Pumps/pumping turbulent flow problems

Johnson (1982) reviewed some of the problems of pumping non-Newtonian mixtures. In his assessment of fittings for sewage, he indicated important discrepancies in the laminar regime with losses 2-4 times as much as those for water flows. In the turbulent regime, the losses were either of the order of those for water or higher. He recommended that further studies be conducted for laminar flow, but for turbulent flows, the concept of equivalent length be used. 

Installations that have sharp turns, shut-off, flow-control valves, or undersized pipe on the suction-side of the pump are prone to chronic performance problems. Such deviations from good engineering practices result in turbulent suction flow and cause hydraulic instability that severely restricts pump performance. 

This type of damage is dealt with comprehensively in Section 8.8. It can be particularly severe in seawater giving rise to cavitation corrosion or cavitation erosion mechanisms, and hence can be a considerable problem in marine and offshore engineering. Components that may suffer in this way include the suction faces of propellers, the suction areas of pump impellers and casings, diffusers, shaft brackets, rudders and diesel-engine cylinder liners. There is also evidence that cavitation conditions can develop in seawater, drilling mud and produced oil/gas waterlines with turbulent high rates of flow. 

Mold cooling or temperature control is typically done with a thermolator that pumps water, water and ethylene glycol mixtime, or oil through channels in the mold to heat or cool the plastic. Heat transfer (usually cooling) problems develop if corrosion or deposits accumulate in the channels (water lines) in the mold. Other issues are that water lines are not drilled uniformly around the part, coolant lines are not routed correctly, or coolant flow is not tin-bulent. Flow turbulence is defined by a Reynolds number of 3500 or greater and is difficult to achieve in some plants because of inadequate feed and retirni line size or restrictions in the tools cooling... 

Hydraulic study of the cold plenum. For the cold plenum, hydraulic studies are particularly focused on the problems of supply to the primary pumps. For these to function correctly the supply should be homogeneous [8.18, 8.22]. Moreover, knowledge of the velocity field in the cold plenum is used to validate calculations. In hydraulic studies of this type, flow is similar if the Reynolds number is respected. In the reactor flows are fully turbulent, and flows obtained in scale models are accepted as being representative of reality as long as they are also fully turbulent. For practical reasons tests are carried out on scale models with Reynolds numbers > S.IO. ... 

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