Coagulation and Surface Losses in Disperse Systems in Still and Turbulent Air

Abstract

Smoke chamber studies have been made of the ageing of ammonium chloride smokes under various controlled degrees of turbulent air motion as well as in still air. The changes in mass concentration and particle number were followed for 5.5 hr. under each set of conditions, and some data on particle size distribution were obtained. The logarithm of the mass concentration was found to vary linearly with time under all conditions. None of the particle number data lent themselves to interpretation on the basis adopted by previous workers. They were described quantitatively by equations developed from general postulates which take into account loss to various surfaces. The equations permitted analytical separation of coagulation and surface effects, and the constant descriptive of the latter was closely related to that associated with mass loss. The coagulation constant for still air was found to be only slightly greater than the ideal Smoluchowski value. A description was obtained of the manner in which the various constants increased with the degree of air motion.

The Effect of Relative Humidity on Coagulation and Surface Losses of Ammonium Chloride Smoke

“…I t has been shown previously (3,4) that experimental data obtained a t relative humidities of 15% to 30% are adequately described by equations based on quite general grounds, i.e., For personal use only.…”

“…Estimates of the apparent particle size distribution of selected thermal precipitator samples were made with the aid of a Patterson-Cawood graticule in some experiments. The details of all sampling and assessment techniques have been described elsewhere (3,4).…”

“…T h e smolte was produced by heating 108 mgm. of ammonium chloride in an external generator as described previously (3,4). In general, particle number and surface loss measurements were made periodically for about 100 min., but in two experiments the former were continued for more than four hours.…”

“…I t is possible, however, to determine these separate effects by analysis of appropriate particle number and surface loss data. A suitable analytic procedure and experimental confirmation of it have been described in detail (3,4) in connection with studies of the aging of ammonium chloride smoke under normal laboratory humidity conditions (at Ralston, 15% t o 30% R.H.). This article describes studies with ammonium chloride smoke a t various relative humidities ranging from 15% to 98y0, leading t o a description of the effect of water vapor on the coagulation and surface loss processes.…”

An industry-scale modeling for the turbulence agglomeration of fine particles

“…In addition, measurements of aerosol coalescence on Earth are influenced by coupled effects of Brownian motion, turbulent shear and acceleration, and gravitational settling, making the experiment design difficult. Some attempts focused on measuring the coagulation rate of solid aerosol particles, in stirred tanks 32,33 or in a turbulent pipe flow. 34 In these studies, coagulation effects are observed by measuring the decay of the aerosol number density once the turbulent flow is initiated.…”