scubasean
Contributor
Hi folks:
what I know: Filling a tank heats the tank. Because the tank will later cool, the pressure will drop, due to PV ~ T , so you must fill the tank to a pressure that "looks" high, which will then be right once the tank has cooled.
what I don't know: What is the ratio between temp and pressure...For example, does the pressure drop 5psi per degree F? Also, how much will the temp of an empty tank (say....less than 200PSI in it when the fill begins) increase during filling?
So, what I'm after is really....My 80 is rated to 3300PSI, and I want to know how much it needs to be filled to in order to arrive at 3300PSI later, when it is at equilibrium, say at 70F or so...Seems like you'd need to go up 200PSI or so to get it right...
Finally, is it reasonable to expect filling stations to accommodate?
Thanks,
Sean
what I know: Filling a tank heats the tank. Because the tank will later cool, the pressure will drop, due to PV ~ T , so you must fill the tank to a pressure that "looks" high, which will then be right once the tank has cooled.
what I don't know: What is the ratio between temp and pressure...For example, does the pressure drop 5psi per degree F? Also, how much will the temp of an empty tank (say....less than 200PSI in it when the fill begins) increase during filling?
So, what I'm after is really....My 80 is rated to 3300PSI, and I want to know how much it needs to be filled to in order to arrive at 3300PSI later, when it is at equilibrium, say at 70F or so...Seems like you'd need to go up 200PSI or so to get it right...
Finally, is it reasonable to expect filling stations to accommodate?
Thanks,
Sean