Dittus-Boelter relation

E. For heating and cooling turbulent gases and other low viscosity fluids at DG/p > 8,000 the Dittus-Boelter relation is used. See Figures 10-46, 10-51, and 10-52. 

When a liquid is forced through a channel or over a surface maintained at a temperature greater than the saturation temperature of the liquid, forced-convection boiling may result. For forced-convection boiling in smooth tubes Rohsenow and Griffith [6] recommended that the forced-convection effect be computed with the Dittus-Boelter relation of Chap. 6 [Eq. (6-4)] and that this effect be added to the boiling heat flux computed from Eq. (9-33). Thus... 

For the empty tube the heat transfer coefficient can be estimated by the traditional correlations. If d is the diameter of the pipe, the Nusselt number Ud/k is commonly related to the Prandtl and Reynolds numbers by the Dittus-Boelter relation... 

The procedure of taking a ratio of two coefficients, as done in equations (91) and (92), using a Dittus-Boelter equation for the hypothetical liquid-only case, leads to the relation ... 

Several methods of computing an analytical Reynolds number for the two-phase flow were tried. The fluid properties were evaluated at various temperatures including wall, film and average bulk conditions. Both gaseous and two-phase densities were related to the above temperatures. These Reynolds numbers along with corresponding Prandtl numbers were used in calculating an estimated Nusselt number by the Dittus-Boelter equation. 

For fully developed mrbulent flow in smooth mbes, Dittus and Boelter have recommended the following relation ... 

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