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Thermodynamics: why is freon a "good" coolant?

  1. Sep 9, 2015 #1
    I always thought that a working substance / coolant with a high heat capacity is better since it can take in more thermal energy. why then are some of the most common heat exchange fluid chemicals ones with low heat capacities?

    acetone and freon for example, are commonly used heat exchange fluids. But what makes them better candidates than water which has a higher specific heat capacity?
     
  2. jcsd
  3. Sep 9, 2015 #2

    Bystander

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    Is there another physical property that can be/is used for refrigeration/heat transfer?
     
  4. Sep 9, 2015 #3
    If you think about freon in a cooling system, then it is not a passive "heat exchange" fluid. It is supposed to evaporate easily in order to "capture" the heat from the hot object. The vapors are then condensed somewhere else to release the heat. I suppose acetone is used in a similar way. Like in the "drinking bird" toy.

    Edit
    Oh, bystander's post was not up when I wrote.
     
  5. Sep 9, 2015 #4
    oh right, forgot about that other half. so, low latent heat values for fusion and vaporization.
     
  6. Sep 9, 2015 #5

    Bystander

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  7. Sep 9, 2015 #6

    russ_watters

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    Actually, no, it isn't the latent heat of vaporization or fusion (not fusion at all). It is the temperature of vaporization. Air conditioners have specific temperature ranges for their heat source and sink, so the working fluid must be capable of doing its phase changes near those temperatures. So what is needed is a fluid that will vaporize at about 40F and condense at 140F, at reasonable pressures. Indeed, the same property that makes propane a useful stored BBQ grill fuel makes it a good refrigerant!

    A similar reasoning is why steam is good for heating.
     
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