# How long does it take for the cold air to leave the refrigerator

• posted on March 31, 2006, 2:17 am
How long does it take for the cold air to leave the refrigerator?
We all hear that keeping the fridge door open a long time lets the cold out, but how long does this really take?
If most of the cold air falls out in the first 10 seconds, and only 10 percent more in the next 10, and 3 percent more in the next 10, then after the first 10 seconds, there's really no rush.
Except I made up those numbers. Does anyone know any real numbers about this?
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• posted on March 31, 2006, 2:24 am
mm wrote:

I is going to take a few more variables to get a good number. Is the frig full, how full, does the stuff there repaint a lot of heat or loose it quickly? Fill that thing up with cartons of milk and you could leave it open a long time while loosing little, empty opening it for just five seconds would likely dump most of the cold air.
--
Joseph Meehan

Dia duit
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• posted on March 31, 2006, 3:38 am

The ambient temperature is another unknown.
Al
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• posted on March 31, 2006, 3:38 am
mm wrote:

All the stuff in there are cold. They all have to lose it to room temp. To lose all the coldness, it'll take a long while like a day? That is my guess. If it is empty, it may be different again.
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• posted on March 31, 2006, 6:39 am

One empirical chimney formula says cfm = 16.6Asqrt(HdT), so a 2'x2'x4'-tall 36 F fridge box with V = 16 ft^3 and A = 2'x2' top and bottom vents might fill with 70 F room air in 16/cfm = 0.02 minutes, ie 1.2 seconds.
But if it's full of thermal mass with lots of surface, eg milk cartons and jars, 70 F room air at 50% RH would keep flowing through the fridge box for a long time and condense water vapor onto the mass surface and add lots of heat to the fridge contents.
So it's best to keep the fridge nearly empty, given long door openings.
Nick
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• posted on March 31, 2006, 12:15 pm
Got alot of time on your hands don't you!
Tom