Pressure drop in a water manifold

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Discussion Overview

The discussion revolves around the pressure drop in a water manifold system designed to split a single flow line into multiple smaller lines for a cooling application. Participants explore the implications of this design on achieving uniform flow rates across the smaller lines, considering factors such as line length, diameter, and potential need for flow regulation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • David Schlaud presents a scenario involving a water chiller with a specified flow rate and pressure, expressing concern about nonuniform flow rates when splitting the main line into eight smaller lines.
  • Some participants acknowledge the possibility of nonuniform flow and inquire about the specific assistance needed.
  • David seeks mathematical validation for achieving uniform flow, questioning whether it is feasible without individual valves for each line.
  • One participant suggests that if the lengths of the smaller lines are significantly longer than the manifold and are identical in characteristics, uniform flow may be achievable, provided the manifold's flow area is sufficiently larger than that of the individual lines.
  • Concerns are raised about variations in line characteristics (length, elevation, bends) potentially leading to different flow rates, emphasizing the need for equal total restrictions in each line.
  • A suggestion is made to refer to a paper on pipe flow analysis for further understanding, although it is noted that this may not be worthwhile unless there is a strong interest in the topic.

Areas of Agreement / Disagreement

Participants generally agree that achieving uniform flow is complex and contingent on several factors, but there is no consensus on whether uniform flow can be guaranteed without additional measures such as valves.

Contextual Notes

Assumptions regarding line characteristics, flow area ratios, and the influence of bends and elevation differences are noted but not resolved. The discussion highlights the challenges in performing flow analysis without a strong background in fluid dynamics.

dschlaud
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Hi all,

This is what I currently have.
Water chiller with a flowrate of 2GPM (Choked to 2GPM)
Ti= 50F
H20
Pi=55-60psi

It is a closed loop system. I am looking to split 1 line at 2 GPM (55-60psi) into 8 smaller lines that will run into my cooling jacket. All 8 lines are same length and size. The manifold I am thinking of using is this one, (http://www.mcmaster.com/#5469k171/=8j52d0). My main concern is that the pressure drop along the manifold is going to create nonuniform flow rates between the 8 lines.

Manifold Inlet line is 3/8" ID and the manifold outlet lines are .17" ID.

Thanks in advance,

David Schlaud
 
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Yes, that's a real possibility. What are you looking for?
 
Q_Goest said:
Yes, that's a real possibility. What are you looking for?

I am hoping to get some help or direction so that I can say mathematically that I have uniform flow. Or is it not even possible to have uniform flow in a manifold like the one I have noted without putting a valve in each line. Fluids is not my strong point.

I plan on verifying experimentally but I would like to do calculations first to back up my theory/game plan.
 
If the length of your 8 lines is large compared to the length of the manifold (say more than 10 times) and assuming the 8 lines are identical in length and number of bends, and assuming the flow area of the manifold is at least 8 times larger than one of the tubes, then the flow through each of the tubes will be roughly the same.

If the lines are different lengths, different elevations or number of bends, or if there is anything different about them at all, then they might have different flow through each. Basically, you want to add up the total restriction for each line and make sure they are equal.

It's not easy to do the flow analysis without having some background in it. If you really want to try, you could go through the paper found on this link:
https://www.physicsforums.com/showthread.php?t=179830&

... but honestly, I wouldn't waste my time if unless you're really interested in learning how to do pipe flow analysis.
 

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