Quote:
Originally Posted by DoubleF
the only way that maybe I could see it working is maybe if it helps to keep a frozen object solid for longer?
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Yes, that is exactly the point, it keeps things frozen longer.
Ok, let's see if I can share my understanding of the science. Grabbed some numbers from here:
https://weather.cod.edu/sirvatka/watertype.html
It takes 1 calorie of energy to increase the temperature of 1 gram of water by one degree. That is the same of any state of water; solid or liquid.
It takes 80 calories of energy to melt water from solid to liquid. That happens with tap water at 0 degrees, and with the salt water at -18 degrees.
Bringing a 4 litre bottle of tap water up from -18 to -1 takes 68,000 calories. And at -1 it isn't doing much to keep anything frozen, just "cold."
Bringing that 4 litre bottle of salt water up from -18 to -15 takes 332,000 calories. So almost 5 times the amount of external heat applied to the cooler. (Keeping in mind that in physics there is no such thing as "cold"- just adding or removing heat.)
That being said, bringing either bottle from -18 to +2 degrees will take the exact same amount of energy eventually. (400,000 calories.) However the peak absorbtion of that energy will be at a lower temperature with the salt water. Meaning that over a long weekend the cooler gets 150,000 calories of energy applied to it, the salt ice will still be around -16 but the tap water ice will be at 0. And assuming that was 50,000 calories per day, part way through day 2 the tap water will be at 0.
At the end of the day, I can confirm that I was thawing bacon before I could cook it on the final day, and at the end of the trip I returned the extra burger patties to my freezer while still completely frozen. I also ran into an issue of my coffee cream being partially frozen the first morning.