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RESEARCH PAPERS: Forced Convection

Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes: Part II—Transition and Turbulent Flows

[+] Author and Article Information
R. M. Manglik, A. E. Bergles

Heat Transfer Laboratory, Rensselaer Polytechnic Institute, Troy, NY 12180-3590

J. Heat Transfer 115(4), 890-896 (Nov 01, 1993) (7 pages) doi:10.1115/1.2911384 History: Received July 01, 1992; Revised March 01, 1993; Online May 23, 2008

Abstract

Thermal-hydraulic design correlations are developed to predict isothermal f and Nu for in-tube, turbulent flows with twisted-tape inserts. Experimental data taken for water and ethylene glycol, with y = 3.0, 4.5, and 6.0, are analyzed, and various mechanisms attributed to twisted tapes are identified. Tube blockage and tape-induced vortex mixing are the dominant phenomena that result in increased heat transfer and pressure drop; for loose- to snug-fitting tapes, the fin effects are insignificant. The limiting case of a straight tape insert correlates with the hydraulic-diameter-based smooth tube equation. Tape twist effects are thus isolated by normalizing the data with the asymptotic predictions for y = ∞ , and the swirl effects are found to correlate with Re and l/y . The validity of the final correlations is verified by comparing the predictions with previously published data, which include both gases and liquids, under heating and cooling conditions and a wide range of tape geometries, thereby establishing a very generalized applicability. Finally, correlations for laminar (presented in the companion Part I paper) and turbulent flows are combined into single, continuous equations. For isothermal f , the correlation describes most of the available data for laminar-transition-turbulent flows within ±10 percent. For Nu, however, a family of curves is needed due to the nonunique nature of laminar-turbulent transition.

Copyright © 1993 by The American Society of Mechanical Engineers
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