Water flow rate and drip surface tension

  • #1

Summary:

flow rate, water, drips, drop, surface tension
hello
i have a drip tube with water dripping and when i increase the flow rate or frequency of drips they get bigger/more massive.
i see the equation mass x gravity = 3.14(tube diameter)(surface tension)
my mass is changing but not gravity, 3.14 or tube diameter so surface tension must be related to flow rate but I cant find anything online on how to figure this out.
conversely I have a known flow rate and mass and want to determine tube diameter but unsure how to get it as it appears surface tension must be related to flow rate but I dont know how
 

Answers and Replies

  • #2
jrmichler
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Try search term liquid drop formation. Are you collecting data on drop size vs flow rate and tube diameter? Does the liquid attach to the tube ID or OD?
 
  • #3
berkeman
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i have a drip tube with water dripping and when i increase the flow rate or frequency of drips they get bigger/more massive.
I have not seen that with IV administration. The drop size depends on the IV tubing size (macrodrip or microdrip), but not on the flow rate (in drops per minute). What size tubing are you using, and how are you controlling the flow?

https://www.mometrix.com/academy/calculations-of-drip-rates/

https://www.recoveringself.com/health/iv-drip-therapy-the-science-behind-the-fad

1603463967726.png
 
  • #4
drip weight absolutely depends on flow rate. I am using normal sized equipment
 
  • #5
jrmichler
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So show us some data on drop size vs flow rate. It's easy enough to get accurate measurements: Flow per time divided by drops per time = volume per drop. Also a photo of your setup would be helpful.
 
  • #6
i have a known drop mass, known flow rate and need to calculate the diameter of the tube that it comes out of
 
  • #7
berkeman
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i have a known drop mass, known flow rate and need to calculate the diameter of the tube that it comes out of
That doesn't seem like an accurate way to control a flow rate. Can you please just say exactly what your design requirements are?

And if you want to control/meter a flow, a peristaltic pump is a good option usually. We use them all the time in medical applications (like IV infusions)...

https://www.graylineinc.com/whitepapers/peristaltic-pump-tubing.html

1603495345358.png
 
  • #8
i have stated my design requirements.

drip size .05 gram
flow rate 150grams/hour
how big hole of drip tube?

the answer should take into account flow rate as is I increase the flow rate, with the diameter calculated above the drip size will go up..............
 
Last edited by a moderator:
  • #9
Tom.G
Science Advisor
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Sorry @fdnovice7629, the drip size is highly dependent on the viscosity and surface tension of the fluid you are dripping. Try getting a drop of alcohol thru your device, then try getting a drop of honey thru it.

The only way to get numbers for a fluid with unknown characteristics is to run a bunch of experiments. Even in hospitals, the Intravenous Drips are controlled by a constriction upstream of the drip chamber, effectively controlling the pressure to regulate the flow.

Cheers,
Tom
 
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  • #10
berkeman
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i have stated my design requirements.

drip size .05 gram
flow rate 150grams/hour
how big hole of drip tube?

the answer should take into account flow rate as is I increase the flow rate, with the diameter calculated above the drip size will go up..............
Did you look into peristaltic pumps at all? 150cc/hr is certainly do-able with high accuracy...
 
  • #11
I am not here looking to purchase an item. I am here to determine the drip tube diameter required for my specs. It will be connected to an IV bag and then some other means of regulation will control the flow.
 

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