Liquid refrigerant pressure and temperature

[Arvindaa]

Consider a sealed can of liquid refrigerant-134a in a room at 25 •C .Now if the lid is opened slowly and some refrigerant is allowed to escape, the pressure and temperature in the can start dropping rapidly.A thermometer inserted in the can will register -26°C when pressure drop to 1 atm. ,which is the saturation temperature of refrigerant-134a at that pressure.
Now my question is what causes to decrease the temp. of can .

 

[Greg Bernhardt]

Is this homework? Tell us how far you've gotten with the problem.

 

[Arvindaa]

From thermodynamics book by cengel and boles

 

[Mech_Engineer]

The basic answer is conservation of energy, as a gas expands it cools.

See this thread from 2011 on the subject: https://www.physicsforums.com/threads/why-do-gases-cool-on-expansion.470311/

 

[Arvindaa]

Acc. to above thread , can fluid gets cooled due to expansion but how it maintain its saturation temp. and pressure all the way.

 

[Arvindaa]

Thanks for giving above link I found answer in that.

 

[russ_watters]

The basic answer is conservation of energy, as a gas expands it cools.

See this thread from 2011 on the subject: https://www.physicsforums.com/threads/why-do-gases-cool-on-expansion.470311/

That's fine, but he's asking about the can of liquid, not the escaping air. The can of liquid cools because when the pressure inside the can drops, it starts to boil, nearly instantly dropping it to its boiling temperature at that pressure.

The Joule-Thompson effect is a bit confusing and tends to come up in places where it doesn't apply, such as this and air compressors. Joule-Thompson is about expansion of gas. This (and air conditioners) reduce pressure and boil liquids.