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Predictions of Heat Transfer and Pressure Drops in Heat Exchanger Ducts with lndustrial Fluids
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English
Abstract
Central to the problem of heat exchangers design is the prediction of pressure drop and heat transfer in the exchanger passages. In order to make such predictions for non-Newtonian fluids, it is necessary to know the relation between the viscous properties of the fluid and the wall shear rate. This is done by assuming a constitutive equation which relates the local apparent viscosity of the fluid to the local shear rate. An often used constitutive equation because of its simplicity is the power law equation which however is only valid for particular fluids over a limited wall shear rate (or duct Reynolds number) range.
This study concerns the limits of applicability of the power law equation. The method involves a considerations of a more general equation which has power law and Newtonian behavior as asymptotes. The more general equation contains an operating and property parameter whose values specify the operating shear rate range and thus the appropriate viscous properties. It is concluded that using the power law equation outside of its applicability range can lead to serious errors in predicting the pressure drop and heat transfer. This conclusion is illustrated by specific examples for both forced and free convection in heat exchanger ducts (Brewster and Irvine [1], Irvine [2]).
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Authors
Citation
Lee, D. and Irvine, T., "Predictions of Heat Transfer and Pressure Drops in Heat Exchanger Ducts with lndustrial Fluids," SAE Technical Paper 970937, 1997, https://doi.org/10.4271/970937.Also In
References
- Brewster, R. A. Irvine, T. F. Jr. 1987 “Similitude Consideration in Laminar Flow of Modified Power Law Fluids in Circular Ducts,” Warme Stoffubertragung 21 83 86
- Irvine, T. F. Jr. Wu, K. C. 1982 “Vertical Channel Free Convection With a Power Law Fluid,” The American Society of Mechanical Engineers Paper 8 2-W A/HT-69
- Dunleavy, J. E. Middleman, S. 1966 “Relation of Shear Behavior of Solutions of Polyisobutylene,” Trans. Soc. Rheol. 10 151 168
- Irvine, T. F. Jr. Kim, S. C. Gui, F. L. 1988 “Graetz Problem Solutions for a Modified Power Law Fluid,” Symposium on Fundamentals of Forced Convection Heat Transfer ASME 101 123 127
- Shah, R. K. London, A. L. 1978 “Laminar Flow Forced Convection in Ducts” Supplement No. 1, Advances in Heat Transfer Academic Press