Ok this is a physical one.
Temperature is just the total speed of molecule vibrations in an object.
Vibrations are movement. Movement needs energy. All things thrive to be in an energy neutral state, energy always disperses, disbalances are always balanced out.
This means that the natural state of objects is 0°K, the lowest temperature possible, no movement.
That is why you should fill up your fridge and freezer! The only energy you need is for removing heat that comes into the thing and would in turn transfer to cooler objects and warm them up.
But keeping things cool itself doesnt need any energy 🤯
And if you heat it up then less air comes in, and the incoming air will be cooled down faster (energy balanced out between low density air and high density things). So the overall temperature doesnt spike as much and less needs to be transported off.
Yesssss but technically cooling doesnt require energy XD just insulating heat
Which does not increase the more you want to cool, it only depens on the size and properties of the barrier (the fridge)
At least that makes sense for me
I think I understand the claim: the energy cost of keeping heat outside of a box should be proportional to the surface area, not how much stuff is in the box.
This is true; but only once the contents of the box are already cold. I think what it neglects is that the stuff you are putting in is not already 0 K (or your fridge temp), it is usually much warmer. So the fridge must work rather hard to pump all the heat you add back out. (Incidentally, the fridge has an even harder job if the volume of the fridge container is bigger, since there are more places for the heat to hide/cluster.)
We see the opposite with old fashioned fridges (an insulated box that you put ice into, and removed the water when it melted) or modern coolers. By making an insulated box, you make the interior become the average temperature of the stuff inside. To make the stuff inside cold, you must add something much colder to bring down that average, like a pack of ice. It’s pretty hard to get 0K stuff on earth, so many things to bump into, hence very hard to use refrigeration to get things down to 0K.
You might also be tempted by a selective insulator, that keeps hot stuff out but lets fast moving particles inside escape (so that the contents become cold). This is a classic thought experiment! Maxwell’s demon. It turns out that any such intelligent barrier will itself need energy.
In the off chance this involves the plan to load the fuck out of your freezer since it’s “free” if you overfill the fridge/freezer you are likely to interfere with the flow of cooling air causing cold spots and hot spots to form that will reduce overall efficiency
Interesting. Dont freezers also cool via conduction?
Well temperature goes from hot to cold so are you referring to warm food cooling from conduction of touching colder food?
Well warmth is flowing from the food to the cooling object via conduction
If it’s directly touching the walls it will decrease the efficiency of the freezer since initially the rate of resistance to heat transfer could have been represented by L/KA+ 1/hA with L being thickness of the wall of the freezer K being the thermal conductivity of the freezer wall and A being the surface area and h being the convective heat transfer of mostly stagnant air. In that case the effect of conduction through the freezer wall is a worse insulator than the transfer of heat through the air but by touching the item to the freezer wall you are trading that 1/ha for another L/KA with a negligible L so the resistance to heat transfer is also negligible.
That’s a lot of terms but you have experienced this before if you have a pan on the stove and you hold your hand above the pan it will feel significantly less hot then if you place your hand directly on the pan. If you have someone put a fan over the pan so there is a flow of air and then put your hand in the same place it will feel warmer since now you have air movement which increases your h term but it will still be significantly less hot then if you touch the pan.
I still might not be explaining this well but the math for it comes from the resistive model of heat transfer that while it has a lot of reciprocals I still find it to be the easiest to get an intuitive idea of what’s happening
In summary though from everything.
Empty freezer bad because the air inside leaves whenever you open it.
Very full freezer bad because it blocks flow of coolant causing hot spots and cold spots so needs to be kept much colder to make sure the hot spots don’t get too hot which causes more losses
Touching freezer wall bad because accelerates warming
Mostly full freezer good because the items work as a heat sink helping to keep a regulated temperature while allowing proper flow of coolant