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International Heat Transfer Conference 7

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

MODELING ASSUMPTIONS FOR TURBULENT HEAT TRANSFER

M. Jischa
University Essen; Technical University Clausthal, Clausthal-Zellerfeld, FRG

H. B. Rieke
University Essen

DOI: 10.1615/IHTC7.1810
pages 257-262

Abstract

In order to improve existing modeling assumptions for the turbulent heat transfer we start with the transport equation for the Reynolds heat flux. We neglect the convective and diffusive terms. This is approximately valid for boundary layer type flow not too far from equilibrium. In connection with Prandtl's well known k-model, our modeling assumptions lead to a simple algebraic formula Prt = K1 + K2/(Pr Rem) for the turbulent Prandtl number which agrees very well with known experiments. Based on this expression, the Reynolds heat flux, the thermal diffusivity, and the temperature profiles are determined for a fully developed turbulent tube flow with constant heat transfer rate. Finally, the Nusselt number is calculated and compared with empirical relationships as well as measurements. Our numerical results for the Nusselt number are approximated by a simple formula Nu = A + B (Pr Re)n.

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