Correlation for Problems with Two Dimensionless Groups

Data Correlation for Problems with Two Dimensionless Groups 

The chemical engineering processes which can be characterized by two dimensionless groups are important, especially for heat and mass transfer with gaseous media, as shown in Table 6.4. If the phenomenon can be described with two pi terms we have  

Nevertheless, since it is an empirical relationship, we can only conclude that it is valid over the range of O2 dealt with by the experiments. It would be unwise to extrapolate beyond this range since, as illustrated with the dashed lines in the figure, the nature of the phenomenon can dramatically change if the range of O2 is extended. 

For the valid range, we clearly obtain a curve with a break (B), then for each part, we will produce a particularization of the function 1 from the general Oj and O2 relationship. 

The break in the curve can be associated with a fundamental change in the process mechanism (such as, for example a change from laminar to turbulent flow, a change from moderate natural convection to turbulent natural convection, etc.) 

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