The fridge post incited sufficient controversy. We start to come up against matters of theory vs. practicality. Here are two:
1) “Why not put the fridge in the coldest place in the house, instead of the warmest?” This is a good question. I can see two competing arguments: (a) It makes no sense to store things you want cold, like beer, in a room you want warm, like the kitchen; but also, (b) It seems to make no sense to keep a net-heat-producing appliance, such as a fridge, in a room where the heat it gives off of no human use, such as an unheated spare bedroom. We can all agree that cold things should be kept in cold places, and warm things in warm places– but the fridge is both cold and warm at once. So where does it belong?
My instinct on theory is to stick with the fact that the fridge is a net-heat-producing object, not a stably-cold object, so long as it’s running at all. And thus it should stay in the kitchen. If you have a place where it doesn’t need to run at all, you don’t need a fridge at all– you just need some shelves. So the whole problem goes away.
But, practicality outweighs theory on this one anyway. First, it’s obviously not so practical to have the fridge far from the kitchen (though if that was the only argument, I’d overrule it.) More importantly, it seems the average fridge/freezer combination isn’t designed to function properly in much-colder-than-usual-room-temp. See here. I can attest, in fact, that this is true: in the weeks when I had my kitchen in the range of 48-50F (9-10C), I struggled to find settings for the fridge that would keep the freezer contents frozen, without freezing all the veggies in the fridge. So. I am settling on the idea that, if you’re going to own a fridge, it’s ideal to keep it in a place that is occupied by humans, and neither too warm nor too cold. Which seems to be my kitchen.
2) This debate about whether throwing fridge-temperature water back outdoors is a waste of heat, or not. Gets mind-numbing. Gets into the difference between heat and temperature, which aren’t the same. In fact, bringing a bucket of icy water (or even ice) in from outdoors will simultaneously cool the house and add energy to the house. Amazing, but true, and due to the different heat capacities of air and water (and other materials). A liter of water and a liter of air, for example, might be at the same temperature– but the amount of heat they contain is enormously different, by a factor of over 3,000. In other words, letting the liter of water cool 1ºF will release over 3,000 times as much heat (calories, kWH, BTUs) as letting the liter of air cool the same 1º.
So, in terms of contained heat, swapping a 2L bottle of fridge-temp water for 2L worth of outdoors-temp air is muchmore significant than swapping equivalent volumes of air at those temperatures. Even swapping 2L of cold water for 2L of hot air is a bad deal, heat-wise. In fact, by my [very rough] math, to break even on the swap you’d need to get 2L of air that was approaching the surface temperature of the sun (just very roughly). Good luck finding that (and if you can, I don’t advise putting it in a soda bottle.)
Here’s another way of thinking about it. Suppose I offer you an attractive five-ton piece of solid iron which you can put in your house for the winter, or until you tire of it. This hunk of metal comes to you at at temperature five degrees lower than your current indoor temperature. It will of course have to displace an equal volume of your room-temp air when we install it, but otherwise, there is no cost to you. So– do you want it? (For reference, iron has a heat capacity about 3/4 that of water, and 2,700 times that of air.)
J. and I discussed this last night. She refused my offer. I said I’d gladly take it if she didn’t want it. This, I think, because we were considering the situation from two different angles: heat (me), and temperature (J.)
J’s argument: the relatively-cool meteorite, with its enormous heat capacity, will draw heat out of the air and all the other objects in her house. Once they reach a new equilibrium, the overall house temperature will be lower than she started with, which makes her unhappy. If she wants to get back to her starting temp, she’ll have to supply more heat to re-warm the house (and the iron), which also makes her unhappy. So, she rejects the plan, on valid grounds.
My argument: the meteorite, as is, contains a vast quantity of heat– certainly more than the warm air it will displace, and quite possibly more than the entire rest of my existing house structure and contents combined. It’s like free money. So long as I don’t dispose of the iron when it is warmer than I accepted it, it won’t cost me anything. And if I wait till the whole system (house and iron) has cooled below the original iron temperature, then I will have sucked some free heat out of it. All I have to do is remember to roll the meteorite out of the house when it’s as cold as possible– perhaps when I return from a week of vacation and the heat has been set to minimum for a week.