ARTICLE:

• A METHOD TO DETERMINE HEAT TRANSFER OF STREAMLINED TUBE BUNDLES  download article

J. Davidson
University of Minnesota, Minneapolis, USA

Z. Li
University of Minnesota, Minneapolis, USA

S. Mantell
University of Minnesota, Minneapolis, USA

ABSTRACT

Streamlined tubes with elliptical, lenticular and teardrop outer profiles have been proposed for use in polymer heat exchangers to reduce drag and to increase the surface area for heat transfer. The streamlined tubes are designed with nonuniform wall thickness to avoid mechanical failure and deformation. In the present study, a dimensionless parameter termed the tube efficiency is introduced to facilitate an engineering estimate of overall heat transfer rate of such tubes. The tube efficiency is defined as the ratio of the actual heat transfer of the tube to that of an idealized tube with zero conductive resistance. It is shown that the tube efficiency depends on the Biot number and three length ratios: the minor-to-major axis ratios of the outer and inner surface, and the wall thickness-to-semi-minor axis ratio of the outer surface. Tube efficiency, determined from numerical solution of the two-dimensional conduction equation, is presented in graphical format for elliptical, lenticular and teardrop tubes with inner and outer minor-to-major axis ratio of 0.3, 0.5 and 0.8 and Biot numbers from 0 to 10. The results are interpreted to determine the circumstances under which streamlined tubes enhance heat transfer compared to circular tubes.

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