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TECHNICAL BRIEFS

Calcium Carbonate Formation on Cross-Linked Polyethylene (PEX) and Polypropylene Random Copolymer (PP-r)

[+] Author and Article Information
Patricia Sanft

Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave., S.E., Minneapolis, MN 55455

Lorraine F. Francis1

Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave., S.E., Minneapolis, MN 55455lfrancis@umn.edu

Jane H. Davidson

Department of Mechanical Engineering, University of Minnesota, 111 Church St., S.E., Minneapolis, MN 55455

1

Corresponding author.

J. Sol. Energy Eng 128(2), 251-254 (Jun 22, 2005) (4 pages) doi:10.1115/1.2189863 History: Received May 26, 2005; Revised June 22, 2005

The accumulation of calcium carbonate (referred to as scale) on the surface of cross-linked polyethylene and polypropylene random copolymer tubes is compared to that on copper. Water with total calcium and carbonate concentration of 3×103M and a pH of approximately 9.1, yielding a supersaturation of 7.8, was pumped through the tubes at a velocity of 0.07ms for 2.5, 5, and 7.5h. Flow was laminar with Reynolds numbers of <1000. Sections of the tubes were analyzed at the designated time points to determine the extent of scaling. Results include scanning electron microscope images of the tube surfaces before and after exposure to the supersaturated water and chemical analysis to determine the mass of calcium carbonate per unit surface area. Measured scaling rates of the two polymer tubes are similar to that of copper.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 1

Schematic of the system to study calcium carbonate formation on PEX, PP-r, and copper tubes

Grahic Jump Location
Figure 2

SEM images at 250× of Cu, PEX, and PP-r tubes after exposure to laminar flow of supersaturated water at S=7.8: (a) Cu after 2.5hr, (b) Cu after 5hr, (c) Cu after 7.5hr, (d) PEX after 2.5hr, (e) PEX after 5hr, (f) PEX after 7.5hr, (g) PP-r after 2.5hr, (h) PP-r after 5hr, (i) PP-r after 7.5hr

Grahic Jump Location
Figure 3

Mass of calcium carbonate deposited per unit area of tube versus time

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