mm wrote:

We all hear that keeping the fridge door open a long time lets the
cold out, but how long does this really take?

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