Churchill correlation, friction

This correlation is valid for 0 < Pr < 10 and for 0 < Re < 10 , therefore, considering that inside l.C. engine exhaust systems the Prandtl number is usually lower than 1 and Re is that typical of fully turbulent flow regimes, this correlation can be applied to the study of exhaust gas flows. The friction coefficient / that appears in Eq. (17.10) is given by the Churchill correlation as well [16] ... 

Currently the standard TRACE code heat transfer (Dittus-Boelter) and fluid pressure drop (Churchill and Moody) correlations are applied to the gas cooler. Use of the Churchill correlation and Moody curves, and mathematical representations of the curves, for calculation of the single-phase friction factor in a variety of flow-channel geometries is a common engineering practice. Information on the TRACE default correlations is available in the TRACE theory manual (Reference 12-9). A surface roughness of 2E-6 m is used with the TRACE single phase friction correlations. In order to match the HB24 pressure drop prediction, additional frictional flow factors are included in the hydraulic model. The TRACE model also includes plenums to provide a location to specify form loss factors for the gas cooler. The heat transfer and pressure drop correlations would have been updated as the cooler design was determined and as test data was collected. 

Introducing the general correlation for the friction factor suggested by Churchill (11), figure 2 shows how the choking conditions now depend on the pipe length for isothermal conditions and variable friction factor. As it is seen, the effect of the variable friction factor is negligible. 

The friction frictor can now be calculated witii the help of one of tiie numerotis correlations known from process engineering, e.g. the correlation by Churchill... 

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