| Topic: |
Science > Physics |
| User: |
"" |
| Date: |
26 Sep 2006 10:53:34 PM |
| Object: |
Increase surface tension of water |
I building a project that requires a liquid to be dripped at the
fastest possible rate. Right now I'm using water coming out of a
little tube, this works pretty well but I'd like to get the most drops
possible per second. When I increase the flow rate, the water will
collapse into a stream.
I imagine that if I were doing the same with mercury, I'd have much
better success since it has a much higher surface tension. (Is my
hypothesis correct?)
So, which readily available (cheap, nontoxic) liquids can I use, or
what can I add to water, to obtain a liquid with a higher surface
tension?
Finally, if I'm stuck with plain old water, is distilled water going to
be have a significantly better surface tension than tap water?
Thanks for your input..
-sam
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| User: "Joachim Pimiskern" |
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| Title: Re: Increase surface tension of water |
09 Oct 2006 09:43:18 AM |
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<randomname12345@gmail.com> schrieb:
I building a project that requires a liquid to be dripped at the
fastest possible rate. Right now I'm using water coming out of a
little tube, this works pretty well but I'd like to get the most drops
possible per second. When I increase the flow rate, the water will
collapse into a stream.
Maybe you should make the tube opening triangular.
Some articles on droplet physics:
http://www.newscientist.com/article.ns?id=dn4397
http://physicsweb.org/articles/news/7/11/8
http://www.physorg.com/news9547.html
http://focus.aps.org/story/v11/st14
http://www.aip.org/pnu/2005/split/745-2.html
http://www.physorg.com/news75478692.html
http://www.physorg.com/news6312.html
http://www.physorg.com/news8718.html
http://physicsweb.org/articles/news/8/9/3/1
http://physicsweb.org/articles/news/9/7/14/1
http://physicsweb.org/articles/news/10/4/4/1
http://physicsweb.org/articles/news/9/3/14/1
Regards,
Joachim
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| User: "CWatters" |
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| Title: Re: Increase surface tension of water |
09 Oct 2006 01:59:14 PM |
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I building a project that requires a liquid to be dripped at the
fastest possible rate. Right now I'm using water coming out of a
little tube, this works pretty well but I'd like to get the most drops
possible per second. When I increase the flow rate, the water will
collapse into a stream.
How about using something like a gear pump with every other "tooth" missing.
eg to ensure the drops leave fast and with gaps.
or how about using an inkjet printer head?
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| User: "tadchem" |
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| Title: Re: Increase surface tension of water |
09 Oct 2006 02:39:55 PM |
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Joachim Pimiskern wrote:
<randomname12345@gmail.com> schrieb:
I building a project that requires a liquid to be dripped at the
fastest possible rate. Right now I'm using water coming out of a
little tube, this works pretty well but I'd like to get the most drops
possible per second. When I increase the flow rate, the water will
collapse into a stream.
Maybe you should make the tube opening triangular.
Some articles on droplet physics:
http://www.newscientist.com/article.ns?id=dn4397
http://physicsweb.org/articles/news/7/11/8
http://www.physorg.com/news9547.html
http://focus.aps.org/story/v11/st14
http://www.aip.org/pnu/2005/split/745-2.html
http://www.physorg.com/news75478692.html
http://www.physorg.com/news6312.html
http://www.physorg.com/news8718.html
http://physicsweb.org/articles/news/8/9/3/1
http://physicsweb.org/articles/news/9/7/14/1
http://physicsweb.org/articles/news/10/4/4/1
http://physicsweb.org/articles/news/9/3/14/1
Nice idea. I had not heard of this one before, but you have done your
homework well.
Another phenomenon I have noticed is that when the liquid *fails* to
'wet' (adhere through surface tension) to the material of the orifice
(as aqueous solutions adhere to the tip of a buret), the drops are
significantly smaller. For this reason I used to coat the tip of my
buret lightly with silicone grease (keeping the orifice itself clear)
to insure smaller drops for those titrations with very sharp end
points.
I can't answer to the relative repeatibility of the smaller drops or to
the flow rate, but the smaller drops made for a finer resolution in the
measurements.
I can also add that, at least in the viscous flow regime, the flow rate
varies quadratically with the pressure drop through the orifice (within
reason, of course). Elementary fluid mechanics texts (often found in
the hands of chemical engineers) can provide more explicit equations.
Tom Davidson
Richmond, VA
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| User: "Sam Wormley" |
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| Title: Re: Increase surface tension of water |
26 Sep 2006 11:04:12 PM |
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wrote:
I building a project that requires a liquid to be dripped at the
fastest possible rate. Right now I'm using water coming out of a
little tube, this works pretty well but I'd like to get the most drops
possible per second. When I increase the flow rate, the water will
collapse into a stream.
I imagine that if I were doing the same with mercury, I'd have much
better success since it has a much higher surface tension. (Is my
hypothesis correct?)
So, which readily available (cheap, nontoxic) liquids can I use, or
what can I add to water, to obtain a liquid with a higher surface
tension?
Finally, if I'm stuck with plain old water, is distilled water going to
be have a significantly better surface tension than tap water?
Thanks for your input..
-sam
A simple experiment is worth a thousand expert opinions!
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| User: "Andy Resnick" |
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| Title: Re: Increase surface tension of water |
27 Sep 2006 08:05:09 AM |
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wrote:
I building a project that requires a liquid to be dripped at the
fastest possible rate. Right now I'm using water coming out of a
little tube, this works pretty well but I'd like to get the most drops
possible per second. When I increase the flow rate, the water will
collapse into a stream.
I imagine that if I were doing the same with mercury, I'd have much
better success since it has a much higher surface tension. (Is my
hypothesis correct?)
So, which readily available (cheap, nontoxic) liquids can I use, or
what can I add to water, to obtain a liquid with a higher surface
tension?
Finally, if I'm stuck with plain old water, is distilled water going to
be have a significantly better surface tension than tap water?
Pure water has a very high interfacial energy to begin with (72 dyn/cm),
and adding small amounts of stuff to water will significantly decrease
the interfacial energy- so double distilled water is better than tap.
The pinching of a jet to a series of drops is controlled by both the
interfacial energy and the viscosity: drop size is given by interfacial
energy (it controls the wavelength of deformation), and rate of collapse
is given by viscosity.
Do you have freedom to choose the drop size? Forcing fluid through a
small orifice will result in a train of small drops, and the drop rate
will increase accordingly- think inkjet technology.
If you can vibrate the tube (with a loudspeaker, for example), the jet
will break up faster, also. But the the drops may splatter all over the
place.
--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University
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| User: "" |
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| Title: Re: Increase surface tension of water |
27 Sep 2006 12:49:25 AM |
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I've noticed that when water is mixed with a very tiny amount of dish
soap (not sure of the ratio but barely enough to even make bubble),
droplets of this water tend to bead on the surface of the water and
even slide around for a while before disappearing. I imagine that this
is indicative of an increased surface tention.
Hope it helps. :)
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