11th February 2008 - 09:55 PM
I really don't know anything about this but exactly how much does air compress? 90 psi is 6x atmosphere right? But that doesn't mean 6 cf of air becomes 1cf at 90 psi like i just read on another site does it?
I guess what I am getting at is alot of compressed air in the world. All the tires from 30-100 psi, air compressors and tanks. And now theres talk of wind turbines compressing air and storing it instead of using electric lines. Does all of this compressed air have enough effect to decrease atmospheric pressure any at all?
Its no big deal really I have just always wondered.
11th February 2008 - 10:26 PM
If 6 cf becomes 1 cf under pressure, how much do you think that would affect the pressure gradient in the atmosphere between sea level and, say, 100 mi, since we're working with English units?
How many cf of air do we have, roughly?
11th February 2008 - 11:23 PM
Yes, multiplying the pressure by a factor of 6 reduces the volume by a factor of 6. Provided that the temperature remains the same, which usually isn't true when you compress a gas, so you will need to cool it back before observing the volume.
Another difference appears when the density of the gas becomes similar to that of the liquid, in which case the gas is less compressible. More accurate equations take it in account: Have a look at "virial coefficients" for instance, or at "van der Waals". This is already the case with air or nitrogen at 300 bar, which is a technologically usual pressure.
12th February 2008 - 12:02 AM
Welcome. I think this is really your question.
>Does all of this compressed air have enough effect to decrease atmospheric pressure any at all?
Short answer is Not at all. All compressed air storage is temporary, it will be released back after some time.
12th February 2008 - 02:07 AM
I know it wouldn't permanently have an effect but there is a lot of compressed air at any given time. I have worked at factories that have multiple 60,000 gallon tanks used for compressed air with miles of 12" airlines at 300 psi. And it is always being used not to mention the millions of tires there are.
So anyone know how many cubic feet of air we do have? That would be a tough one to figure up but you say 100 miles? yet there is very little air at 10 miles. hmmm might have to do some calculations...
Anyway I was just reading where this guy wanted to makes wind turbines compress air so it could store it and even bury airlines allover at 10k psi... that would add up to a lot of cf.
12th February 2008 - 02:30 AM
>I know it wouldn't permanently have an effect but there is a lot of compressed air at any given time. I have worked at factories that have multiple 60,000 gallon tanks used for compressed air with miles of 12" airlines at 300 psi. And it is always being used ....
The key word here is "USED" An air compressor only turns on if the pressure drops and it will only drop if it is being sent back into atmosphere. It's just in one end and out the other. how long it stays sequestered really doesn't matter that much.
12th February 2008 - 03:04 AM
So your saying a 60k gal tank x .16 = 9600 cf x 300psi = 2,880,000 cubic feet of air to fill this one tank? Then 2 tanks + a couple miles of 12" pipe = 7,310,000 cubic feet of air. I know I didnt take into account atmosphere pressure of 14.97psi but its all close. Right?
Ok well then you have what 250,000,000 vehicles in the US and lets say average 3cf of air per vehicle x average 50 psi = 150cf x 250,000,000 = 37,500,000,000. Well I guess thats not bad considering there is close to 150 billion cf in one cubic mile.
but this guy is talking tanks at 10k psi so 1 10,000cf tank x 10,000psi = 100,000,000 and then thousands of miles of pipe at 10k psi? hmm 2000 miles would be somewhere around 633,600,000,000 cf. that alone is 17 cubis miles of air.... You dont think that would have a slight effect?
12th February 2008 - 03:08 AM
The factory is always in operation therefore theres always 7 million cubic feet of air in the tanks and lines. I know its comeing and going but theres always that amount in there no matter what. That means that 7 million cubic feet of air is not exactly in the atmosphere... and most people keep their tires aired up at all times too =P
12th February 2008 - 03:39 AM
I am going to guess 600 million cubic miles of air at 15 psi on earth? A few cubic miles wont hurt much but has to make a tiny difference