Fridge Full of Water?
Most recent answer: 10/22/2007
- James (age 19)
So I think Im gonna have to agree with your mom. Empty space in a refrigerator is inefficient.
Imagine a giant refrigerator full of nothing but cold air and one small hunk of cheese. Lets say that the fridge is holding the inside steady at 35 degrees. When you come along and open the door to get some cheese, the cold and warm air begin mixing together in the refrigerator. And
now that some air from the room has mixed with the cold air, the fridge is going to have to run again to pump that extra heat out of the refrigerator and back into the room. On the other hand, if all that empty space had been filled with jugs of water then thered be no room for warm air to get inside and replace some of the cold air. So itll basically
be the same temperature when you close it again.
The real key here has to do with how heat moves in air. Since air isnt very dense, its a poor conductor of heat. So, heat in air moves primarily by masses of warm and cold air mixing and trading places. In an empty fridge, lots of warm and cold air can change places when you open the door. In a full refrigerator heat can only enter by conduction of heat directly to some object thats inside (i.e. the cold broccoli isnt going anywhere, and it isnt being replaced with warm broccoli so itll have to be warmed up by conduction only). And... air is a poor conductor of heat.
I do agree that itll take more energy to cool down the
fridge when you first fill it with water jugs. But that
only has to happen the first time. Basically, by filling
the empty space, youre make a smaller refrigerator.
(published on 10/22/2007)
Follow-Up #1: refrigerator efficiency
(published on 09/19/2009)
Follow-Up #2: making refrigerators more efficient
- Jack B (age 33)
1) Excellent point. The empty jugs would also in effect make the refrigerator smaller, reducing the amount of cold air that escapes when you open the door briefly.
2) Sure. If you leave the door open a very long time the refrigerator will run full-speed all the time. Then when you close the door, it will need to run longer before getting down to its set temperature if the contents have more heat capacity. So in that very unusual sort of use, having jugs of water would actually increase the net energy use. Your empty-jug idea would work well both for normal use and for the rare case of doors being open for a long time.
(published on 01/14/2016)
Follow-Up #3: packing jugs in refrigerator
- Irene Kanzler (age 80)
The heat capacity will scarcely be affected by the foam peanuts, since they're mostly air. They will slow down heat exchange with the outside, which could marginally reduce enrgy use if the refrigerator is opened often.
(published on 06/26/2018)