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强化传热期刊
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ISSN 打印: 1065-5131
ISSN 在线: 1026-5511

强化传热期刊

DOI: 10.1615/JEnhHeatTransf.v1.i2.60
pages 169-178

Performance Comparisons of Enhanced Tubes with Discrete and Wavy Disruption Shapes

B. Arman
Energy Systems Division, Argonne National Laboratory, Argonne, IL. USA 60439-4815
Thomas J. Rabas
Energy Systems Division, Argonne National Laboratory, Argonne, IL USA 60439-4815; Consultant, 1015 Claremont Drive. Downers Grove, IL 60516

ABSTRACT

This paper presents comparisons of the friction factors and heat-transfer coefficients obtained with enhanced tubes with transverse discrete and almost transverse wavy two-dimensional disruptions. Both experimental data and numerical predictions were used for the comparisons. For the latter, a two-layer turbulence model incorporated in a body-fitted, finite-volume method was used.
The disruption shape, discrete or wavy, depends on the manufacturing process. If an extrusion process is used, discrete disruptions (ribs) of various profiles are obtained that are separated from each other by a flat or unaltered inside diameter. If a spirally indenting process is used, a wavy profile is obtained with a continuously varying inside diameter between two adjacent disruption peaks. These disruptions are almost transverse to the tube axis and separated by a distance that exceeds the reattachment length.
Based on these comparisons, the following conclusions are obtained: (1) the disruption shape is not an important correlating parameter for discrete disruptions, (2) only the friction factor is influenced by the shape for wavy disruptions, and (3) there are major differences between both the friction-factor and heat-transfer performance of discrete and wavy disruptions with the same maximum disruption height and spacing. However, the most important finding is that the groove radius of spirally indented tubes should be increased because there is a substantial reduction of the friction factor but only a small decrease in the thermal performance. Additional comparisons of predicted results were made to obtain a fundamental understanding of the influence of these different shapes.


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