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].