I think the difference is that I was assuming an isochoric process, since a tank of fixed volume held the process. Maybe this is not the case? Either way, it should be noted that in my case I am just looking for a valid approximation, so I do not wish to model a differential problem. I have been...
Consider a problem where a tank holds compressed natural gas, compressed to approx. 250 times atmospheric conditions.
Now release the tank valve letting some of the gas out.
Assuming a small timestep, I can approximate the energy lost as 1/2 mv^2,
where m is the mass released during the...