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Particulate Fouling of Water in Internal Helical-rib Roughness Tubes

Wei Li
Engineered Air, 32050 W. 83rd St, Desoto, KS 66018

Ralph L. Webb
Department of Mechanical Engineering The Pennsylvania State University, University Park, PA 16802, USA

Arthur E. Bergles
Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York; University of Maryland, College Park, Maryland; Massachusetts Institute of Technology, Cambridge, Massachusetts, USA

Abstract

This paper provides accelerated particulate fouling data in five 15.54 mm ID. copper, helically ribbed tubes taken at low water velocity (1.07 m/s, Re = 16,000, ppm = 1300). The ranges of geometric parameters were number of rib starts (18 to 45), helix angle (25 to 45-deg), and height (0.33 to 0.55 mm). Aluminum oxide particles with 3.0 µm average particle diameters were used as foulant. These geometries provide a new class of internal enhancement that is typical of commercially enhanced tubes presently used in water chillers. There are two factors to decide the ratio of the enhanced-to-plain tube fouling factor: a fouling process index and an efficiency index. A semi-theoretical fouling correlation as a function of the efficiency index was developed. The new theory of dividing a fouling factor ratio into only two factors significantly simplifies the fouling analysis.

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