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Registered Member #1822
Joined: Fri Nov 21 2008, 08:04PM
Location:
Posts: 300
One of the unpleasant things about being a scuba diver is getting into a cold wet wetsuit. You cant put them into a clothes dryer because they are very heavy and would melt. My idea is to place them into a vacuum chamber with a standard ball valve to regulate pressure and have a car air conditioner compresser draw the vacuum. Would this be practical?
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I'd suggest just blowing air through it.
If you do use a vacuum pump you'll need a purge valve (I think that's what it's called) to allow air into the system between the chamber and pump, to flush water out of the pump (I think).
Registered Member #1822
Joined: Fri Nov 21 2008, 08:04PM
Location:
Posts: 300
Blowing air through wont work. The neoprene is very think and the water would need to flow to the surface for the fan to work. If The pressure was lowered then that should cause the water to evaporate.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
It won't work very well The water needs heat to evaporate and a neoprene wetsuit in a vacuum chamber is a very good thermal insulator. You could try a vacuum desiccator which relies on having a drying agent in the chamber.
Registered Member #1451
Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661
Bored Chemist wrote ...
The water needs heat to evaporate and a neoprene wetsuit in a vacuum chamber is a very good thermal insulator.
The point of putting it into the vacuum chamber is to lower the boiling point of water to a temperature below room temperature.
I bet it would work great as long as you can find a chamber large enough to fit it in. The pump would be the weak point. The lower the pressure the faster the water will evaporate. The pump will need to have enough throughput that it can pump out all of the water vapor as it forms.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Yea the pump would be the weak point, but you can dramatically decrease the vacuum needed for the water to boil by adding *some* heat. I have no idea what kind of vacuum you could expect out of a car A/C pump, but a pump that can pull a vacuum around 700 torr, water will evaporate at 100 degrees F.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
This "The lower the pressure the faster the water will evaporate." simply isn't true.
What happens is that the water boils, in doing so it extracts energy from itself and the surroundings and it cools. After a while it freezes. Ice does evaporate, but rather slowly. As you pull more air and vapour out you drop the pressure. The ice sublimes and , in doing so , gets even colder.
If you watch this clip you can see the water initially evaporating very quickly, but the rate falls off as the temperature drops. Fundamentally, you have to supply heat to evaporate the water. It's called the latent heat of vapourisation. The colder you get it, the more heat you need to add. A neoprene suit in a vacuum chamber isn't easy to warm (you could try shining light onto it.)
Don't wetsuits contain closed gas bubbles for insulation? Might cause issues under vacuum. Flowing warm dry air sounds good to me, and any moisture that can't remove isn't going to be giving a cold feeling to the suit anyway.
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