Quote:
Originally Posted by GGG
Wrong equation.
CO2 is mostly liquid in the canister at the Vapour pressure. So the problem with overfilling and then raising the temperature isn’t the change in vapour pressure due to temperature.
Instead if there is no gas space for the liquid to expand into the pressure rise will be driven by liquid thermal expansion. At that point the pressure rise equation is essentially dT*alpha/compressibility of CO2.
This is one of the two common mistakes among people who refill the camping butane / propane mix canisters.
One mistake when re- filling those is not understanding that the pressure in the partially filled canister is the vapour pressure of the mixed gas. So people will say they won’t fill it up all the way if they use propane instead of butane/propane mix. Since Propane as a higher vapour pressure as soon as you start filling you bulge the canister.
The second is the above mistake of assuming the pressure in then canister when overfilled is driven by the vapour pressure of the fluid as opposed to liquid thermal expansion. 10 degrees is easily sufficient to over pressure the butane cylinders. Now with CO2s vapour pressure being about 6MPA you will have more design margin on the canisters but I’d still be very concerned with overfilling.
|
For the average person solving for resulting pressure from a temperature increase gets the point across. Don't need to get into process simulations and vapor pressure calcs for multiphase hydrocarbon blends.
For those interested in more info on the exploding tanks (BLEVE)... here:
https://en.wikipedia.org/wiki/Boilin...apor_explosion