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RESEARCH PAPERS: Forced Convection and Heat Exchangers

Eddy Diffusivity Based Comparisons of Turbulent Prandtl Number for Boundary Layer and Free Jet Flows With Reference to Fluids of Very Low Prandtl Number

[+] Author and Article Information
K. Bremhorst

Department of Mechanical Engineering, The University of Queensland, Queensland 4072 Australia

L. Krebs

Kernforschungszentrum Karlsruhe GmbH, Institut für Angewandte Thermo- und Fluiddynamik, 7500 Karlsruhe 1, Federal Republic of Germany

J. Heat Transfer 115(3), 549-552 (Aug 01, 1993) (4 pages) doi:10.1115/1.2910722 History: Received April 01, 1991; Revised December 01, 1992; Online May 23, 2008

Abstract

It is shown that turbulent Prandtl numbers for turbulent boundary layer and jet flows correlate well if compared on the basis of eddy diffusivity. Experimental data for liquid sodium (Pr= 0.0058) lead to a universal expression relating turbulent Prandtl number to eddy diffusivity of heat with the same expression applying to boundary layer and jet flows. This suggests that the length and velocity scale dependence of the turbulent Prandtl number is associated predominantly with the eddy diffusivity of momentum. Since turbulent flow codes generally include eddy diffusivity of momentum calculations, simple and accurate estimates of eddy diffusivity of heat are possible without reliance on a variety of turbulent Prandtl number functional relationships for prediction of the temperature field. Available results also indicate that turbulent Prandtl number can be set at 0.9–1.0 irrespective of molecular Prandtl number, provided that εM /ν > 3Pr−1 and the structures of the mean temperature gradient and mean shear are similar.

Copyright © 1993 by The American Society of Mechanical Engineers
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