Why do tanks get hot when you fill them from higher pressure tanks?

[rjack321]

The equations don't care how quickly the process is done, only whether we add any energy. There are no "rate of change" terms in the gas laws. We are taking the gas in one tank and letting it expand into two.

You are adding energy to the receiving tank, that's why it gets hot. The donor cools off. Between both tanks and the whip there is no change in stored energy. The faster you fill, the colder the donor and the hotter the receiver will be. If you do it really slowly (days) the thermal isolation between the tanks provided by the transfill whip won't exist. And both tanks will remain at room temperature. Amazing huh?

So in the 0 psi tank going to 1500psi. What's that called?

 

[jimmyw]

So in the 0 psi tank going to 1500psi. What's that called?

Filling the empty tank by letting the high pressure air in the donor tank expand into the empty receiving tank. (As before, I continue to agree with the other part of your post).

 

[rjack321]

Filling the empty tank by letting the high pressure air in the donor tank expand into the empty receiving tank. (As before, I continue to agree with the other part of your post).

Yet no empty tank in history has ever gotten cold. Just maybe, the physics of filling a tank from a compressor or from another tank is really the same?

 

[halocline]

I do agree that the gas in the receiving gas is being compressed! But I also know that before it gets compressed, it started at higher pressure in the donor tank, and it has to expand to get into the lower pressure receiving tank. What is wrong with that statement?
If it expands, it cools. If it gets compressed later, it gets hot. If the recompression is less than the expansion, then the heating is less than the cooling. What is wrong with that statement?

Nothing is wrong with that statement. I think I said in my first post in this thread, it seems like years ago, that if you could measure the actual cooling and heating of the gas, you might find exactly that; less total heating energy than cooling. It's just that you are not measuring actual gas temp change, you're feeling the metal donor tank. That's warm because the gas inside it is being compressed.

Think about this; do everything the same except don't feel the donor tank. Go watch some TV while the tank is filling. I suggest a foghorn leghorn cartoon in which he tries to teach the widow hen's little boy how to play baseball:
http://www.youtube.com/watch?v=W0D6DZuTPsA

Then a few hours later come back and feel the tank. Nice and cool, eh? See, problem solved!

 

[Rick Murchison]

Just wait, you'll soon see the folly of your ways.

Tobin

I'm sure I'll be in good company Tobin
Rick

 

[RJP]

Filling the empty tank by letting the high pressure air in the donor tank expand into the empty receiving tank.

Ok, this so laughable that you're either just yanking our collective chains... or you never passed third-grade science class. Either way, it's time for you to stop now. I'll probably never know, however, as I'm tempted to put you on my "blocked user" list just to ensure that my own morbid curiosity doesn't keep bringing me back here.

 

[turt1e]

Some of you seem to be experiencing this...

When you should be doing this...

 

[rjack321]

Ok, this so laughable that you're either just yanking our collective chains... or you never passed third-grade science class. Either way, it's time for you to stop now. I'll probably never know, however, as I'm tempted to put you on my "blocked user" list just to ensure that my own morbid curiosity doesn't keep bringing me back here.

Oh please lord stay, I am aiming to stretch this out to 50 pages

 

[cool_hardware52]

I'm sure I'll be in good company Tobin
Rick

If you are part of the company it will be good. Take care.


Tobin

 

[redacted]

I have done a little research on jimmyw - well maybe. Would you believe he is a world champion fly fisherman? He has set records for getting the most trout to rise to the same fly and for getting the same trout to rise to the fly repeatedly. Congrats jimmyw - I think you have done it again in another pool