Tough question

stonemason1

Hi

I wonder if anyone can help .What im trying to do is displace 2lt of water from a tank using co2.the plan is to use a 10 cubic cms co2 cannister that is under 900psi pressure i want the water to be expelled at a rate of 40psi.

Im not sure of the maths on this 900psi seems like a very high number for 10 cubic cms in a mosa 8g soda cannister.im trying to work out if the gas was expanded to a 2 lt size bottle what would the pressure be in that container ?

A huge thanks to anyone who can work it out

Professor_Fink

stonemason1 wrote: »

Hi

I wonder if anyone can help .What im trying to do is displace 2lt of water from a tank using co2.the plan is to use a 10 cubic cms co2 cannister that is under 900psi pressure i want the water to be expelled at a rate of 40psi.

Im not sure of the maths on this 900psi seems like a very high number for 10 cubic cms in a mosa 8g soda cannister.im trying to work out if the gas was expanded to a 2 lt size bottle what would the pressure be in that container ?

A huge thanks to anyone who can work it out

If the expansion is isothermal, then you have the product of pressure with volume at any point in time being constant. Thus P1 * V1 = P2 * V2. Now, we have 900psi * 10 cm^3 = 9000 psi cm^3 = P2*2 lt. Now, there are 1000 cm^3 in a litre, and so we have P2 = (9000/2000) psi = 4.5 psi. If you wanted it to be 40psi, then you would need the initial pressure to be 8000 psi, assuming the initial volume is 10 cm^3.

stonemason1

Thanks Professor_Fink for the reply

That is some mind bending maths there

So effectively i need a larger canister, as i think 8000 psi is getting a wee bit dangerous .

Im off to search, but if you know of a reasonable size canister that would do the job please let me know.As mentioned im looking to empty a 2lt bottle of water using a CO2 or any none dangerous gas.

And thanks again

whizbang

it depends on the initial air space in the tank/connections to begin with.
If there is no air space the 900psi is applied directly to the liquid. if 2L of water is displaced then the resulting airspace is 2L at 4.5psi .
If you need initial pressure of 40 psi applied to the tank, that requires an airspace of 900*10 /40 = 225 cc before any liquid is expelled.

ok also this assumed there is no reaction of the water/gas.

stonemason1

Thanks for the input whizbang

What im doing is trying to make a super soaker water pistol run off co2 canisters.I know its not cost affective but i want to get full pressure of 40+psi until the 2lt tank is emptry.:)

thanks again