Thermodynamics: why is freon a "good" coolant?

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    Coolant Thermodynamics
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Discussion Overview

The discussion centers on the properties that make freon and other low heat capacity fluids effective coolants in thermodynamic systems, particularly in refrigeration and heat exchange applications. Participants explore the relationship between heat capacity, latent heat, and the phase change behavior of these substances.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions why fluids with low heat capacities, like freon and acetone, are preferred over water, which has a higher specific heat capacity.
  • Another participant inquires about other physical properties that might be relevant for refrigeration and heat transfer.
  • A participant explains that freon is not a passive coolant; it must evaporate easily to capture heat, and mentions acetone's similar behavior in applications like the "drinking bird" toy.
  • There is a mention of low latent heat values for fusion and vaporization as a factor, though this is later contested.
  • One participant clarifies that the relevant property is the temperature of vaporization, emphasizing the need for a fluid that can vaporize and condense at specific temperature ranges suitable for heat exchange systems.
  • The discussion includes a comparison to propane as a refrigerant and steam's effectiveness for heating, suggesting that phase change properties are critical in these contexts.

Areas of Agreement / Disagreement

Participants express differing views on the importance of heat capacity versus latent heat and temperature of vaporization, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Some assumptions about the properties of fluids and their behavior in thermodynamic cycles are not fully explored, and the discussion does not resolve the complexities of how these properties interact in practical applications.

iScience
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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?
 
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Is there another physical property that can be/is used for refrigeration/heat transfer?
 
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.
 
oh right, forgot about that other half. so, low latent heat values for fusion and vaporization.
 
iScience said:
, low high latent heat values for fusion and vaporization
 
iScience said:
oh right, forgot about that other half. so, low latent heat values for fusion and vaporization.
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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