Drag reducers, also known as drag reducing agents (DRA) and flow improvers, are any material that reduces frictional pressure loss during fluid flow in a conduit or pipeline. Pressure loss reduction is achieved by reducing the level of turbulent motion in the flow. Using DRA allows increased flow using the same amount of energy or decreased pressure drop for the same flow rate of fluid in pipelines. The current class of DRA, consisting of long-chain hydrocarbon polymers that act as turbulence inhibitors along the pipe wall to decrease the amount of energy lost in turbulent activity.
Frictional pressure drop, or drag, is a result of the resistance encountered by flowing fluid coming into contact with the pipe wall. There are generally two types of flow – laminar and turbulent. The friction pressures observed in laminar flow cannot be changed unless the physical properties of the fluid are changed. The current class of DRA does not change fluid properties and hence is effective only in turbulent flow. In most petroleum pipelines, the liquid flows through the pipeline in a turbulent
regime. Therefore, current DRA can perform very well in most pipelines.
In a turbulent flow regime, the fluid molecules move in a random manner, causing much of the energy applied to them to be wasted as eddy currents and other indiscriminate motion. DRA works by an interaction of the polymer molecules with the turbulence of the flowing fluid.