Viscous drag os disc pump:
Fig. 2-15. The concept behind the disc pump is over 100 years old.Nicola Tesla, the genius who invented the alternating current motor and generator, invented and patented the first practical working model of the pump in 1913.Inspite of the many advantages demonstrated for this concept, the disc pump remained a mere curiosity until the “drag” concept was reexamined and reintroduced in the mid-seventies.A disc, or drag, turbine was developed, but was dropped for technical reasons.The disc pump, however, as developed by Max Gurth, appearrd to be a technically feasible, as well as a useful, concept.The theory of operation incorporates two obscure but salient principles of fluid mechanics-boundary layer and viscous drag.These phenomena occur simultaneously whenever a surface is moved through a fluid.The boundary layer phenomenon occurs in the disc pump when fluid molecules “lock” onto or embed on the surface roughness of the disc rotors.A dynamic force field is developed, which produces a strong radially accelerating friction force gradient whithin and between the molecules of the fluid and the discs, creating a boundary layer effect.The resulting frictional resistance force field between the interacting elements and the natural predilection of fluids to resist separation of its own continuum, creates the “adhesion” phenomenon known as viscous drag.These effects, acting together, are the prime movers in transferring the necessary tangential and centrifugal forces to propel the fluid with increasing momentum toward the discharge outlet at the periphery of the discs.
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Advantages claimed for this pump are mininum wear with abrasive materials, gentle handling of delicate fluids, ability to easily handle highly viscous of heavily loaded fluids, and freedom from vapor lock.Disc type pumps are manufactured by Disco Flow as well as by U.S. Pump and Turbine in Paramount, California.