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I just graduated and a mate moved into a flat (none of us are physicists by the way). So, were graduates, we got a new flat, and were broke.

So, were now having a debate on how to keep a fridge cool... well, cooler. I suggest that a fridge full of water will keep the food colder, as objects get cooler when water evaporates, (like when we sweat). He says that the fridge just has to do extra work to keep the water cool, but I said it doesn't matter as it's already colder when it enters the fridge, and it's properties should mean that the overall effect, is a colder fridge.

Another conundrum, if I AM right, is it more effective to store the water at the bottom, middle, or top shelves? Also, what size/shape should the water be in, should it be stored in glasses, bowls, or in the form of cloths, where the surface area can be distributed, a lot more widely.

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    $\begingroup$ Related: physics.stackexchange.com/q/61445 $\endgroup$
    – jinawee
    Commented Nov 17, 2013 at 16:03
  • $\begingroup$ @jinawee Please edit a post if you find it is appropriate. Don't expect a 2 rep user to know all the habits. $\endgroup$
    – Bernhard
    Commented Nov 17, 2013 at 16:26
  • $\begingroup$ Note that as the answer say the fridge is designed to keep a chosen temperature and will keep working until it reaches it. The more mass there is to cool the harder the fridge will work. On the other hand in the case of an electricity failute a full fridge stays cool longer than an empty one. $\endgroup$
    – anna v
    Commented Nov 17, 2013 at 19:03
  • $\begingroup$ @annav, only if you don't keep raiding it every twenty minutes :P $\endgroup$
    – pho
    Commented Nov 18, 2013 at 0:50

2 Answers 2

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You will make the fridge work harder in order to cool the water down. I don't think much evaporation will occur at that temperature, even though fridges are very dry (cool moist air simply condenses). However the dryness does contribute to floppy produce, hence, the crisper.

What would be better is to allow the fridge to work optimally. The fridge produces heat in addition to the heat it removes from your food, and it releases that heat in its radiator. If that flow slows down, the whole system backs up, thermodynamically speaking. Maybe dust off the radiators once in a while and keep them unobstructed.

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  • $\begingroup$ I think you would gain more by insulating the fridge walls better. Since once the inside has reached a desired temperature, the need for further cooling would be caused by heat transport from outside to the inside. $\endgroup$
    – fibonatic
    Commented Nov 17, 2013 at 20:09
  • $\begingroup$ And opening the fridge. $\endgroup$
    – lionelbrits
    Commented Nov 18, 2013 at 1:55
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An object becomes cooler when water evaporates off the object. When you sweat, the water (or perspiration) on your body takes the heat it needs to evaporate from your skin, and hence it makes your skin (and the rest of you) cooler.

The fridge is going to cool its contents to the temperature you have set it at, regardless of what you put inside it, so you're just increasing the amount of work it has to do when you add water to the equation, so your friend is right about this.

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