JohnBee
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Trying to understand vacuum specs...
I'd like to lower the boiling point of water to room temp but discovered that my pump which can pull 88 Kpa. does not have the chops to pull it off. I
could have sworn I saw 96 on the indicator at one point, but it looks like diaphragm pumps have their limits.
And so I've been looking at other pumps, but it seems that every manufacturer is intent on using different measurement for max vacuum ratings which
has proven to be quite confusing to say the least. ie.
Kpa: 0-90
.095 Mpa
2 BARG
25.5 in. Hg
1 x 10^4 TOR
That said, If anyone can recommend a pump /type or model that they know from experience has the capacity to get the job done, that would be great
also. Though this entire max vacuum pressure rating scheme, seems like a rather daunting task to work through :/
[Edited on 14-6-2015 by JohnBee]
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Sulaiman
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here is a table of b.p. for water vs. pressure http://www.jbind.com/pdf/Cross-Reference-of-Boiling-Temps.pd...
29.42 inches (of mercury) vacuum required for water to boil at 15 C
12,700 microns = 12.7 mm Hg absolute pressure
12.7 mm Hg = 101.325 x (12.7/760) = 1.693 kpa
or 1.693 - 101.325 = -99.63 kpa relative to atmospheric pressure.
your 88 kpa diaphragm pump would (in theory) give an absolute vacuum pressure of 101.325 - 88 = 13.325 kpa
(760 mm Hg =760 torr = 101.325 kpa = 'standard' atmospheric pressure, often 100 kpa is used)
in mm Hg that is (13.325/101.325) x 760 = 100 mm Hg approx.
which, according to the table would require just over 50C to boil water.
I tried two cheap -80 kpa eBay vacuum pumps in series ... the low pressure side stalled the motor.
[Edited on 14-6-2015 by Sulaiman]
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unionised
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Also remember that many pumps are not designed to pump just water vapour like that.
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JohnBee
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Excellent info. guys!
Would a condensation trap solve the issue of vapour for the pump?
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JohnBee
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So I think I've found some pretty decent pumps on eBay but I just can't seem to make sense of the specs.
For example are the following ratings sufficient to boil water at room temp?
29.9" Hg
3.8 X 10-4 Torr
1 x 10-4 Torr
Another states: 15 Microns of total pressure AND 2x10-1Pa or partial pressure (?)
And finally, 10mBar
:/
[Edited on 15-6-2015 by JohnBee]
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Sulaiman
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Quote: Originally posted by JohnBee  | .
29.9" Hg
3.8 X 10-4 Torr
1 x 10-4 Torr
Another states: 15 Microns of total pressure AND 2x10-1Pa or partial pressure (?)
And finally, 10mBar
[Edited on 15-6-2015 by JohnBee] |
all of the above will boil water below (normal) room temperature
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