Why ideal gases are not used in refrigerator?

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Discussion Overview

The discussion revolves around the reasons why ideal gases are not utilized in refrigeration systems, focusing on the properties of refrigerants like hydrofluorocarbons and the characteristics of ideal gases compared to real gases.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant notes that hydrofluorocarbons are used in refrigerators due to their low specific heat capacity and low liquid/gas transition point.
  • Another participant questions the existence of an ideal gas, particularly around the condensation point, and seeks clarification on the definition of an ideal gas.
  • A participant suggests that noble gases like helium and neon, or even natural air, could be considered ideal gases and questions their applicability in refrigeration.
  • It is proposed that any real gas can be used in refrigeration as long as it remains below the critical temperature and above the melting point, but practical considerations dictate the use of safe and manageable gases with appropriate boiling points.
  • One participant emphasizes that ideal gases cannot be used due to their lack of intermolecular forces, which are crucial in refrigeration processes.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of ideal gases in refrigeration, with some arguing that real gases are necessary due to their properties, while others explore the theoretical use of ideal gases.

Contextual Notes

The discussion highlights the importance of temperature ranges and the economic factors influencing the choice of refrigerants, as well as the limitations of ideal gas behavior in practical applications.

Who May Find This Useful

This discussion may be of interest to those studying thermodynamics, refrigeration technology, or the properties of gases in engineering contexts.

kthouz
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I read somewhere that a special fluid, called hydrofluorocarbon, is used in refrigerator. It carries hot temperature from the refrigerator and put it out. They says that it has a low specific heat capacity and low liquid/gas transition point (room temperature).
Now my question is why ideal gas cannot be used for such a task?
 
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First of all - have you ever seen ideal gas?

Especially gas that would be ideal around condensation point?

What is a definition of ideal gas?
 
Nice answer Borek! I appreciate it.
But what if we assume noble gases such He and Neon or even natural air to be ideal (as we do always), can these be used in refrigerators?
 
It all depends on the temperature range and economy. The way I see it any real gas can be used (as long as we are below critical temperature and above melting point), but for practical purposes we use gases that are safe and easy to work with. That means they must have boiling point around room temperature otherwise you need a very high pressures for condensation and it makes the refrigerator absurdly expensive.

Note, that a lot depends on the temperature of the fridge content and surroundings.

Still, ideal gas can't be used by its very definition. Ideal gas doesn't have intermolecular forces which play a very important role.
 
thanks Borek. Now it makes more sense.
 

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