Sodium acetate as a thermal buffer?

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Christophe
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Sodium acetate as a thermal buffer?




by Christophe » 29/06/10, 14:10

Recently I found a small heater (emergency) decathlon for about 5 €, I took it to do some thermal tests, it is based on sodium acetate and it is regenerative (of where my interest):

Image

Image

The 2ieme photo is not blurry is the product that is.

So I'm just wondering if we can regenerate the thing in the sun (even if it takes more time) ... because boil 15 minutes, the overall balance must be quite zero ... :?:

Good I crack the pellet? :?:
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by Christophe » 07/07/10, 15:51

I cracked the pellet 1h ago:

a) the reaction propagates very quickly: in less than 10 seconds the whole product becomes milky and hot (limit too hot given the current temperature)

b) it really heats up a lot

c) it's still hot after 1h

d) at the texture level, it looks like lemon sherbet, we clearly feel the crystals when we knead

I will now leave it in the sun to see if we can regenerate it this way.
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by Christophe » 07/07/10, 16:38

It is 30 min that the heater is in the sun (behind a glass on a dark surface) and it seems to work because it becomes much more fluid and we no longer feel the crystals ...

By cons it is still very cloudy ...

To be continued...
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by Christophe » 13/07/10, 19:00

Good it does not regenerate in the sun (without concentration), the T ° must be insufficient: there are still crystals ...
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by dedeleco » 13/07/10, 23:19

It's strange to want to warm up in a heat wave!

Basic Info to understand:
http://fr.wikipedia.org/wiki/Ac%C3%A9tate_de_sodium
Pouches sold as portable heat sources (heaters) are commercially available. These pouches contain a saturated aqueous solution of sodium acetate supercooled, the solidification temperature being 54 ° C for a solution 20%, which is well above room temperature. Pressure variation (by trituration) is not generally enough to cause precipitation. By twisting a metal plate inside the liquid, solidified acetate seeds are released which trigger crystallization and the solution becomes solid [6]. This transformation is exothermic, which means that it is accompanied by a release of heat, sufficient to provide comfort to the user. This solution is redone again by placing the pouch in very hot water; even while cooling, the sodium acetate remains in solution. It also makes it possible to create instant and hot ice by mixing the water and the acetate in an old saucepan.

Melting point 58 ° C (release of water from the trihydrate) [3]
T boiling Decomposition at 324 ° C to Na2O [3


So to liquefy, it is necessary to go up to 60 ° C but to provide the necessary heat to melt everything, and thus to wait a long time in the sun, rather strong, as in the Sahara !! But in the north, the sun is a little weak !!
Read also:
http://ssaft.com/Blog/dotclear/index.ph ... e%20Sodium
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by sherkanner » 14/07/10, 11:04

In a small transparent box to enjoy the greenhouse effect, in summer it must not be too difficult.
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by chatelot16 » 14/07/10, 11:22

with a parable the sun can make a high temperature and even screw up your plastic bag

the sun must be used to boil water: the boiling of the water limits the temperature to 100 ° C

the solar parabola is not the only solution: the vacuum sensor goes up very quickly to 100 ° C
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by I Citro » 15/07/10, 00:03

chatelot16 wrote:the sun must be used to boil water: the boiling of the water limits the temperature to 100 ° C

the solar parabola is not the only solution: the vacuum sensor goes up very quickly to 100 ° C
The flat sensors also ...
I recorded 139 ° C to the sensor a few days ago ...
The temperature in the CESI balloon sometimes reaches 89 °
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by chatelot16 » 15/07/10, 00:22

we agree the sun can boil water, so regenerate the chauferette

the real question is that this principle of heat storage is interresing for a big energy?
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by dedeleco » 15/07/10, 15:06

Reply-:
http://forums.futura-sciences.com/chimi ... odium.html

Re: Sodium acetate!?!
The enthalpy of formation of sodium acetate crystallized with 3 water molecules is -1603 kJ / mol. the sodium ion is at -240kJ / mol. The acetate ion is at -488 kJ / mol, the liquid water at -286 kJ / mol. So the crystallization reaction of your salt is:
Na + + CH3COO- + 3 H2O ---> NaCH3COO.3H2O
and this reaction gives off:
-1603 + 240 + 488 + 3 * 286 = - 17 kJ / mol
It is efectively exothermic, but not much


So what to heat salt 30 50 ° C without burning!
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