We were all admonished as children not to “stare into the refrigerator” and “decide what you want before opening the door”. Hogwash, I say.
The air has little to do with the total energy inside the system when the door is closed. It has little heat capacity, and most of it probably surges out through convection in the first 20 or 30 seconds you open the door anyway.
One for the Mythbusters?
Shhhh. My kids are listening. Now shut the fridge door!
But seriously, surely 98% of the heat capacity in the typically full unit is in the contents, not the air.
I’m not going to comment on the validity of that percentage, but it is definitely true that most of the heat is lost when the door is opened. But that isn’t to say you aren’t wasting energy by holding the door open longer than it should be. Not wasting energy is always better than wasting energy in my book.
It would take the same amount of time it took for all the contents, and the inner body of the fridge to cool, as it would to heat back up to room temperature. So, when you open the door, you let most of the chilled air out, but that is so tiny compared to what’s already chilled.
My guess is it only takes moments for the air to cool back down, once the door’s been opened, given a fully stocked fridge and its influx of new, cooled air by the fan. So, quickly opening – grabbing – then shutting the door, wouldn’t hold much of a difference than leaving the door open for even minutes. So, take your time.
Then again, there is the matter about the little light in there…
This doesn’t really match with my personal experience. If I open the door, the fan will usually kick on shortly after. If I close it fairly quickly, it seems to be on for only a short time, but if I leave it open for a couple minutes (say, I forget to shut it entirely), not only is the fan running for those few minutes (which is usually how I realize I left it open), but it seems to run longer after the door has been shut.
While the door is open and the fan is running, the fridge is circulating cool air, but losing quite a bit of it to the room. The sooner the door is shut, the less of this wasted cool air circulation.
Granted, we are not talking about massive savings, but, at the risk of using a hackneyed quote, we all know what Ben had to say about those pennies.
Personally, I’d rather not waste energy in areas where it can be so easily avoided.
The air inside is probably very dry, but the air outside may have a higher humidity.
This means it can carry marginally more heat.
It also means the potential for condensation or frost (and the need for dehumidification which requires energy). It’s not clear to me if this amount is significant.
In the case of actual iceboxes (the insulated boxes which required one to add ice to keep things cold) there was no machinery to pump that extra heat out, and so leaving the door open for long periods of time would indeed permanently deplete your supply of “cold”.
Perhaps the attitude is vestigal.
Sure, and at the same time, why not let the water run while you are brushing your teeth, or leave the lights on when you aren’t using them. :smack:
It may be a small effect, but it’s still wasteful, and teaching kids (or adults, it seems) that it’s OK to be wasteful is a bad idea, especially now that the US is making tiny steps to become energy independent.
No. The air inside the 'fridge has a higher humidity, generally, than the air outside. Unlike an air conditioner, which cools the air to much lower than the target ambient temperature, thus “squeezing” out excess moisture which results in a lower RH% when the air warms up again inside the room, a refrigerator cools the air inside to whatever temperature you have the thermostat set for and the RH% climbs until it reaches nearly 100% at which point you start to get condensation on the inner walls.
Most of the “cold” may be in the contents, not the air, but the air is the part that trigger the thermostat, which triggers the cooling system, which wastes the energy.
Your house is probably 70 degrees or so, the fridge stays close to freezing, say 35 degrees. When you open the door, 35 degree air will fall out and be replaced by 70 degree air. The fridge has some sort of thermostat that triggers the compressor, I bet it measures the air temperature inside the fridge. The more stuff you have in the fridge the sooner the compressor can get the air temperature inside there back to the desired value.
Didn’t I just say that?
