COMPARISON of FRICTION FACTOR EQUATIONS FOR NON‐NEWTONIAN FLUIDS IN PIPE FLOW1

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Abstract
The pressure drop, due to friction, in pipe flow of non‐Newtonian fluids can be estimated if the friction factor is known. For laminar flow, the friction factor for power law, Bingham plastic and Herschel‐Bulkely fluids can be obtained from a single theoretical relationship. However, a number of different relationships have been developed for turbulent flow. This paper presents a summary and comparison of these relationships. Friction factor predictions were found to differ significantly depending on the flow behavior index, Reynolds number and Hedstrom number. Generally, the spread of predictions increased as the fluid deviated from Newtonian behavior. Significant errors can be made when using relationships based on fluids without a yield stress to predict friction factors for fluids having a yield stress.