In an effort to cool a kitchen during summer, the refrigerator door is left open and the kitchen door and windows
Answers
In theory, this sounds like it should work, because the compressor in the refrigerator operates much the same way as a standard room air conditioner. In practice, though, there is one key difference between the fridge and the AC:
Where does the heat go?
The first and second law of thermodynamics indicate, among other things, that energy is never created nor destroyed; it can only be moved to another location or transformed into a different type of energy. This implies that to make something colder, you must remove heat (a form of energy) by moving it or transforming it into other energy.
In practice, moving the heat is generally the simpler option. AC does this with a substance known as a refrigerant. To put it simply, a refrigerant absorbs heat energy from its surroundings under certain conditions and emits it back into its surroundings under other conditions. (That’s an incredible oversimplification of the thermodynamics involved, but it’s sufficient for this explanation.) This process enables AC to pull heat from the air in one location and then spit it out somewhere else.
This is the key factor: the heat isn’t destroyed or stored, but moved. To make one thing colder, you must make something else warmer. The heat has to go somewhere.
Building air conditioning vents the heat pulled from the inside air to somewhere outside the building. This is why AC units are located outside (or, in the case of window AC units, set in an opening in the wall so that most of the unit is outside).
Kitchen refrigerators, though, are normally not so located. They vent the heat out of the refrigerator (usually out the back), but not out of the building or even the room. The intent is to remove heat from the space inside the refrigerator, not from the room in general.
You should be able to see where this is going: since the refrigerator doesn’t send the heat outside of the room, keeping the door open simply means the heat removed from the area near the door will simply be pushed back into the room on the other side of the refrigerator, from where it will flow back into the area being cooled outside the open door. The distribution of heat in the room has changed, but the room as a whole will not get any cooler.
In fact, if you leave the door open for more than a very brief moment, the room will actually get warmer overall. Another implication of the laws of thermodynamics is that work (defined as a process that uses energy) is never 100% efficient, so there will always be some amount of energy that is used but does not contribute to the work’s results. Normally, this energy escapes the system as heat.
In this case, the energy being used to do the work is electricity, which is transformed into mechanical energy in the motor that drives the pump that keeps the refrigerant moving through the cycle that moves the heat. A small amount of that electrical energy becomes heat due to friction in the motor, and that heat makes its way into the system’s environment. The longer you leave the door open, the warmer the room will get.
Now, with all that stated, I will come out and directly challenge the assertion, made by another answerer here, that it is “never” possible to cool a room by opening a refrigerator door. If you set up the environment correctly, you absolutely can cool a room this way. You simply have to arrange things so that the heat is vented to outside the room. This could possibly be done by, for example, mounting the refrigerator in the wall with a seal around it to keep the exhausted warm air out of the room.
You probably wouldn’t want to use a refrigerator this way, though. Its motor and compressor are designed to properly cool the small volume of the fridge and freezer interior. Even though you probably wouldn’t want to cool the room to the temperature of the fridge interior (roughly 4–5° C), an entire room, even a small one, is a much greater volume. You’d be overworking the motor horribly, using a lot more electricity than an appropriately-sized AC unit, and generating a lot more excess friction heat that the compressor then has to also try to extract from the air. You might even burn out the motor entirely.
To sum up, while you definitely could cool a room this way, with a lot of effort and the right modifications, you just as definitely shouldn’t do it.