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shadiya
Joined: 02 Feb 2008 Posts: 1285
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Posted: Sun Jun 02, 13 10:59 pm Post subject: Freezing water |
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I didn't do physics at school so can somebody clever please help? I've been wondering for a while about how one might go about filling an ice house, given that these days our winters are mostly mild. Then was reading one of my old farming books (honestly, they really are better than getting a life ) in which it described making giant ice cube trays for the very same purpose. However, as I have no idea how much coldness one needs to freeze how much water, I can't work out whether this is practical or not.
The trays described were about 12 by 24 by 12, inches. Living in Oxford, well, near enough, we don't normally get more than a couple of weeks of snow and as I keep meaning to but have never actually got round to keeping weather records, I've no idea how many days and nights below freezing we get. So what I'd like help with is how long it'd take to freeze that depth of water at say -1, so I can try and guesstimate whether this is one of my more loony ideas or not.
Thank you clever people! |
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Mistress Rose
Joined: 21 Jul 2011 Posts: 15600
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Posted: Mon Jun 03, 13 7:36 am Post subject: |
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Unless you have a number of cold days and nights, I wouldn't bother. The old ice houses used to take a lot of filling, had to have a drain in the bottom, and ran out after a while. I would stick to a fridge.
You seem to be colder than we are, but I think we would be lucky to freeze or fill one of your trays virtually any year.
If you are thinking of freezing, you need to calculate the energy needed to reduce the temperature of the water you put in the trays to at least 0 deg C. This will be the volume (mass) of the water x the number of degrees of temperature drop. There is then the latent heat of fusion to turn it into ice; 79.72 cals per g of ice. All these calculations are in calories as it is a lot easier.
Say you try to freeze 1000g of water that starts at 10 deg C. You will have to 'lose' 1000 x 10 = 10,000 calories to reduce it to 0 deg C. To then freeze it, you will then need to 'lose' 1000 x 79.72 = 7972 cals. Total is therfore 17972 cals. or near enough 18000 cals, as it is not going to be exact.
If you fill the trays with snow, you need to ram it down hard, leave it to get as cold as possible over a frosty night, then store it before it gets any warmer. |
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vegplot
Joined: 19 Apr 2007 Posts: 21301 Location: Bethesda, Gwynedd
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Nick
Joined: 02 Nov 2004 Posts: 34535 Location: Hereford
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shadiya
Joined: 02 Feb 2008 Posts: 1285
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Behemoth
Joined: 01 Dec 2004 Posts: 19023 Location: Leeds
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Mistress Rose
Joined: 21 Jul 2011 Posts: 15600
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shadiya
Joined: 02 Feb 2008 Posts: 1285
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Mistress Rose
Joined: 21 Jul 2011 Posts: 15600
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shadiya
Joined: 02 Feb 2008 Posts: 1285
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Ty Gwyn
Joined: 22 Sep 2010 Posts: 4563 Location: Lampeter
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Mistress Rose
Joined: 21 Jul 2011 Posts: 15600
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