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Thermal Sciences 2004. Proceedings of the ASME - ZSIS International Thermal Science Seminar II
June, 13-16, 2004, Bled, Slovenia

DOI: 10.1615/ICHMT.2004.IntThermSciSemin


ISBN Print: 978-9-61913-930-1

Compound Heat Transfer Enhancement - Performance Characteristics of Some "Rough Surfaces" with Twisted Tape Inserts

pages 975-982
DOI: 10.1615/ICHMT.2004.IntThermSciSemin.1240
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RESUMO

One of the most promising heat transfer enhancement techniques is the compound augmentation method, in which different enhancement techniques are used simultaneously. This study compares the characteristics of some passive compound techniques for single phase flow studied up to now: rough tube (sand-grain roughness) with twisted tape insert; internally grooved rough tube with twisted tape and corrugated tube combined with twisted insert. The performance characteristics of these combinations of "rough" surfaces and twisted tape inserts have been assessed using extended performance evaluation criteria. The goal is to evaluate the influence of the characteristic parameters of the tubes: height-to-diameter ratio e/D, relative pitch p/e, relative helix angle β* and others, and the relative pitch of the twisted tape H/D on the thermodynamic efficiency. The benefit of replacing the smooth tubes in shell-and-tube heat exchangers for different practical applications have been evaluated and the thermodynamic optimum has been defined by the minimization the entropy generation number compared with the relative increase of the heat transfer rate or relative reduction of the heat transfer area.

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