3.0 Effect of polymer and surfactant DRAs on pressure drop and friction factor for single phase flows in curved pipes and channels

Majority of reports suggest that the effectiveness of drag-reducing agents is higher in straight pipes than in curved pipes [9], [11], [23]. The reduced drag reduction in curved pipes, compared with straight pipe has been attributed to secondary flow resulting from the centrifugal forces [23]. The lower drag reduction in curved pipes is the result of the differences between the extended laminar and extended turbulent flow friction factor curves which are much larger for straight pipes.

3.1 Effect of polymer and surfactant DRAs on pressure drop for single phase liquid flows in coiled pipes

A number of interesting reports on the application of polymers and surfactants as drag-reducing agents for flow through coils exist in open literature. In general, the effectiveness of polymers and surfactants in reducing pressure loss is dependent on pipe geometry, flow rate as well as type, concentration and molecular weight of the drag-reducing agents. It also depends on temperature, presence of dissolved salts and phase distribution before and after adding the drag-reducing agent [76].