Non-Newtonian fluids: Frictional pressure loss prediction for fully-developed flow in straight pipes
Abstract
ESDU 91025 discusses models used to describe the rheology of time independent pseudohomogeneous non-Newtonian fluids (power-law, Bingham, Herschel-Bulkley and a generalized model due to Metzner and Reed); they are used to calculate the laminar flow pressure drop (which is independent of pipe roughness in this regime). Values of a generalized Reynolds number are suggested to define transitional and turbulent flow. For turbulent flow in smooth pipes, pressure loss is estimated on the basis of an experimentally determined rheogram using either the Dodge-Metzner or Bowen approach depending on the available measurements. Bowen requires results for at least two pipe diameters. The choice of Dodge-Metzner when data are limited is discussed; seven possible methods are assessed against five sets of experimental results drawn from the literature. No method is given for transitional flow, which it is suggested should be avoided, but the turbulent correlation is recommended because it will yield an overestimate. Suggestions are made for the treatment of roughness effects. Several worked examples illustrate the use of the methods and a flowchart guides the user through the process from experimentally characterizing the behavior of the fluid to determining the pressure drop. A computer program, ESDUpac A9125, is also provided.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- October 1991
- Bibcode:
- 1991STIN...9216261.
- Keywords:
-
- Computer Programs;
- Friction Factor;
- Laminar Flow;
- Nonnewtonian Fluids;
- Pipe Flow;
- Pressure Reduction;
- Turbulent Flow;
- Reynolds Number;
- Rheology;
- Turbulence;
- Fluid Mechanics and Heat Transfer