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Corresponding Author

Rabie, Lotfi

Subject Area

Mechanical Power Engineering

Article Type

Original Study

Abstract

This work presents an experimental study for the effect of drag reducing polymer additives upon a water flow in nozzles and diffusers. Five circular nozzles and diffusers of constant area ratio of 4 and half angle α = 4o ,6o , 10o, and 12o respectively are used. Two polymer types; Polyox coagulant and polyacrylamide are used at different concentrations. The results show that both polyacrylamide and polyox have no effect on the flow through nozzles at any flow rate and polyner concentrations. However, for diffuser flow, polymer additives results in a substantial increase in the pressure recovery of the diffuser. This effect increases with the flow rate and polymer concentration up to 10 wppm. For higher concentrations as 50 wppm, the effect is complicated and more interesting especially with polyacrylamide additives. The pressure recovery of the diffuser begins to decrease at some value of the flow rate. The decrease becomes more pronounced as the diffuser half angle increases. This is thought to be due to the increase of the viscoelastic properties with con centration and the elongation strains with the flow rate and diffuser half angle. The results also show that the pressure recovery increases with the diffuser half angle. They also show that polymer effect starts at a certain flow rate similar to the onset of drag reduction in pipe flow.

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