Designing a Twin Screw Pump - Why the Pressure Loss?

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Discussion Overview

The discussion revolves around the design considerations for a twin screw pump, specifically addressing the rationale behind having an outlet positioned at a higher level than the inlet. Participants explore the implications of this design choice on pressure dynamics and practical installation challenges.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion regarding the design of twin screw pumps, questioning why outlets are often higher than inlets, suggesting this may lead to pressure loss.
  • Another participant references Archimedes' screw as an example of a device designed to lift water, implying that height can be a functional aspect rather than a loss.
  • A different viewpoint states that pressure due to height is not a loss but rather a desired outcome of pump design, emphasizing the role of static pressure.
  • One participant suggests considering screw compressors in addition to pumps, hinting at broader applications and design principles.
  • A later reply discusses practical considerations for pump installation, noting that higher outlet positioning may facilitate access and serviceability in constrained spaces.

Areas of Agreement / Disagreement

Participants express differing views on whether the height difference between inlet and outlet constitutes a pressure loss or serves a functional purpose. The discussion remains unresolved with multiple perspectives presented.

Contextual Notes

Participants do not fully explore the mathematical implications of pressure changes related to height, nor do they clarify assumptions about fluid dynamics in the context of screw pump design.

steve2510
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I'm having to design a screw pump and I'm a bit confused about things, I've never really seen a screw pump before. I've decided upon a twin screw - screw pump and my first question is why do most examples have an outlet at a higher level than the input, surely that just leads to a pressure loss?

Example http://pimg.tradeindia.com/00110473/b/0/Twin-Screw-Pumps.jpg
 
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Pressure due to height isn't loss, it is the very thing pumps are designed to create (or its twin, static pressure).
 
steve2510 said:
I'm having to design a screw pump and I'm a bit confused about things, I've never really seen a screw pump before. I've decided upon a twin screw - screw pump and my first question is why do most examples have an outlet at a higher level than the input, surely that just leads to a pressure loss?

Example http://pimg.tradeindia.com/00110473/b/0/Twin-Screw-Pumps.jpg

From a purely pragmatic standpoint, remember that in use a compressor, like all equipment, is going to be installed in a room to support some other process. These things can be big, and every square foot of floor space costs money to build, or you might be trying to fit the thing into the same footprint as a compressor being replaced. Also, imagine being in a room with a large cabinet with pipes entering and exiting horizontally. Sort of hard to walk around it, right? That means it's difficult to service, and you can't even move the thing into place without having to move pipework. While the inlet might very well be connected to a large filter element nearby, the outlet pipes are probably going to be overhead simply for reasons of access. So if you have to come out of the compressor and make a 90 degree turn upwards immediately, why not just point the outlet in that direction to begin with?
 
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