Design of a Cryogenic Sampler for Gaseous Hydrogen Peroxide in Ambient Air

摘要

This project designed and characterized the performance of a cryogenic sampler for gaseous H sub 2 O sub 2 . In preliminary experiments, 1-cm ID, 30 cm long U-tube in an acetone-dry ice bath achieved complete peroxide collection efficiency (E/sub H2O2/) from prepared air at 50% relative humidity (RH) and 1.5 ppbv H sub 2 O sub 2 . The performance of the U-tube sampler was further evaluated on the basis of water collection efficiency, a criterion which indicates the time required to collect a sample sufficiently large to analyze for H sub 2 O sub 2 . Water collection efficiency (E/sub H2O/) averaged 6.2 +- 2.9%, indicating good reproducibility but a far lower E than observed for H sub 2 O sub 2 , suggesting that the mechanisms for water and peroxide removal in the cryogenic U-tube differ significantly. Water loss as ice crystals in the exit air stream was observed throughout the runs. Additionally, the value of E/sub H2O/ increased with increasing humidity, and decreased with increased run time. A model of heat and mass transfer in the U-tube, based on Kays' transport correlations for developing laminar flow, yielded a reasonable agreement with experimental work. The model also predicts the observed phase change behavior of water in the U-tube, and supports the observed water loss mechanism. (ERA citation 12:035564)