Nusselt Numbers for Tubes of Various Cross-Sections

In the intermediate domain (2200 Re 4000) at moderate Prandtl numbers, the Nusselt number can be estimated using the formula [254] 

For the entry region of the tube in the case of simultaneous development of the hydrodynamic and thermal boundary layers, the local Nusselt number Nu = Nu(2Q at constant temperature or heat flux at the wall can be calculated from the formulas [267] 

More detailed information about heat and mass transfer in turbulent flows through a circular tube or plane channel, as well as various relations for determining the temperature profile and Nusselt (Sherwood) numbers, and other useful information can be found in the references [ 185, 289, 406, 427, 457], which contain extensive literature surveys. 

Limit Nusselt Numbers for Tbbes of Various Cross-Section 

Heat exchange in fully developed laminar flow of fluids in tubes of various cross-sections was studied in many papers (e.g., see [80, 253, 341]). In what follows, we present some definitive results for the limit Nusselt numbers corresponding to the region of heat stabilization in the flow in the case of high Peclet numbers (when the molecular heat transfer can be neglected). 

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