Re: "Cheap" vacuum
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I agree with?Christopher Erickson.
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However, I also frequently encounter people who really want to do something a particular way, even if there are better ways to do it. We might try to talk someone out of riding a bicycle across the country, pointing out that it is cheaper to fly, much faster, and that while exercise is good for the health in moderation, when done to excess it is harmful, especially on public
roads behind and among motorists. But maybe the whole point was to do it on a bicycle. I was one of the first to try to get him to his goal in more efficient ways. But since this is a list for people interested in vacuum, and he really wants to cool
his beer in a homemade vacuum assisted zeolite refrigerator, let's just pretend that he won't win some contest unless the task is done using a vacuum and zeolites, and see what we can do to help. Whatever tricks we devise to produce a cheap
vacuum just might be useful to someone else. So far we have suggested: 1. Steam condensed by ice until the required vapor pressure is reached. 2. Liquid dense metals flowing down a meter or two of pipe.
3. Evacuating several bottles and connecting them one at a time to the chamber. 4. Using a port from a running internal combustion engine. 5. Buying a $130 roughing pump and a $30 inverter for a car.
I think we've talked him out of trying to pump that much volume by hand with a small hand pump. Some things we haven't (yet) discussed: A. Building a big syringe and using a car jack to pull a vacuum with it.
B. Filling a tank with oxygen and steel wool and igniting the wool electrically. C. Filling the tank with ammonia gas and opening a valve to a water bottle. D. Finding some low vapor pressure compound that is a liquid at room temp
? ? ?but a gas at some reasonable temperature (i.e. the steam idea, but with ? ? ?something that doesn't need to be chilled). E. Buying some used car batteries and connecting the pump and inverter to those
? ? ?so the car can be farther away from the cabin, and only used occasionally to ? ? ?recharge the batteries. F: Building a 33 foot high tower out of something cheap and use water and gravity
? ? ?to draw the vacuum (has the same vapor pressure problem -- needs cooling). G: Maybe that dense mud they use for drilling wells (barium sulfate or hematite) ? ? ?could be used so instead of a tower, you can just put it on the roof of the cabin.
? ? ?With mercury you could just use 800 millimeters, but a slurry of barium sulfate ? ? ?is 2.5 times heavier than water, so the roof only has to be 13 feet high. Using ? ? ?ethylene glycol instead of water would get the vapor pressure down to a quarter
? ? ?of what water has. ?So fill a tank with ethylene glycol and barium sulfate mud on ? ? ?the roof, and run a pipe down to a tank on the ground, and open a valve. Both ? ? ?barium sulfate and ethylene glycol are cheap. Glycerin will get you even lower vapor
? ? ?pressure, and olive oil even lower still. Safflower oil may be the best. It won't ? ? ?take a lot of oil -- the mud will mostly be barium sulfate or hematite. Hematite ? ? ?(rust powder) is the heavier of the two.
There are a lot of really bright people on this list -- we should be able to come up with a bunch of fun cheap ways to pull a vacuum. ----- Get a free science project every week! ""2011/6/18 Christopher Erickson <christopher.k.erickson@...>
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Simon Quellen Field