Fixed load being held by a variable volume cylinder - like a hydraulic cylinder?
Fixed temperature but variable volume - as in leaking tank with a gas & liquid inside?
Fixed temperature but losing volume of gas from a constant volume vessel - like an underground pipe with a liquid left inside
Fixed volume but variable temperature and mass of gas inside - like in leaking pipe up in the sunshine?
COME ON! Be a professional and describe YOUR problem!
You still need much more information before you can start to calculate this.
In short
Is there any air input into your vessel during this leaking period? If so how much?
What is the start pressure and temperature of your tank?
Most importantly - What is the internal volume of your tank / vessel??
without that basic data you have no chance of calculating the impact of a leak in terms of internal pressure drop over time.
In any event, the effect of the volume leak will change over time as the amount of air decreases.
Remember to do all your calcs once you get this info in absolute pressure and temperature
Is your leak volume rate at atmospheric conditions?
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
do you have a static pressure vessel or a dynamic pipe flow problem ?
1) if you have a static pressure vessel, PV=constant will help you. if you know your initial pressure then you're GTG, since someone has told you n, R, T [is it just me or does this sound like a student problem ? in practice, would you know nRT or PV ?]
guessing that your volume leakage is measured at atmospheric conditions, then you know how much "stuff", the "n", is leaving the pressure vessel, then you can calculate the pressure drop.
2) if it's a pipe problem, then you're looking for the pressure drop across the leak. and you need more info (pipe static pressure, flow rate) ... so it sounds like it's 1) ...
another day in paradise, or is paradise one day closer ?
bonll,
What the responders are trying to help you with is also known as the "perfect gas law".
Wikipedia has a page that may provide more insight into your problem, and how these folks are trying to help.
How were you able to determine the leak rate at 0.0027 cu. in./sec, another word tell us the scope of the project in which you determine that leak rate.
not homework really,
have a pressure loss of .008 psi on a leak tester was told that it equated to 0.0027 cubic inch p/second but I need to prove this.
The people who originally set this up are no longer here and the Leak test company no longer in biz.
leak tester (provides external pressure on a unit) testing a unit for leaks, the machine will fail a unit with a loss of .008 psi.
what about PL at .008 psi?
Calculated knowns...
L.R. = PL V / t
n = 0.011548824 (at 68 deg F)
PL = .008 psi
V = 178.2
atm 14.7+8.6 = 23.3
t = 8 secs
Pa Test = 157953.7673
R = 8.134
T = 293.15 K
Now we're getting somewhere - why did you not give us all this info at the start??
Questions -
why is atm 14.7 PLUS 8.6?? where are you doing this? what does the +8.6 represent? I've seen lower than sea level atm pressure at higher altitudes but not higher unless you're in a dive chamber?
Volume is 172.2 cubic inches?
Pa test - is this in absolute units of Pascals or what?
Also I would love to know how what you use to measure 0.008 psi pressure drop over 8 seconds with any repeatability or accuracy. This sounds like serious lab type equipment.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
a chamber (alum box, with a unit in it) is filled with 8.6 psi for testing a unit (so 1 atm + 8.6), V in cc.
Pa absolute Pascal.
machine is fairly repeatable, again this was handed down to me.
you know n,R,T and P (pressure = 8.6psi) so you can calc V and compare with known to validate other parameters.
btw ... use consistent units !! we're mixing all sorts.
how do you know the volume leakage rate ? i mean you're not collecting the leakage in a balloon and measuring it ??
but you can calculate the amount of "stuff" (air) from pv = (n1)*Rt ... p = 1 atm, v = leakage, t room temp? >>> calc n1
then back to the testing tank to calc p (due to leakage) = (n1)*RT/V
... no?
another day in paradise, or is paradise one day closer ?
I did this just for a laugh and for a leakage rate of your .0027 in^3 equates to .0035 psi.
Now I could have got that wrong, but it's a benchmark to work from. I worked tat on the basis that your leakage rate was measured at atmospheric conditions not the pressurised one and we're talking such small numbers any error on a big number means an error on the much smaller one.
I would love to know what this is for though...
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
we're using such hyper-precise numbers as Pa Test = 157953.7673, but 8.6psig = 1.585atm = 160603.6Pa
157953.7673 (sic) Pa = 1.559atm = 22.9psi = 8.2psig
(i'm using 1atm = 101325Pa)
with data provided PV = 28.15 (with the correct R = 8.314; i'm guessing the units match)
(how the heck do you know "n" ?)
with P = 56629, V = 0.000497m3 = 497cc ... not your 178cc ... must be doing something wrong, haven't done this type of chem in 30+ years
with your PV = 56629*0.000178 = 10.1 ... no?
n = 10.1/(293*8.314) = 0.004146 ?
another day in paradise, or is paradise one day closer ?
