Noncircular Passages

R. G. Deissler, and M. F. Taylor, Analysis of Turbulent Flow and Heat Transfer in Noncircular Passages, NASA TR-31, 1959. 

A variety of noncircular passage geometries, including the rectangular duct, have been utilized for internal flow applications, for example in compact heat exchangers and solar collectors. The study of the hydrodynamic behavior in a rectangular duct requires a two-dimensional... 

Various investigators have studied in-tube condensation in noncircular passages. Fieg and Roetzel [121] and Chen and Yang [160] analyzed condensation inside elliptical tubes. Kaushik and Azer [161] established an experimental correlation for internally finned tubes. Lee et al. [162] experimentally studied condensation of R-113 within an internally finned tube and a spirally twisted tube and compared performance to that of a smooth tube. Using a modified form of the correlation of Cavallini and Zecchin [148] (Eq. 14.138) ... 

Equation 17.87 is accurate within 2 percent [46]. The transition flow/data for noncircular passages are rather sparse Eq. 17.87 may be used to obtain fair estimates of/for noncircular flow passages (having no sharp corners) using the hydraulic diameter as the characteristic dimension. 

Turbulent Flow. A compendium of available / and Nu correlations for circular and noncircular flow passages are presented in Ref. 46. Table 17.16 is condensed from Ref. 46, summarizing the most accurate / and Nu correlations for smooth circular and noncircular passages. 

A careful observation of accurate experimental friction factors for all noncircular smooth ducts reveals that ducts with laminar/Re < 16 have turbulent/factors lower than those for the circular tube, whereas ducts with laminar/Re > 16 have turbulent/factors higher than those for the circular tube [48], Similar trends are observed for the Nusselt numbers. If one is satisfied within 15 percent accuracy, Eqs. 17.87 and 17.88 for/and Nu can be used for noncircular passages with the hydraulic diameter as the characteristic length in / Nu, and Re otherwise, refer to Table 17.16 for more accurate results for turbulent flow. 

Obot NT (1988) Determination of incompressible flow friction in smooth circular and noncircular passages. A generalized approach including validation of the century old hydraulic diameter concept. Trans ASME J Fluid Eng 110 431 0... 

E. R. G. Eckert, and T. F. Irvine Jr., Flow in Corners of Passages with Noncircular Cross Sections, Trans ASME, (78) 709-718,1956. 

It is generally accepted that the hydraulic diameter correlates Nu and /for fully developed turbulent flow in circular and noncircular ducts. This is true for the results accurate to within 15 percent for most noncircular ducts. Exceptions are for those having sharp-angled corners in the flow passage or concentric annuli with inner wall heating. In these cases, Nu and /could be lower than 15 percent compared to the circular tube values. Table 17.16 can be used for more accurate correlations of Nu and /for noncircular ducts. 

Diameter of spherical particle Average diameter of the particle Sieve passage diameter for 85% of the particles Sieve passage diameter for 50% of the particles Hydraulic diameter of a noncircular flow Inner diameter of pipe... 

---