SURFACTANT DRAG REDUCING FLOW

摘要

In the paper drag reduction with surfactant additives and their application in district heating systems is presented. Dilute solutions of certain surfactants affect the flow behavior of fluids in turbulent flow and show a much lower coefficient of friction than does the solvent alone. Surfactants are low molecular chemical substances with a great interfacial activity. At higher concentrations they form aggregates of molecules known as micelles. The superstructures made of associations between rod-like micelles are responsible for drag reduction. Their main effect is to cause a thickening of the buffer layer on account of damping of the turbulent layer. Surfactants have an advantage over the polymer additives as their degradation under the high shear stresses is only temporary. The simulation of possible benefits of surfactant application in new hot water pipe network is done. The hydraulic analysis has shown that the application of surfactants could reduce pressure drops, significantly. Thus, a new district heating network can be designed with smaller pipe diameters, pumps with reduced pump power and decreased pumping energy. Economic benefits of this reductions are considerable.