If a running refrigerator is left open inside a close closet, why does the closet warm up?


Sora asks:

Let’s say you put a running refrigerator inside a closet, close the closet, open the refrigerator door, why does the closet warm up?

I know it has to do with thermodynamics, and how fast the refrigerator can cool the air versus how hot is the surrounding air. No equations necessary, just why you think it’s happening. Thanks!
Lots of good explanations, Thanks everyone!
Lee_: Yes It’s Mandela with Laila Ali 🙂
Rob S: No I did not try it 🙂

Best answer:

Answer by Zach
A refrigerator is a heat pump. By using some pretty nifty physics with fluid expansion it draws heat from the inside even though it’s already cold and releases it to the outside environment.

If you open the refrigerator door inside the closet then the system will eventually reach an equilibrium point between itself. The heat in the closet will be generated solely from the fluid pump on the back of the fridge at this point (which will be pretty hot from running nonstop!)

15 thoughts on “If a running refrigerator is left open inside a close closet, why does the closet warm up?

  1. Because when the refrigerator door is closed, the air inside is isolated from the temperatures outside of the fridge. The refrigeration unit cools air and blows it inside the compartments, while blowing the heat outside.

    When in a closet, you’re creating a hot box for the fridge to be in because that cool air is meant to keep only the volume of space inside the unit at a certain temperature. A refrigerator doesn’t have 100% efficiency to begin with, so it throws off the balance even worse when you 1.) increase the space you expect to cool, 2.) decrease the amount of space in which the heat can disperse, and 3.) share that same space!


  2. Hi,
    Is That Mandela in the photo?.
    The heat is coming from the pump at the back of the fridge, and also from the fluid in a copper coil/pipe running at the back and through fridge compartments.The pump pushes this fluid in the coil/pipe running through some fins. Just like a car radiator. The fluid is the one extracting heat from the fridge and the fins in turn get rid of the heat into the closet.
    The open door of the fridge is just allowing more warm air into the fridge and causes the cooling system of the fridge to work much more than normal. This causes more heat to be generated, hence the warming up of the closet.
    Therefore the heat is coming from the running fluid in the copper pipe and the motor of the pump. The closet is warming up because the air is restricted in a small space.

  3. Actually, it’s simpler than that.

    On the back of a refrigerator are the condenser coils. Their job is to dissipate the heat that was on the inside of the refrigerator. This phenomena is rarely noticed about a refrigerator because no one has the occasion to experience the heat that exists behind it.

    It’s easy to think that a refrigerator is just a magic box with cold inside but the cold is created by drawing the heat out of the inside. And the heat has to go somewhere.

    With the fridge in the position that you propose, you might think that it could eventually cool itself down but due to inefficiencies, the electricity that is added to the situation does work that heats up things.

    That is, in the closed system of the refrigerator being in the closet, electricity is added and that has to drive the temperature up.

  4. I would think, because of the hot air that comes out of the back. A refrigerator is made to cool its self not its surroundings when it is open.

    P.S. Did you try this?

  5. In theory, the adiabatic warming of the compressor should equal the adiabatic cooling of the nozzle. But … any mechanical system has a lost of energy in friction. The compressor’s motor is not frictionless.

    Therefore, there is a slight increase of temperature in this closed system.

  6. As is the case with air conditioners, refrigerators work by exchanging heat. The inside of the refrigerator is cooled by drawing that energy into the coils on the outside (usually the back) of the refrigerator and dissipating it in the form of heat.

    Being a small space a clothes closet will store the heat, even though the refrigerator door has been left open. The cooling is mainly concentrated inside the refrigerator although some cold air will dissipate in the closet as well.

    The cold air should sink to the floor area of the closet, while the hotter air should rise toward the ceiling.

    This would be an extremely silly thing to do, which I suspect you already know. The refrigerator would be competing with itself to heat and cool the air in the closet. The electric company would be the only winner of this competition.

  7. Lots of good answers above, but here’s a simpler one.

    It takes energy to run the refrigerator. And yes it normally cools downs the inside of the refrigerator. However, the energy that it takes to create one unit of “cool” generates enough heat (from the compressor, usually located on the bottom and vents the heat out the back) to cancel out the “cool” and then some. Therefore, if you put a refrigerator in a closed closet, the net effect is excess heat.

    Remember the electricity that is used by the refrigerator has to go somewhere. It’s in the form of excess heat.

    There are 2 examples of laws of thermodynamics here. 1) energy cannot be created or destroyed – hence the electricity used manifests itself as excess heat. 2) entropy is always increasing and in this case, it’s in the form of excess heat in an enclosed space.

  8. Well wouldn’t that be a waste of a lot of energy, an open refrigerator in a closed closet.

    Zach has a point, in the 2nd law of thermodynamics it says that if a cold body and hot body are brought together that the cold body would experience a warmer change and the hot body vice versa. (making an equilibrium of heat exchange).
    But what he fails to mention is that these two systems…(the fridge and the closet, will not reach an equilibrium of hot and cold, becuz both bodies are either warm or warming the room, there is no coolant in this example).
    A refrigerator doesn’t lower the temp of the bodies inside it, but rather draws the heat away using an evaporating gas (refrigerant). The idea that the open fridge is going to cool the closet is not gonna happen, becuz the heat that is being extracted from the fridge is being bought right back into the closet, elevating room temperature with in the closet.
    This would be like having a a tube sucking water out of your room, only to have the the other tube end in the room.

    Not to forget to mention the fridge working extra hard to cool itself, thus producing more excessive heat from the back and further elevating the room temperature.lol

  9. If the motor is running the fridge will eventually warm the closet. It may cool for a little while but in a matter of time it Will warm

  10. The compressor gives off heat .
    By enclosing the Refrigerator in the closet , you have no air
    circulation or air exchange , so , it builds up heat .

  11. first of all the back of the fridge releases hot air but air has the density to escape something such as a closet. The real reason is the light bulb inside is only on when you open the fridge. A light bulb will let of a lot of energy and when energy is released it will turn into some other form of energy. In the case of light thermal (heat) energy will be the outcome. in small a space like a closet a light bulb will heat faster than a fridge can cool. like a heater. it takes some time to heat a room but if you put a blanket over it making the space smaller it will be hotter in the blanket faster

  12. It may cool some air temporarily for a short period of time but in the long run an open fridge just isn’t a fridge (it won’t work as a cooling machine) the surrounding air will warm up from the rear or the fridge trying to cool down an entire closet which just won’t work

  13. If you’ve ever noticed, the back of the fridge puts out hot air (by-product of the cooling system). So my guess is, when you open the fridge door, you make it work its little refrigerator butt off trying to cool the closet, which means it puts out more hot air from the back vents, which makes it work even harder to cool the closet, and so on, and you end up with a very warm closet.

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