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Thread: vacuum drying ?

  1. #1 vacuum drying ? 
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    Not sure if this is chemistry or physics ..

    I've read about large industrial dryers, which don't use heat to dry what's inside, but which use vacuum pumps. The pump sucks all the air out, and the water inside boils away.

    HOWEVER

    I tried to reproduce this by placing a glass of water inside of a vacuum pump, and tuned it on. After 10 minutes, I checked, and the level of water didn't even move a mm.

    Do you know why that didn't happen ? Theoreically, water starts evaporating quickly when placed in a vacuum chamber, right

    Thank you


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  3. #2  
    Forum Freshman Captain_Anubis's Avatar
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    I would imagine that the pump simply wasn't strong enough and too much air stayed in the container. I've seen water boil at room temperature, it's very cool and I know it should be working for you...


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  4. #3  
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    Great, thanks for the infos.

    So when the water boils, does it mean that it actually loses water ? Because when my teacher did it in class, I didn't see any steam on the water's surface.

    Also, what type of pump can get water to boil, in you opinion ? For ex would 29.9" Hg (0.50 mm Hg) be enough ?
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  5. #4  
    Moderator Moderator AlexP's Avatar
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    Is the reason the water boils at room temperature when placed in a vacuum because you're lowering the pressure to nothing?
    "There is a kind of lazy pleasure in useless and out-of-the-way erudition." -Jorge Luis Borges
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  6. #5  
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    Chemboy,

    The lower the air pressure, the lower the boiling temperature.
    It takes more energy to bring water to boil at sea level than in the mountains.

    The thing is, I'm not sure if it actually evaporates the water the same way as when it is heat boiled.
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