The effect of preceding elbows on aerosol deposition in subsequent flow elements

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references (leaves 19-20).Issued also on microfiche from Lange Micrographics.The wall losses in tubing elements due to the secondary flows established in an elbow were experimentally determined. Monodisperse, liquid aerosol particles of sizes 5-20 []m were used to perform the tests. The tests were conducted at Reynolds number in laminar, transition, and turbulent regimes. 17 mm (0.68 in) and 11 mm (0.43 in) tubing were used to perform the tests and the Stokes number was varied by changing the particle size. Initial calibration tests were performed at a Reynolds numbers greater than 10,000. Tests were conducted using 11 mm in tubes at Reynolds number ranging from 1,750 to 9,500. The penetration through the straight tube having an upstream elbow was 15% to 20% less than that through tubes without the upstream elbows, for small lengths of straight tube. In tube lengths of more than 50 diameters, the penetration with an upstream bend was more than that without a bend. This effect was Reynolds number dependent and was noticed only at turbulent Reynolds numbers. Plots of penetration and L/D[t] were used to compare the straight tube deposition with and without an upstream bend in the transport system. Deposition velocities were calculated from the penetration values and were used to develop a correlation. The effect of the curvature ratio of the upstream elbow on the penetration through the straight tube was also studied keeping the Reynolds number and Stokes number constant. The curvature ratio seemed to have little or no effect on the deposition of particles on the downstream tubing elements. Tests were conducted with two elbows in series of U and S configuration, to study the effect of first elbow on penetration through the second elbow. A wide range of Reynolds numbers and Stokes numbers were used and a correlation was developed using the 3D curve of penetration versus the Reynolds number and Stokes number. Additional tests were conducted to study the effect of elbows in series (U and S configuration) on the penetration through straight tubes downstream of the elbows. Plots of penetration versus L/Dt were used to compare the straight tube deposition with and without preceding elbows in a series