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Thread: water destilation

  1. #1 water destilation 
    Forum Freshman
    Join Date
    Nov 2009
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    Hi everyone

    I am currently designing a system to purify water as part of my engineering course.
    My team had the idea to distil the water. This could easily be done as the place where it would be used receives a lot of sunlight (outback Australia). However I started think for ways to improve our system and I quickly realized the lowering the pressure would lower the boiling point.
    Now If that pressure is low enough to get the boiling point below the dew point of the outside air. Then we could insulate the box and try to condense water with the box because its temperature would not rise above the boiling point.
    The biggest problem is: Does the condenser need to have a lower temperature than the boiler side? Or would it be enough to blow hot air (which we get from the outside) over the boiler side?
    It the latter would work then we would have a great way to collect at least some extra water

    Many thank in advance


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  3. #2  
    Forum Isotope Bunbury's Avatar
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    Sep 2007
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    Yes, the air you use for condensing the steam has to be at a lower temperature than the steam. You are removing the latent heat and the second law of thermodynamics tells you heat will only travel from a warmer to a colder body unless mechanical means are applied.

    You use the condenser to pull a vacuum and get the boiling point lower, but above ambient temperature. Vacuum systems tend to draw air in through leaks and you will then need an air ejector to remove infiltrated air.


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  4. #3  
    Forum Ph.D.
    Join Date
    Jan 2009
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    Dew pt is the temp at const pressure that humid air will condese out water,ie dew.
    thus your vacuum scheme will not work. you need to cool the air. or you can go to home depot and buy a dehumidifier
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