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Heating and cooling: Evaporative cooling

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1 to 18 of 18

  1.  
    • CommentAuthortony
    • CommentTimeAug 25th 2022
     
    Opinions on evaporative cooling?
    •  
      CommentAuthorfostertom
    • CommentTimeAug 26th 2022
     
    No good in the humid tropics, where it wd be most valuable.

    The other day I learned that the traditional Scot, having to sleep outdoors, would slightly wet his woolen kilt. With those little water-absorbing sacs, could that be a case of condensative warming?
    • CommentAuthorMike1
    • CommentTimeAug 26th 2022 edited
     
    It has a few thousand years of history behind it, so great in principle, except when humidity is high. Though not all mechanisms used are compatible with the winter UK climate.
    For some ideas, see https://www.bbc.com/future/article/20190822-are-there-alternatives-to-air-conditioning

    There are a few thoughts on this forum too, for example here:
    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16687#Comment_282890
    • CommentAuthortony
    • CommentTimeAug 27th 2022
     
    • CommentAuthorMike1
    • CommentTimeAug 27th 2022 edited
     
    Posted By: tonyBlauberg Komfort Evaporative Cooler
    Thanks - that's the kind of thing I'd imagined in that thread (the link above) from 2 years ago! Interesting to see that someone is now making one for domestic use - maybe they read the discussion here?!
    A shame about the crazy price though...
    • CommentAuthorCliff Pope
    • CommentTimeAug 28th 2022
     
    Of course coolers for individual items have been used for centuries. We used to stand milk bottles in a shallow bowl and place a special porous pot over them. A cheaper alternative was a foam rubber jacket.
    •  
      CommentAuthordjh
    • CommentTimeAug 28th 2022
     
    Posted By: Cliff PopeWe used to stand milk bottles in a shallow bowl and place a special porous pot over them.
    The important bit was the water in the bowl. :bigsmile: Any terracotta or similar object that was big enough to cover the bottle would do.
  8.  
    Posted By: djhThe important bit was the water in the bowl.http:///newforum/extensions/Vanillacons/smilies/standard/bigsmile.gif" alt=":bigsmile:" title=":bigsmile:" >Any terracotta or similar object that was big enough to cover the bottle would do.

    Or even a towel over the bottle providing it is in the water to wick up the water to then evaporate.
  9.  
    Wet bulb temperature is typically ~5⁰C cooler than dry bulb, unless the air is particularly dry.

    That might or might not be enough cooling for your purposes - could take the edge off a hot room, but I'd like my milk kept a bit cooler than that!
    • CommentAuthorCliff Pope
    • CommentTimeAug 29th 2022
     
    I think that's why generations of children used to hate milk - lukewarm just starting to go off, blobs of goo separating out. Then came refrigerators, and a glass of chilled milk became the most refreshing drink in the world.
  11.  
    :-) I had a pocket money job many years ago, helping a milk delivery man. Some older customers still didn't have fridges and relied on having fresh milk delivered daily, to be kept in a pantry that had openings both to the outdoors and to the kitchen. Any milk that was unused by the end of the day, went down the sink. Progress can be a good thing!



    Looking at the evaporative MHRV cooling link, it suggests 6 degrees of cooling are available. Multiplied by the airflow of a MHRV system , that seems to amount to a couple of hundred Watts of cooling. That's not much considering the price, but as has been discussed before, ventilation systems are only able to move small amounts of heat. A duct-mounted heat pump would perhaps give more degrees of cooling (or heating when needed) and could be a good match for some PV.
  12.  
    Posted By: WillInAberdeenAny milk that was unused by the end of the day, went down the sink. Progress can be a good thing!

    A bit off topic - But when I was a lad milk came in quart bottles, daily and milk was never thrown away, if it went sour it was hung in a cloth on the kitchen tap for cottage cheese the next day. I have found that todays supermarket milk doesn't go sour but goes bad and become unusable.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 30th 2022
     
    Posted By: Peter_in_Hungarytodays supermarket milk doesn't go sour but goes bad and become unusable
    Like irradiated fruit - zombies which can't 'die' naturally but degrade anyway in some ghastly way.
    • CommentAuthorCliff Pope
    • CommentTimeAug 30th 2022
     
    <blockquote><cite>Posted By: Peter_in_Hungary</cite>I have found that todays supermarket milk doesn't go sour but goes bad and become unusable.</blockquote>

    It also goes off after about a month even if kept frozen.
    "Milk" is curiously variable as between different supermarkets. Tesco's freezes well, CK's separates into components.
    Some work well when made into yoghurt, some are a disaster.
    • CommentAuthorowlman
    • CommentTimeAug 30th 2022
     
    Zombie fruit and veg all on their hols. swimming in a netherworld lake of rancid milk.
    I love it Tom, that image will stay with me.:bigsmile:
    •  
      CommentAuthorfostertom
    • CommentTimeAug 30th 2022 edited
     
    I said, a bit ha-ha
    Posted By: fostertomThe other day I learned that the traditional Scot, having to sleep outdoors, would slightly wet his woolen kilt. With those little water-absorbing sacs, could that be a case of condensative warming?
    but it made me realise that hydroscopic ab(ad?)sorbtion of water vapour into liquid held inside the interstices (sacs?) of an organic material's structure (so it doesn't feel wet) must be accompanied by heat release, opposite of evaporative cooling. It warms the material up.

    Could go a little way to explain cob's buildings' 'insulation' which is somewhat inexplicably better than it 'should' be.

    I'm trying to imagine what makes vapour condense to liquid while passing thro the 'sac's' wall - perhaps osmosis achieves that?
    •  
      CommentAuthordjh
    • CommentTimeAug 30th 2022
     
    Posted By: fostertomThe other day I learned that the traditional Scot, having to sleep outdoors, would slightly wet his woolen kilt. With those little water-absorbing sacs, could that be a case of condensative warming?
    So that's what Scotsmen keep in their sporrans - a small misting bottle :bigsmile:
    • CommentAuthorleo_r
    • CommentTimeAug 31st 2022
     
    I found this video really interesting - the guy at Tech Ingredients built a multi-stage evaporative cooler with heat exchanger. https://www.youtube.com/watch?v=R_g4nT4a28U

    Having briefly experimented with an evaporative cooling fan (a regular fan which pumps water over an evaporative material while blowing air over it), it's clear it definitely doesn't make sense without a heat exchanger - the room became uncomfortably humid very quickly.

    In places with low humidity and relatively large amounts of water available, it's very compelling. It seems a bit too niche and specific to see wide adoption though.

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