 622 Working Group: Instrumentation and Methods
Abstract Two temperature control methods have been developed to limit the error in Hygroscopicity Tandem Differential Mobility Analyzers (H-TDMAs): active control and passive control (Swietlicki et al. 2008). In active control, H-TDMAs control both temperature and relative humidity in the second Differential Mobility Analyzer (DMA2). Since DMA2 and the measurement devices exist within the temperature-controlled volume, the measured relative humidity and temperature are equal to the relative humidity and temperature inside DMA2. In passive control, rules are used to distinguish accurate scans. These rules, based on measures of temperature and relative humidity, cull the results to achieve an acceptable error.
Active control has two error reduction advantages over passive control. Active control reduces temperature differences between DMA2 and the measurement devices and reduces temperature gradients within DMA2. In passive control, temperature gradients within DMA2 are present, and temperature/relative humidity differences between DMA2 and the measurement devices exist. Both active control benefits help increase the accuracy in H-TDMA measurements.
In this study, we placed a Resistance Temperature Device (RTD) inside DMA2 and measured the internal and external DMA2 temperature while measuring ammonium sulfate growth factors. The H-TDMA and the measurement devices were exposed to laboratory conditions, and heat transfer with laboratory air was encouraged using a box fan set to high. We compare the error due to the inference of DMA2 internal conditions with the remaining error (including DMA2 temperature gradients) to determine the primary benefit to active control. Additionally, we recommend new passive control rules for laboratory experiments.