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 (δTw) 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 δTw = 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 ke = 0.0039/s at δTw = 0°C, and n= 2.04 and ke = 0.020/s at δTw = 10°C gradient. Preliminary results also indicated that a slightly higher temperature at the bottom of the chamber (e.g., δTw = 5°C for 0.62-μm particles) might induce an upward thermophoretic force which would reduce particle settling. © 1992 Elseiver Science Publishing Co., Inc.