wedivebc:Right of course. If the supply cylinder is getting cooler then the receiving cylinder is getting warmer. My point is no heat (energy) is being added to the sytem, just a change in temperature due the the movement of heat energy, whereas a compressor adds heat to the system due to compression (Guy-Lussacs Law mentioned above)
The heat generated by compression is the adiabatic heating. Even though the tank cools after being filled, Lussacs law and charles law are still satisfied.
It is my belief that less temperature increase occurs when transfilling than when compressing since no heat energy is added to the system when topping up from banks.
The definition of an adiabatic process is that heat transfer to the system is zero.