ESDU AERO 00.02.05
Heat transfer under conditions of forced convection for the subsonic turbulent flow of gases in smooth straight ducts of constant cross section.
Abstract:ESDU Aero 00.02.05 provides data derived from correlation of experimental data that apply to conditions of uniform heat flux or uniform wall temperature, but may be used for other boundary conditions provided the heat flux gradient along the pipe divided by the heat flux is very small. They also apply to compressible flow provided the heat transfer coefficient is defined as heat flux divided by the difference between the wall and stagnation temperatures, and may be used with non-circular cross sections by applying the hydraulic diameter concept. A graph plots the variation of Stanton number with Reynolds number (based on pipe diameter) for gases having a Prandtl number of about 0.72 for fully-developed equilibrium flow. The curve agrees with experimental data to within 10 per cent. For gases with Prandtl number significantly different from 0.72 and flows in which Reynolds numbers exceed 20000, a formula is provided. For a thermal entrance region in which the velocity profile is established but the thermal profile is developing, curves give (i) the ratio of the Stanton number to that in fully-developed flow as a function of distance along the duct and (ii) the mean Stanton number over the region from the entrance also as a function of distance along the duct. No guidance can be given for the case when the velocity and thermal profiles are developing together. Finally the effect of variable gas properties is considered and two graphs give for heating the ratios of the local and mean Stanton number to that in fully-developed flow as a function of the ratio of wall to stagnation temperature; for cooling it was found that the curve for fully-developed flow applied. Those curves agree with experimental data to within 15 per cent. Two worked examples illustrate the use of the data.
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