ABSTRACT
The ow of liquid in a conduit, such as a pipeline, results in frictional energy losses. As a result of this energy loss, the pressure of the liquid in the conduit decreases along the conduit in the direction of the ow. For a conduit of xed diameter, this pressure drop increases with increasing ow rate. The effect of a drag reducer added to a liquid is to reduce the frictional resistance in turbulent ow (Reynold’s number greater than about 2100) compared with that of the pure liquid. This is sometimes called the Toms effect after the inventor of the denition.131 Drag-reducing agents (DRAs) are sometimes known as friction reducers or ow improvers, although the latter term can be confused with wax inhibitors/pour-point depressants such as poly(meth)acrylic esters. DRAs interact with the turbulent ow processes and reduce frictional pressure losses such that the pressure drop for a given ow rate is less, or the ow rate for a given pressure drop is greater. In most petroleum pipelines, the liquid ows through the pipeline in a turbulent regime. Therefore, DRAs can perform very well in most pipelines. Because DRAs reduce frictional energy losses, increase in the ow capability of pipelines, hoses, and other conduits in which liquids ow can be achieved. DRAs can also decrease the cost of pumping uids, the cost of equipment used to pump uids, and provide for the use of a smaller pipe diameter for a given ow capacity. As crude oil is cooled to near its pour point, the effectiveness of DRAs may be reduced. The largest use of oil-soluble DRAs is for pipeline transportation of rened oils, not crude oils.
