A detailed review and analysis of the hydrodynamic characteristics of laminar developing and fully developed flow in non-circular ducts is presented. New models are proposed which simplify the prediction of the friction factor Reynolds product fRe for developing and fully developed flow in most non-circular duct geometries found in heat exchanger applications. By means of scaling analysis it is shown that complete problem may be easily analyzed by combining the asymptotic results for the short and long duct. Through the introduction of a new characteristic length scale, the square root of cross-sectional area, the effect of duct shape has been minimized. The new model has an accuracy of ± 10 percent or better for most common duct shapes. Both singly and doubly connected ducts are considered.
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