Is the salt cooling method a myth?

[JuliaAnne2018]

I'm going to see about getting a larger generator asap. At least it gets cooler here this time of the year. I was doing research 2 months ago on homenade air conditioners. Is the salt theory true or a myth?

Supposedly, salt melts water at a colder temperature but keeps the water cooler for longer.

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[highdesertranger]

salt water freezes at a lower temp. I believe ocean water it's 28.5°. some one else needs to answer your other questions I am not sure exactly what your asking. highdesertranger

 

[Zil]

Salt doesn't lower temperature. It allows the water surrounding the ice to be colder than 32f. The water salted, or not, will never be colder than the ice you are using.

 

[John61CT]

What we call ice is made from plain water.

But a salt solution freezes at a lower temp.

It is the phase change from solid to liquid that absorbs a huge amount of energy, aka makes things cold.

There are specialized eutectic solutions, designed for higher or lower freezing/melting points.

So a holding plate designed for a 12V freezer should contain a different solution than one for a fridge.

Also google "polar tubes"

 

[JuliaAnne2018]

Guy/gfish,

I think your reply was meant for my other post? But yeah, I guess they call the lithium ion pack a "generator" because it has AC plugins, USB ports, etc. It is 300 watts. I can't remember how many hours I think for at least a day or two. It only takes 9hrs to charge in the sun.

It might not be powerful enough for a large AC, but if I could find one that runs on 300 watts, that's what I'd want. I might end up having to buy a bigger one.

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[JuliaAnne2018]

As far as the salt issue, when it comes down to it, does it really help keeping things cool at all? I tested it a little bit about two months ago. It didn't seem to make a difference.


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[Trebor English]

When a pound of plain water ice melts it absorbs 144 BTUs.  If you take a pound of water and add salt it then weighs more.  When you freeze that it still absorbs 144 BTUs when it melts.  It does the melting at a lower temperature which could be important.  In cooling the air in a van that wouldn't be noticed.

 

[JuliaAnne2018]

I tested it last time in my apartment living room in 90-degee weather. This time I'm going to test two homemade ones plus an Arctic Air in my car. The last time I was on the road, the one thing I think helped was blankets over my windows. I want to get UV covers if they willhelp. I was driving alone and it was hotter than H before turning on my AC. Even hotter a month ago. It's colder up north though but still hot.

So the salt: would it actually cool me down? I haven't had my dog in the car, by the way, most of the summer.

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[Zil]

A fan blowing across any ice would cool you down. Before Mr Carrier, hospitals in the south used ice to cool the air.

 

[John61CT]

Please link to the specs for your "solar generator".

300W is an energy rate, not related to the energy stored (watt-hours or AH).

So that 300W may mean "the powerpack supports some devices (loads) up to 300W **usage**"

which may be the max rating of the included / built-in inverter

Or if solar panels are included, 300W of rated energy **input** for loads + charging would be pretty respectable, and make the misuse of "generator" a bit less ridiculous.

However in **either** case if an aircon unit existed that could be powered within 300W, in hot weather it would only keep 2-3 cubic yards of very well-insulated space cool.

Perhaps look at the ones designed for dog houses?

 

[John61CT]

Also please explain what you mean by using salt to cool you down, maybe a link to where you got the idea?

 

[Spaceman Spiff]

 . . . Is the salt theory true or a myth?

Supposedly, salt melts water at a colder temperature but keeps the water cooler for longer.

Short answer: No.

Salt added to water ice makes it absorb heat (melt) faster, but does not add to the specific heat capacity (ability to absorb more heat).  You add salt to the ice in an ice cream maker to make the process work faster.

Salt water freezes at a lower temperature, the more salt the lower the temperature, but it has a lower specific heat capacity so it actually cools less.

 

[John61CT]

Salt water also freezes at a lower temperature.

Hence polar tubes working better than plain ice at keeping foods safe.

Of course you need a powerful freezer to take them down as cold as possible before transferring to a cooler.

Good for an ice-powered space cooler as well.