How to get from pump flow rate to pressure change

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Discussion Overview

The discussion revolves around determining the appropriate pump specifications needed to achieve a flow rate of 40 gallons per hour to a height of 8 feet, using the Bernoulli equation for initial calculations. Participants explore the relationship between flow rate, head, and pump capabilities while considering pressure changes and potential losses in the system.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • One participant calculates a required pressure change of 3.44 psi based on the Bernoulli equation but notes that available pumps have a maximum head lower than 8 feet.
  • Another participant asserts that increasing flow rate will not compensate for a pump's inability to deliver the necessary head, suggesting the need for a pump that can achieve at least 8 feet of head or a redesign of the piping system.
  • A participant expresses curiosity about the principles of fluid mechanics and the relationship between flow rate and head.
  • A link is provided to a product comparison that includes head values for various pumps.
  • A question is raised regarding the fundamental reasons why a pump capable of delivering 200 gph to a height of 5 feet cannot also deliver 100 gph to a height of 10 feet.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to selecting a pump, with differing views on the relationship between flow rate and head capabilities remaining unresolved.

Contextual Notes

Participants have not fully explored the implications of pressure losses in the piping system, which may affect the overall requirements for pump selection.

zzinfinity
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Hi,
Essentially what I need is a pump that will pump 40 gallons of water per hour to a height of 8 feet. Ignoring pressure losses in the lines (for now) I used the bernouli equation to determine that I need a pressure change of 3.44 psi in my pump. I found these pumps that look suitable but all list a max head far lower than the 8 feet I need. http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=21414

I was thinking maybe just use one with a higher volume flow to compensate for the head loss. Maybe the 100 gph one? Is there a way to determine exactly what I need? Thanks!
 
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If the pump cannot deliver a head greater than 8', increasing the flow will not compensate. Find a pump which can deliver at least 8' of head, or re-design the piping system to reduce the head loss.
 
Fascinating. Fluid mechanics has always baffled me. Thanks!
 
Out of curiosity, is there a fundamental reason why a pump that can pump 200 gph to a height of 5 feet, can't also pump 100 gph to a height of 10 feet?
 

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