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  • cal3thousand commented on chopping block farm's instructable Forever and Ever Ice Pack2 weeks ago
    Forever and Ever Ice Pack

    Not exactly. The salt water take on additional cold due to a couple factors, BUT will melt faster and provide usable cold for less time, which is not practical for food storage.Here's a great and full explanation I found elsewhere:The heat absorbed will be equal to the latent heat of fusion plus the specific heat capacity of the water (or ice) multiplied by the mass multiplied by the change in temperature. In the case of the salt ice, the specific heat capacity of water would be the one to use, whereas the fresh water ice will undergo its temperature change in the frozen state. The specific heat capacity of ice is about half that of water, so it would seem there may be a slight advantage to your scheme. Slight, because most of the heat absorbed will be in the form of latent heat of fusi...

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    Not exactly. The salt water take on additional cold due to a couple factors, BUT will melt faster and provide usable cold for less time, which is not practical for food storage.Here's a great and full explanation I found elsewhere:The heat absorbed will be equal to the latent heat of fusion plus the specific heat capacity of the water (or ice) multiplied by the mass multiplied by the change in temperature. In the case of the salt ice, the specific heat capacity of water would be the one to use, whereas the fresh water ice will undergo its temperature change in the frozen state. The specific heat capacity of ice is about half that of water, so it would seem there may be a slight advantage to your scheme. Slight, because most of the heat absorbed will be in the form of latent heat of fusion.Heat capacity - Wikipedia, the free encyclopediaHowever there are also practical considerations. If you are using your ice pack to keep food and beverages cold in a cooler, the salt ice is a bad idea. It will probably freeze your food and drinks, then after it has melted, it won't do much good and the food will quickly warm up. Whereas the fresh water ice will keep the food and drinks at 0C (32F) for long periods of time, which is ideal. Also, since the interior of the salt ice cooler will be at 0F for a long period of time, the cooler will absorb more heat due to the greater delta-T across the insulated walls of the cooler.If you are using the ice to keep ice cream frozen, then the salt ice would probably be a good idea.

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