Originally Posted by Panope
Adding to the above post:
Another reason having a full fridge (no air) may reduce power consumption
is that it reduces the amount of cold air that spills out of the space when the door is opened. This is probably a big factor when dealing with a front
loading fridge design, and a small factor when dealing with a top
loading design as the cold air tends to stay inside via gravity (cold air heavy).
Actually, there is very, very little heat, astonishingly little heat in the amount of room temperature air which would be needed to replace 25 liters of air which might spill out of a fridge like Mark's. The specific heat of air is about 1kJ per kg per degree K, less than 1/4 the specific heat of water
. And one liter of air at 15 degrees and at normal atmospheric pressure has a mass of only 1225 grams per cubic meter, or 1.225 grams per liter, nearly 1000 times less the mass of a liter of water
So as a result of all that, 25 liters of air at a given temperature has less heat in it than 7 milliliters of water at the same temperature. To put it another way -- if you put one single
warm Coke in your fridge, you have put more heat into it than if you spilled all the air out of it 43 times.
Net net -- don't worry about displacing the air in your fridge, and don't worry about the air spilling out of it.
The big advantage of top loading fridges is that if the door gasket
is not perfect, then there will be less exchange of air with the cabin
by convection. But a front loading fridge with a perfect gasket
will be hardly less efficient than a top loading fridge with a perfect gasket.