Screw-pumps

There are designs with two to five screws. The two- and three-screw versions are preferred for high-pressure use because of the favorable leak clearances. 

Remark Without installed compression rate and in case of an almost leakproof conveying chamber, even shortly before the opening of the discharge side the pressure inside the chamber would be almost the same as the suction pressure. 

If the chamber on the discharge side was opened, the gas would stream back into the conveying chamber and would all at once compress the gas at discharge pressure level. This would frequently involve loud noise but also certain harmful thermal effects. 

This planar simplification of a stationary screw with rotating barrel is not unreasonable, provided that the depth of the screw channel is small compared with the barrel diameter. The distribution of centrifugal forces will, of course, 

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Screw Pumps A modification of the helical gear pump is the screw pump. Both gear and screw pumps are positive displacement... 

FIG. 10-55 Two- rotor screw pump. Courtesy ofWan en Quimhy Tump Co. )... 

FIG. 10-56 Single- rotor screw pump with an elastomeric lining. CouHesy of Moyno Tump Division, Rohhins [Pg.912]

McKelvey, J. M., U. Naire, and F. Haupt, Flow Gear Pumps and Screw Pumps Perform in Polymer-Processing Applications, Chem. Eng., V. 83, No. 20, 1976. 

Screw pumps are available in single or double-rotor (multiple) types. 

Figure 32.25 Effect of n on screw pump and centrifugal pump compared (after Sterling )...

An emulsified fatty acid soap (e.g., magnesium or iron tallate, having between 8 and 18% metal content. This type of product is cationic and may exhibit some partial solubility in both oil and water. It can be fed by pump (usually a progressive cavity pump or a screw pump). 

A most important class of pump for dealing with highly viscous material is represented by the screw extruder used in the polymer industry. Extruders find their main application in the manufacture of simple and complex sections (rods, tubes, headings, curtain rails, rainwater gutterings and a multitude of other shapes). However, the shape of section produced in a given material is dependent only on the profile of the hole through which the fluid is pushed just before it cools and solidifies. The screw pump is of more general application and will be considered first. 

Figure 8.16. Planar model of part of a screw pump...

Figure 8.18. Velocity profile produced between screw pump surfaces (u) with no restriction on fluid flow (/>) with no net flow (total restriction) (c) with a partially restricted discharge...

Screw pumps, viscous material 329 Seals, mechanical 339 Sears. F, W. 172.179... 

With the advent of high-pressure feeders after World War II (e.g., blow tanks, screw pumps), many designers and users began to apply pneumatic conveying to much greater distances and/or capacities (e.g.,... 

Multiple reactor processes, 20 170 Multiple screw pumps, 21 73 Multiple spinnerette per bank process,... 

Three-phase furnaces, 12 304 Three-roll mills, 18 65 Three-screw pumps, 21 73 Three-stage (ternary) cascade refrigeration systems, 21 549-550 Three-stage refrigeration systems,... 

Campbell, G. A. Wang, C., Cheng, H., Bullwinkel, M., and te-Riele, M. A., Investigation of Elow Rate and Viscous Dissipation in a Single Screw Pump-Extruder, Int. Polym. Process., 16, 323 (2001)... 

Campbell, G.A., Spalding, M.A., and Carlson, F., Prediction of Screw Temperature Rise in Single Screw-Pump Extruders, SPE ANTEC Tech. Papers, 54, 267 (2008)... 

Campbell, G.A., Sweeney, P.A., Dontula, N., and Wang, Ch., Frame Indifference Fluid Flow in Single Screw Pumps and Extruders, Int. Polym. Process., 11, 199 (1996)... 

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