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ISSN Online: 2377-424X

ISBN Print: 0-89116-130-9

International Heat Transfer Conference 6
August, 7-11, 1978, Toronto, Canada

SCALE PREVENTION BY ANNULAR FLOW OF AN IMMISCIBLE LIQUID ALONG THE WALLS OF A HEATED TUBE

Get access (open in a dialog) DOI: 10.1615/IHTC6.1900
pages 391-396

Abstract

This study examines the possibility of preventing scale deposition from an aqueous solution flowing inside a heated tube, by covering the tube surface with an annular film of kerosene. The scaling characteristics, in single phase flow, of the solutions tested are also described.

The profiles of scale deposits formed during con-centration of Na2S04 solutions differ markedly, depending on whether the solution is circulated in a closed or an open circuit. The initial deposit formed promotes turbulence in the sublaminar layer thereby augmenting the initial overall heat transfer coefficient by as much as 35%.

It is demonstrated that scale deposition may be completely prevented, provided stable annular flow can be ensured. This requires the use of a viscous oil in the case of a concentrated Na2S04 solution, thus imposing a marked thermal resistance penalty. However, in the case of water, stable annular flow of kerosene can be readily ensured and CaS04 and CaCOз deposit formations are found to be completely prevented under severe scaling conditions.