Abstract:

ESDU 79014 gives curves and equations for the determination of pressure loss due to transverse ribs of various cross-sections, helical threads of various cross- sections, longitudinal or spiral fins, and three-dimensional arrays of hemispherical projections or truncated pyramids. The data apply to circular-section pipes with Newtonian incompressible flow running full but guidance is also given on their application to rectangular or annular cross-section pipes. The data do not apply in high heat transfer rate situations but the effect of the variation of physical properties is taken into account by correction factors. They apply to the turbulent flow regime only, and information on when the flow is turbulent, laminar or in transition between those regions is given. For laminar flow a calculation method gives the friction loss very simply. A flowchart guides the user through the systematic use of the information and comprehensive practical worked examples illustrate its use. ESDU 66027 deals with pressure losses in straight pipes with random roughness, and ESDU 82021 deals with the effect of systematic roughness on heat transfer.