chilling tablets

Discussions about US MREs and other US rations
barzongak
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chilling tablets

Post by barzongak » Sun Feb 17, 2008 3:18 pm

dear friends,

i have heard about chilling tablets that every soldier can drop it in a glass
of water or beverage and drink it cold .

does anyone have information about it.

thanks

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Lifesaver
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Post by Lifesaver » Sun Feb 17, 2008 3:29 pm

What country is using these? I have not seen this item in American rations.
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Treesuit
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Post by Treesuit » Sun Feb 17, 2008 4:40 pm

Yes, which country is using these? I haven't seen them here or in any of the MRE's.

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Big Galloot
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Post by Big Galloot » Mon Feb 18, 2008 12:08 am

We need to spend a little time reviewing the Laws of Thermodynamics.

1. Entropy demands that any chemical reaction must produce heat, so a pill cannot "make" cold by a chemical reaction.

2. Any miniaturized refrigeration device would need a means of shedding the heat drawn out of the drink. Because, the device would be immersed in the drink, the only choice would be to "store" the heat internally. This is not possible at our current level of technology. When it does become available, they are not likely to use it to cool drinks.

3. It is possible to make a pill of dense material cold enough to chill a drink, say by cooling a nickel-silver tablet in liquid nitrogen and immediately immersing it in the drink, but it would be an order of magnitude more efficient to use the liquid nitrogen to make ice which has a higher specific heat capacity than any non-poisonous alternative. And ice is easier to carry around than liquid nitrogen.

4. Last, but not least, the time required to cool a drink would be a direct function of the available surface area cooling it. It would take hours for an aspirin sized tablet to chill a drink.

I choose to remain skeptical.
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kman
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Post by kman » Mon Feb 18, 2008 12:27 am

Big Galloot, so how does an ice pack/cold pack work? Something like this:


Image
Could you just activate one of these packs, drop it in your beverage, and wait for the frostiness to appear?

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dirtbag
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Post by dirtbag » Mon Feb 18, 2008 12:43 am

It's been done. Sort of... Kinda...
http://www.pist.ca/article.php/23cold
Using evaporation !
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Big Galloot
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Post by Big Galloot » Mon Feb 18, 2008 9:22 am

Kman -

As I said, entropy demands that every chemical reaction produces heat. You may rightly assume that these people will end up paying a hefty fine for violating the laws of thermodynamics.

My bad, I was assuming a closed system. Every endothermic reaction has an exothermic partner, entropy holds true over the entirety.
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deanopilot
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Post by deanopilot » Mon Feb 18, 2008 7:54 pm

Ammonium Nitrate and Beer anyone? How's that for a frosty idea?
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barzongak
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Post by barzongak » Tue Feb 19, 2008 1:12 am

I have heared it about american soldiers in iraq.

Baldy
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Post by Baldy » Tue Feb 19, 2008 1:58 pm

If this technology exists, surely they should use it to make troops invisible to thermal imaging equipment?

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