Joule-Thomson Coefficient pT

Hey guys,

I have question to Joule-Thomson Coefficient!

J-T Coefficient tells us the Temperature change of the gas by expansion prom pressure1 to pressure2.

As you can see in this table the J-T Coefficient depends on initial pressure and temperature.

When I have a closed tank, filled with Argon at 200 atm at 200 degC and I open the valve and let the gas expand, the pressure in the tank will drop with the time right.

Does it means that my J-T Coefficient will change (get better) by the time?!

Thanks for help!