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watson.fawkes
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Quote: Originally posted by uchiacon  | | If you have a larger aspirator it's going to suck more air than a smaller one correct? Down to the vapour pressure of water I'd presume?
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The rate of an ejector pump is proportional to the surface area of contact between the working fluid and the
gas being pumped. The pumping mechanism is momentum transfer between the working fluid and the gas, so it's the total contact area between these two
that matters. So yes, a larger pump will pump faster, where you measure size by this surface area, not by the bulk size of the pump.
The vapor pressure of the working fluid is a lower limit. Depending on operator parameters, it may not be achievable. | Quote: | | However, My pump is a 46L/min job with 30 PSI, and I'm quite certain the bought aspirator could not take that much pressure. And the pump might fail
too. Without a pressure tank, it is harder to get a higher pressure correct? |
I fail to see what a pressure
tank has to do with this system. And 30 psi is a rather low pressure for most materials.
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uchiacon
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Yeah, but the pipe diameters are 1", and 1/2ing that diameters is sure to increase pressure. I think I'll just buy a aspirator attachment, I can't be
screwed making one. Its too complex, and I don't have the money or the time to do so.
I'm mainly concerned about the 46L/min, 760ml/s... isnt that a lot?
[Edited on 04-07-09 by uchiacon]
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watson.fawkes
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No. I don't
know what fundamental misunderstanding you have about pressure in fluid dynamics, but you've got one. Do some reading. Start with the Wikipedia
article on fluid dynamics. | Quote: | | I'm mainly concerned about the 46L/min, 760ml/s... isnt that a lot? |
The pump you've got is way overspecified
for a small aspirator.
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uchiacon
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ffffffffff....
So unless I could have part of that water being pumped through another tube leading off, the pump is kinda useless to me. Am I correct here? Maybe if
I could divert part of the water flow before the aspirator fitting then I wouldn't have to worry about too many L/s.
I just read this guide here
designer-drugs.com/pte/12.162.180.114/dcd/chemistry/equipment/aspirator.html and ran with that, considering these is absolutely fucking nothing on
this subject on the internets...
In which case, should I just try and resell this pump? I got it for $100 with normal retail 270. Should I flog it and try to get something smaller
with a more powerful PSI? Any reccommendations?
Oh, and theres also this vacuum pump going on trademe for $28... goes down to 10torr. If I set up a vapour trap then it would be ultimate for nitric
distillation right? Its really cheap, but it might go up to about $50-60... worth it? And for the vapour trap, possible to use a low volatility
solvent to catch the HNO3 vapours?
[Edited on 04-07-09 by uchiacon]
[Edited on 04-07-09 by uchiacon]
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watson.fawkes
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| Quote: Originally posted by uchiacon | | Maybe if I could divert part of the water flow before the aspirator fitting then I wouldn't have to worry about too many L/s. |
At some point you're going to have to try something without knowing in advance whether it will work. Why don't you do that sooner
than later? Learning the emotional skill of taking risks is a far more useful skill to develop than any particular skill with vacuum systems.
Using diversion valves seems like a perfectly reasonable solution to experimenting with a too-big pump. Use two, one on the aspirator line and one on
the dump line. (Or find a three-way valve, which is a little harder.) You can run your dump line back into an input tank, even if you're not making a
completely closed system.
What I would heartily recommend is using pressure and vacuum gauges. Put a pressure gauge on your pump supply, if only to make sure that you're not
overpressurizing your pipe. Put a simple vacuum gauge on a test chamber, to see how well your aspirator pumps down. Gauges are cheaper than you might
think, even if you have to mail-order them.
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uchiacon
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Thing is, I'm two years too young to get a job and I dont have the money to spend on experimentation.
Theres that pump on trademe, I'll see if I can get that. 10 torr is better than an aspirator can do. The nitric would boil at 30-40 C at that vacuum
wouldnt it?
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watson.fawkes
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There
are two kinds of risk here, and you're addressing them piecemeal. One is the risk of destroying equipment; the other is the risk of your experiment
not working. You express worry about the first risk by stating you don't have money, but you're not asking questions about how to avoid frying your
pump. You're asking questions about how to ensure that your distillation works the first time, but you're not acknowledging your fears. Now I can
offer some assistance about equipment, but my willingness to do so is limited by what you're willing to do for yourself.
The great replacement for money is time. So spend some time. You've repeatedly asked about boiling point under reduced pressure, but to my sight you
haven't been looking for a vapor pressure table for the solutions of interest. You have questions about pumps, but I haven't seen you trying to
understand the differences between differences in pump designs, what they do when overloaded, what a pressure/flow curve is, etc.
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uchiacon
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I'm not asking for sympathy, I'm simply asking a few straight questions, easily answered in a sentence or so. You're making out that I cant be screwed
doing any research. No, thats complete bullshit. I didn't construct my own ball mill, interpret other schematics and research for weeks on chlorate
cells to be told that.
I'm stating my circumstances, I'm not asking to be constantly spoonfed. I have some questions here that I just need simple answers to to steer me in
the right direction. I realise that I should have done a bit more research regarding fluid dynamics and such, and thank-you for steering me in that
direction. I am fourteen, not forty. What were you doing when you were 14?
And no, time is fucking NOT a substitute for money. Thats bullshit. Time? Can time buy me the necessary bits for my aspirator? Yeah, maybe if I had a
job. Sure, in few cases time can be a substitute for money, but not in mine.
Am I asking "ok, find me some designs, I can't be screwed pouring over the couple of topics here and what little information on this topic that there
is on the internet"? No, I am not a k3wl, I just have almost not idea where to start on this apart from 'fumbling around in the dark', as it is.
I wouldn't be asking these questions if they had been asked before in another thread. Now please, stop treating me like a fucking k3wl (christ, at
this age I should be encouraged) and either point out where I should read or give me the brief answer to the question.
"..but I haven't seen you trying to understand the differences between differences in pump designs, what they do when overloaded, what a pressure/flow
curve is, etc."
Ok, so imagine you're fourteen and somebody tells you that.
I'm no pump engineer, and no doubt it would take quite a few manuals to learn those things. If I had some information you needed, I wouldn't act like
you're acting to me, so why don't you pay me the same courtesy?
[Edited on 04-07-09 by uchiacon]
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hosko
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Removed cross-post. Multiple posts won't help you getting better answers or getting answers in less time. Please continue the discussion over here:
http://www.sciencemadness.org/talk/viewthread.php?tid=15104
[Edited on 23-10-11 by woelen]
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Texium
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Thread Moved
19-11-2023 at 16:50 |
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