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How does coolant work?

  1. Jul 3, 2013 #1
    How does the cooling mechanism work in fridges? From what i have heard, it works by compressing frion and pushing it through a tube, because of the pressure and moving it through a tube it cools down.

    It still doesn't make sense can anyone help?
  2. jcsd
  3. Jul 3, 2013 #2


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    Compressing a gas makes it hotter (e.g. a bicycle pump). Expanding a gas makes it cooler (e.g. a can of compressed air). A refrigerator works by compressing a gas, then cooling that pressurized gas using a heat exchanger on the outside, then expanding the gas on the inside where it gets very cold and using another heat exchanger to cool the inside. The cycle then repeats.
  4. Jul 3, 2013 #3
    There is a little more to it than this. With a typical refrigerant like freon, during cooling the gas in the external heat exchanger, the refrigerant is actually condensed to a liquid. In the other heat exchanger, the refrigerant evaporates to a gas again as it removes heat from inside the refrigerator. So, the typical refrigeration cycle capitalizes on the latent heat of vaporization of the working fluid.
  5. Jul 4, 2013 #4
    That is also the reason why the outer heat exchanger tubes are narrower in diameter so that they would be suited for the different flow of the now condensed fluid.
    The inner ones that are into the fridge are larger and bigger in diameter.
  6. Jul 4, 2013 #5
    so if i get what everyone is saying, Freon is compressed intro a liquid, and forced through a tube which makes it lose energy, and then it is forced again through a grate of some sort to vaporize it without heating it up, which causes it to cool down even more because the molecules are farther away from each other right?
  7. Jul 4, 2013 #6
    Not exactly. After it is compressed, it is cooled by outside air (say at room temperature). This causes it condense at close to room temperature. Then, it is forced through a valve. The pressure on the other side of the value is much lower than on the upstream side. Also on the other side of the value is tubing that comprises the low temperature heat exchanger. The pressure in this heat exchanger is low enough to allow the refrigerant to evaporate (boil). Inside air from the refrigerator internal compartment (freezer) is being blown over the outside of the tubing, and the evaporating refrigerant removes heat from this air in order to evaporate. This causes the air within the compartment to be cooled.

    It's pretty much the same as a home air conditioner. Outside your house is a compressor to compress the refrigerant vapor, followed by a finned heat exchanger to condense the refrigerant. There is then a tube that carries the condensed refrigerant inside your house, usually to the basement where there is an evaporator in the combination heater/ air conditioner. House air is being blown over the evaporator tubing as it flows through the ductwork. This causes the refrigerant to evaporate and cools the house air. After the evaporator, there is a tube that takes the refrigerant back outside to the compressor.
  8. Jul 4, 2013 #7
    Chestermiller described the process in detail but in overall there are two radiators , one which gets cold during the process and attracts hot air and the other one which gets hot during the process and a fan blows away the hot air to cool it down.In smaller applications the second radiator is without a fan, just once the coolant has finished it's way through it it has already lost most of the heat that it transported from the first one.
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