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Hi Knowledgeable folks,

Since boiling point of a liquid can be reduced via pressure reduction. I was wondering whether this is possible: Add some liquid (alcohol or Water) in a container, reduce the pressure inside the container so that, say the liquid inside can boil at say 10 degree Celsius (50 degree Fahrenheit) and seal the container air-tight. Now if I insulate the container well and at the top of the container place a cooling device (peltier, ice, chill water - which can produce say 5 degree Celsius/41 degree Fahrenheit cooling). Will/Can the water/alcohol inside the container freeze?. I was thinking since the container has low pressure and if he vapor inside can be condensed repeatedly using cooling - which will vacuum and the liquid inside can boil and get frozen - is it possible (would be a easy refrigerator) - since now one has done this perhaps there is something that I must be missing and wanted to know what that is.

Thanks a lot for your time and sharing.

Take care.

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Exactly the experiment you describe is shown in this video around 8 minutes in.

This is called evaporative cooling and indeed has been used for cooling things for all of recorded history. indeed, assuming you possess sweat glands your own body uses evaporative cooling. Actually your refrigerator uses evaporative cooling as well, but it keeps the evaporating liquid inside a sealed system.

Reducing the pressure increases the effectiveness of the evaporative cooling, but you have to use energy to pump out the air so you don't get the extra cooling for free.

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  • $\begingroup$ Thanks a lot John. In the above youtube experiment Boiling happens via external heatsource/higher boiling point OR via continuous vacuum via a vacuum pump. I wanted to know if can be done mid-way, that is the water is kept inside bell jar - vacuum created via a pup and valve closed (no more vacuum pulling via a pump). At this point, can I apply some external cooling (like the prof. did with his hands in the video, cool the vapor inside and boil the liquid in its own heat and freeze it?. In other words apply low energy cooling externally and get freezing. Thanks again. $\endgroup$
    – Ramanathan
    Commented Feb 9, 2016 at 7:09
  • $\begingroup$ In other words, the work of the vacuum pump is done by our external cooler - which keeps on cooling the vapor inside to convert it to liquid, which creates vacuum - which means the liquid boils with its own heat and becomes frozen. Thanks. $\endgroup$
    – Ramanathan
    Commented Feb 9, 2016 at 7:16
  • $\begingroup$ Reducing the pressure increases the effectiveness of evaporative cooling, but it becomes more difficult to condense the vapors at the top of your device (aka, a heat pipe) because the condensation temperature is lowered by the lower pressure. $\endgroup$
    – David White
    Commented Dec 4, 2016 at 19:01

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