Evaluation of an Environmental Reaction Chamber

Abstract

A cylindrical, Pyrex glass chamber with stable temperature control was evaluated to determine the residence time of aerosol particles within an enclosure, and to compare our results to the theoretical expression derived by Crump and Seinfeld (1981). Monodisperse polystyrene latex particles with diameters between 0.04 and 3 μm were used to determine the particle deposition rates under different water temperature gradients (δT_w) between the top and bottom water layers of the chamber. The water layers and an insulating fiberglass jacket around the side wall helped to maintain a steady temperature gradient in the chamber and this was found to be very important in controlling particle deposition. Results indicated that the minimal deposition losses occurred at δT_w = 0°C for particles between 0.2 and 0.3 μm, with a residence time as long as 38 h. Results also showed that particle deposition rate can be described by the theory of Crump and Seinfeld with an exponent n = 2.02 and a turbulence intensity k _e = 0.0039/s at δT_w = 0°C, and n = 2.04 and k _e = 0.020/s at δT_w = 10°C gradient. Preliminary results also indicated that a slightly higher temperature at the bottom of the chamber (e.g., δT_w = 5°C for 0.62-μm particles) might induce an upward thermophoretic force which would reduce particle settling.