Rough annulus pressure drop—interpretation of experiments and recalculation for square ribs

A method is presented which allows the interpretation of pressure drop measurements with rough tubes, annuli and parallel plates. A parameter deduced describes the effect of roughness on a turbulent velocity profile. As a result, experimental data with various roughnesses and channel geometries can be generalized and made comparable. The paper summarizes the results of the interpretation of data with rectangular cross section roughnesses given by numerous authors in the literature.

Finally, examples of the recalculation of friction factors are shown, provided that Reynolds numbers of the flow, channel and roughness geometries are given. The results prove that the method proposed enables us to calculate friction factors of isothermal turbulent flow in concentric annuli with rough inner tubes with a precision which is sufficient for design problems.