Experimental and numerical studies of aerosol penetration through screens

摘要

This research reports the results of experimental and numerical studies performed to characterize aerosol deposition on four different types of commercially available screens (electroformed-wire, woven-wire, welded-wire, and perforated-sheet) over a wide range of Stokes numbers (Stk ~ 0.08 to 20) and Reynolds numbers (ReC ~ 0.5 to 575). The objective of the present research was to use the results of the study to develop models and data that will allow users to predict aerosol deposition on screens. Three-dimensional Computational Fluid Dynamics (CFD) simulations using Fluent (version 6.1.22), as a tool, were undertaken and thus validating the numerical technique and then the result has been compared with the experimental data. For each type of screen, results showed that beginning at critical value of Stokes number where efficiency increased gradually to its maximum value that was almost asymptotic to the areal solidity. It is shown that data obtained from experimental and numerical studies for one particular type of screen would collapse to a single curve if the collection efficiency is expressed in terms of non-dimensional parameters. Correlations characterizing the aerosol deposition process on different types of screens were developed based on the above methodology. The utility of the developed procedure was demonstrated by considering an arbitrary test case, for a particular condition and reconstructing the efficiency curve for the test case. Further, results of the current study were compared with earlier researchers? models (Landahl and Hermann, 1949; Davies, 1952; Suneja and Lee, 1974; Schweers et al., 1994) developed for aerosol deposition on fibrous filters and discussed. These results suggest that the aerosol collection characteristic on different models is different and depends on the nature of the manufacturing process for a typical model (wire or fiber). Finally, the pressure coefficient (Cp) for flow across the screen can be expressed as a function of the Reynolds number (ReC,f) and the fraction of open area (fOA). Correlations expressing the actual relationships were evolved. Additionally, a model was developed to relate pressure coefficient in terms of correction factor (OAfg) and Reynolds number.