FLOW-DEPENDENCE OF THE CASELLA RESPIRABLE-DUST CYCLONE*

Publisher Website
Google Scholar
Abstract
The penetration characteristic of the Casella respirable-dust cyclone was examined at flow-rates of 1.9 l min −1 , 1.4 l min −1 and 0.9 l min −1 . The cyclone and a non-selective sampler were exposed to coal-dust clouds, and the size distributions of the samples were measured by Coulter analysis. A cascade impactor was used to relate the Coulter (equivalent spherical) diameter to aerodynamic diameter. The results confirmed that the penetration characteristic of the cyclone at its recommended flow-rate (1.9 l min −1 ) matches the MRC respirable-fraction definition and showed that a square-law characteristic applies also at the other flow-rates. The cut-off diameter, at which penetration is zero, was inversely proportional to (flow-rate) 0.7 , a finding consistent with measurements on other small cyclones. It follows that the penetration characteristic is relatively insensitive to error in setting flow-rate, but, on the other hand, deliberately varying the flow-rate cannot give much detailed information on aerodynamic diameter distribution. The mass fraction of the cloud in particles of aerodynamic diameter < 3.5 μm can, however, be estimated roughly by comparing simultaneous measurements at 0.9 l min −1 and 1.9 l min −1 . The work also confirmed that the average equivalent spherical diameter of coal particles is close to their average aerodynamic diameter, and confirmed recent work on sampler entry efficency in calm air.

This publication has 1 reference indexed in Scilit: