Syrup or milk flowing down a tube

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Discussion Overview

The discussion revolves around the challenges of getting thick liquids, specifically syrup, to flow through a tube connected to a bottle. Participants explore various factors affecting flow, including viscosity, tube diameter, and air venting, while considering practical modifications to improve the setup.

Discussion Character

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

Main Points Raised

  • One participant notes that the viscosity of syrup is much higher than that of water or wine, which could be causing the slow flow.
  • Another suggests that heating the syrup could reduce viscosity, but acknowledges that heating is not an option for the original poster.
  • Some participants propose using larger diameter tubing to facilitate flow, with suggestions of doubling or even significantly increasing the diameter.
  • There is a discussion about the effectiveness of air vents, with some arguing that smaller diameter air vents may allow for better air flow compared to larger ones.
  • One participant mentions the importance of the air tube's position, suggesting it should be above the syrup level to allow air to enter effectively.
  • Another participant recommends decanting the syrup into a bottle with a wider neck to improve flow speed.
  • There is a suggestion to connect the air tube to the spout from the outside rather than the inside to reduce obstruction.
  • Participants discuss the concept of cross-sectional area (CSA) and its relevance to flow, with one seeking clarification on the term.

Areas of Agreement / Disagreement

Participants express a variety of approaches and modifications to improve syrup flow, but there is no consensus on a single solution. Multiple competing views on the effectiveness of different methods remain present throughout the discussion.

Contextual Notes

Limitations include the unresolved nature of the effects of viscosity on flow, the dependence on tube diameter and air vent size, and the specific constraints of not being able to heat the syrup or change the bottle.

oemmake
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Hello everyone,

I really feel out of my depth here, especially with this simple question. I'm trying to rig something up and understand why it's not working. With a pipe connected to a wine bottle sized bottle, syrup won't flow into the pipe (1cm diameter, 60cm long, down to a tap). For normal liquids like wine or water, this system seems to work ok:

33v0kmp.jpg


However, with thicker liquids (i.e. sugar syrup, (consistency similar to full fat milk, its not flowing). I'm hoping for pointers on how to make the syrup flow down the pipe once the tap at the bottom is opened at the bottom. Right now it's not flowing at all. I've been tinkering with pipes and connections, such as the image below:

2r6grwp.jpg


What would I need to do to the first drawing, to make thicker liquids flow easier?

many thanks / simon
 
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The viscosity of the problem fluids are much higher than that of milk and wine. So they are going to flow very slowly. DONT PRESSURIZE THE AIR. THIS IS VERY DANGEROUS. Maybe you could heat the more viscous fluids so that their viscosity is lower. Otherwise, use much larger diameter tubing (maybe twice as large or even more).

Chet
 
Understand the range of viscousities. Am only concerned with milk + syrups for now and how to increase flow. Heat is not an option, but larger diameter is. Am trying that now. Still open to other ideas (i.e. larger air vent? higher air vent position) - smaller diameter air vents seem to work better than larger diameter ones and I have no clue as to why.
 
I think, a bit like in Jaws, you're going to need a fatter tube. (Wider topped bottle etc.)
The air bleed tube can, of course, be very small diameter to help you there. The air flows so easily that even a finite gap will let enough in. When pouring water or fuel from a large inverted can with a long spout, you only need to loosen the connection a tiny amount for the liquid to gush out and for plenty enough air to gush in and for the 'glooping' to stop.
Is the top of your air tube above the internal surface of the syrup? That could be important.
 
sophiecentaur said:
I think, a bit like in Jaws, you're going to need a fatter tube. (Wider topped bottle etc.)
The air bleed tube can, of course, be very small diameter to help you there. The air flows so easily that even a finite gap will let enough in. When pouring water or fuel from a large inverted can with a long spout, you only need to loosen the connection a tiny amount for the liquid to gush out and for plenty enough air to gush in and for the 'glooping' to stop.
Is the top of your air tube above the internal surface of the syrup? That could be important.

Thank you. I thought bigger air bleed, more air flow. I was wrong. I will keep it small. The top of the air tube is inline with the spout, such that, the bottom of the bottle is raised higher than the air tube top. Perhaps I need to raise the top of the air tube so that it is much higher than the bottom end raised bottle...
 
The air tube can be very long so no syrup can run out of it. Take it right to the 'bottom' of the bottle, above the syrup level.
The ideal solution, though, would be to decant (at your leisure) into a dispensing bottle with a much bigger neck diameter. A wine bottle(?) has a very narrow neck for that sort of job. The speed of flow will tend to be better than pro rata with the cross sectional area of the tubing.
Could the syrup not be warmed up whilst decanting? That could speed things up a bit.
 
sophiecentaur said:
The air tube can be very long so no syrup can run out of it. Take it right to the 'bottom' of the bottle, above the syrup level.
The ideal solution, though, would be to decant (at your leisure) into a dispensing bottle with a much bigger neck diameter. A wine bottle(?) has a very narrow neck for that sort of job. The speed of flow will tend to be better than pro rata with the cross sectional area of the tubing.
Could the syrup not be warmed up whilst decanting? That could speed things up a bit.

thank you again.

heat isn't an option, nor is changing the bottle - unfortunately. I do have a little flow, just need to make improvements to the setup to increase it.

Air tube to right the bottom of the bottle is a good starting point for tweaking this. I will try making a much larger green part (see 1st image), that should help a bit.

I will also search for the smallest diameter air bleed tube to reduce obstruction in the spout.

I will also try connected to the spout via the outside, rather than inside
 
oemmake said:
thank you again.

heat isn't an option, nor is changing the bottle - unfortunately. I do have a little flow, just need to make improvements to the setup to increase it.

Air tube to right the bottom of the bottle is a good starting point for tweaking this. I will try making a much larger green part (see 1st image), that should help a bit.

I will also search for the smallest diameter air bleed tube to reduce obstruction in the spout.

I will also try connected to the spout via the outside, rather than inside

Good idea, that will give you a significant amount of 'free CSA'. As everything will be happening so slowly, I don't think you need to be to fussy about smooth transitions.
I bet eBay will have some very narrow plastic tubing available.

PS Is this brewing or "Breaking Bad" haha
 
  • #10
sophiecentaur said:
Good idea, that will give you a significant amount of 'free CSA'.

Thank you again. What is CSA?

sophiecentaur said:
PS Is this brewing or "Breaking Bad" haha

Secret... ;-) but you are more than welcome to join
 
  • #11
oemmake said:
Thank you again. What is CSA?



Secret... ;-) but you are more than welcome to join


Haha, CSA is cross sectional area.
If it involves eating or drinking I may join!
 
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  • #12
sophiecentaur said:
Haha, CSA is cross sectional area.
If it involves eating or drinking I may join!

Thank you again.

Deep beneath the surface of admirable intellect, we are all simple creatures when food or drink is involved ;-)
 
  • #13
Not far beneath! :approve:
 

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