Screw Pump Sizing: Calculations for Inverted Pumps

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Discussion Overview

The discussion centers around the calculations needed for sizing an inverted screw pump, which is characterized by fins attached to the inside of a rotating pipe rather than a traditional screw mechanism. Participants are seeking formulas to determine the pump's diameter, fin height, spiral pattern, and operational speed while handling varying amounts of dry powder.

Discussion Character

  • Technical explanation
  • Exploratory
  • Homework-related

Main Points Raised

  • One participant requests calculations for sizing an inverted screw pump, specifying the need for formulas related to diameter, fin height, spiral pattern, and speed.
  • Another participant suggests using equations for a regular screw pump, indicating that the orientation of the screw and casing does not affect the calculations.
  • A participant expresses difficulty in finding online resources for screw pump equations and notes that their design eliminates the screw shaft.
  • One participant recommends exploring Polymer Processing literature, particularly in the context of extrusion, and mentions specific authors and topics related to the rheological behavior of granular materials.

Areas of Agreement / Disagreement

There is no consensus on the specific calculations or resources for sizing the inverted screw pump. Participants have differing views on the applicability of regular screw pump equations and the availability of relevant literature.

Contextual Notes

Participants mention the importance of understanding the rheological behavior of granular materials and kinetic friction in the design of screw pumps, but the discussion does not resolve these complexities or provide definitive resources.

hmvyoral
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Does anyone know where i can get the calculations for sizing an inverted screw pump. Inverted being that there is no screw but the fins art attached to the inside of a pipe and the pipe is rotating. I am moving any where from 150 to 400 lbs of dry powder per minute, depending on the amount of powder being produced. I don't have the exact length yet, hence why i just need the formulas. The idea is to find the diameter, fin height, spiral patern, and speed. If anyone knows where i can get the calculations i would apreciate the help.
 
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hmvyoral said:
Does anyone know where i can get the calculations for sizing an inverted screw pump. Inverted being that there is no screw but the fins art attached to the inside of a pipe and the pipe is rotating. I am moving any where from 150 to 400 lbs of dry powder per minute, depending on the amount of powder being produced. I don't have the exact length yet, hence why i just need the formulas. The idea is to find the diameter, fin height, spiral patern, and speed. If anyone knows where i can get the calculations i would apreciate the help.

Use the equations for a regular screw pump. It doesn't matter whether the screw is rotating and the casing is stationary or the casing is rotating and the screw is stationary.
 
Chestermiller said:
Use the equations for a regular screw pump. It doesn't matter whether the screw is rotating and the casing is stationary or the casing is rotating and the screw is stationary.

I would like to use the equations for a screw pump, but i am unable to find any online. I had figured that everything would be the same because all i did was eliminiate the screw shaft and put the fins on the wall of the casing. If you know where i can get some calculations i would apreiciated it.
 
Try looking in the Polymer Processing literature in the area of extrusion. They use screw pumps (extruders) to compact and melt granular and powdery solids as part of producing a polymer melt. Look under the names of Bernhardt, Tadmor, Tadmor and Klein, and Osswald. In order to design a screw pump for a granular material, you need to have some idea of the rheological behavior of the granular material on a scale somewhat larger than the particle size. I'm not sure how much work has been done in this area, since I haven't followed it. But consider looking under the subject of Deformational Behavior of Granular Materials. In a screw pump, kinetic friction on the granular bed is also important. I hope this is helpful.
 
Thank you, I will start looking into that. I will let you know if i find anything.
 

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