experimental design

[superduper12]

---

Members don't see this ad.

please explain this sentence.

"the air coming out a balloon feels cooler than the surrounding air, even if the balloon has had plenty of time to equilibriate its internal gas temperature to the surrounding air temperature."

I'm thinking in terms of PT phase diagram and that pressure can change at a constant temperature...so why is the air cooler?

 

[kupakid]

please explain this sentence.

"the air coming out a balloon feels cooler than the surrounding air, even if the balloon has had plenty of time to equilibriate its internal gas temperature to the surrounding air temperature."

I'm thinking in terms of PT phase diagram and that pressure can change at a constant temperature...so why is the air cooler?

It really has nothing to do with PT phase diagram. (FYI PT diagram is only valid when you have constant volume and moles). It is called convection. The air is not "cooler" as you mentioned. The air temperature is still the same. But, when you put your hand on the blowing air, it "feels" as if the air is cooler because a moving air will take away more heat from your skin surface.

 

[superduper12]

"What is the Joule-Thomson effect? When a non-ideal gas suddenly expands from a high pressure to a low pressure there is often a temperature change. Officially, the ratio of ΔT/ΔP is known as the Joule-Thomson coefficient. "

http://www.earlham.edu/~chem/chem341/c341_labs_web/joule_thomson.pdf​