1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Theoretical pressure chamber

  1. Apr 23, 2013 #1
    Now I am just thinking about pressures and material strengths and I came across a question.To formulate the question I am going to explain a little bit of a thought situation.

    Normally if you would have a let's say sphere with very thick walls and you would increase pressure of a gas inside the sphere the pressure on the walls would bet higher and higher until the walls would give way and come apart.
    Now let's imagine a sphere in another sphere with sphere 1 is 1/2 as sphere 2.For the sake of argument let's assume that sphere 2 walls are of a infinitely strong material but sphere 1 that is inside sphere 2 is with normal metal walls of a given thickness etc.
    Now if sphere 2 can hold any pressure then putting higher and higher pressure in sphere 1 and putting the same amount of ever increasing pressure between sphere 1 and 2 would result in no failure ?
    As I understand if you have equal pressures from both sides of a wall or sphere or any physical object or construction then the object should hold even with huge pressures , ones that the object could never hold if the pressure would be just from one side?

    So for example if I have alot of spheres each next one bigger than the last and some free space between them , then if all of them would be made form the same metal with the same thickness the outer ones would have less pressure inside them but going smaller to the inner ones each next one could have higher pressure inside it because it would be smaller and thus the same material could hold bigger amounts of pressure in right ?
     
  2. jcsd
  3. Apr 23, 2013 #2
    I think this makes sense. You're essentially asking if a higher pressure can be reached by placing one pressure chamber inside another? Because the mechanical failure occurs when the pressure difference across a component exceeds some critical limit, putting two of those components in series (one inside the other) increases the total pressure difference that can be achieved?

    I can't find a problem, in theory.

    My question would be, how do you build this? Once you have built this arrangement at atmospheric pressure, how can you add molecules to the innermost sphere without compromising the outer ones?
     
  4. Apr 23, 2013 #3
    Well perfectly if I would have like two spheres and the outer bigger one would have some kind of "magical" walls that can bear nay pressure added to them then the inner sphere could be of almoust anything as the pressure could be put the same both in the inner sphere and between the inner and outer.you could put identical pressure from both sides hence making the sphere wall material very thin as it would not have to bear any stress.
    This ofcourse is a unreal situation so here is the more to life version.

    let's assume I want to get something in the order of 50 million atmospheres of pressure , normally if I would want to get this in a single sphere, there I guess is no material know to man yet that could hold such a pressure due to the extreme forces the outer walls of a container would have to bear.
    Now but I never said how much volume of gas I need at these 50 million atmospheres just need the pressure so Could I go with having let's say 10 spheres (in real life they would probably need to be alot more ) Now the first sphere the outermost one also the biggest is let's say 10m in diameter and has very thick strong metal walls now the next one sits inside the first one with a diameter of 9m between these two is a space filled with gas at a given pressure.Now every next sphere would be smaller and also with higher pressure and could have thinner walls because the walls would not have to support the ever increasing pressure alone they would be backed up by the slightly lower pressure from the previous space between the previous spheres.
    As I believe a given materials strength or the ability to resist pressure or force gets bigger with decreasing surface area.

    As to how to feed the gas inside each of the spaces between the spheres , well I guess very small but strong pipes , they would be strong because again they would be extremely small also the flow then could be small but at these pressures I think you can move a significant amount of gas or fluid even through a small pipe.

    Well what do you think how much reality is in this theoretical idea?Just wondering?
     
  5. Apr 23, 2013 #4

    AlephZero

    User Avatar
    Science Advisor
    Homework Helper

    Your basic idea is correct. In fact this idea has been used for hundreds of years, to allow gun barrels to withstand high pressures. Originally, that was done by deliberately firing a "proof charge" which was high enough to permanently stretch the metal in the barrel and leave a compressive stress in the material, which had the same effect as applying pressure to the outside of the barrel from then on.

    Howver you can't continue this "for ever" with multiple spheres, because the inside sphere has to resist the compression of the two high pressures on either side, and a high enough pressure will crush the material. But the crushing strength is usually a lot higher than the tension (stretching) that the material can survive without failing.
     
  6. Apr 24, 2013 #5
    Well forever was meant just theoretically , in real life it could be any given number take let's say 5 spheres as you can see in my attached picture that I made up.
    yes because crushing a sphere would be harder than to stretch it from inside and explode it like a balloon.
    Now but the smaller spheres would have higher pressure in them but the outer walls of each smaller sphere would be pushed against from the pressure that surrounds it even though smaller.

    Now the idea is that you start with say sphere 5 which has a let's say 100A of pressure now sphere 4 has 120 for example it can hold more atmospheres in itself because it is smaller even though from the same material +it is being supported from the outside with a smaller but backpressure.
    Now the idea is that as you go to each next smaller sphere the pressure in it would be greater.
    Now I have a question what would happen with the outermost largest sphere , even though big, would it feel each pressure of each sphere added together ? Or to say this more clearly isn't the pressures even though separated by a sphere wall adding up a total pressure which is felt by the last wall of the biggest sphere , considering that after that there is normal; air atmospheric pressure but in the spheres there is a pressure that is alot higher than atmospheric?


    Oh and another question , assume we have a single sphere with a pressure in it , created by a pressurized gas in the sphere , now assume there is a pipe going right though the sphere , if the pipe is sealed from atmospheric pressure and not crushed by the pressure in the sphere would then any liquid or gas in that pipe be affected by the spherical pressure exerted on the walls of the pipe? I guess no but confirmation would be great.
     

    Attached Files:

  7. Apr 25, 2013 #6
    Excuse me for bumping I just am afraid this might get forgotten. :)
     
  8. Apr 26, 2013 #7
    The atmosphere of the earth, or that of any planet, models your enclosed spheres. Pressure increases in an inverse relationship to the radius. You could put some thin spheres of material enclosing the earth at successive increasing distance from the centre and you have something similar to your system.

    The earth atmosphere cpould be considered the infinite system of shells whereby the pressure on the interior surface of a shell equals the pressure on the exterior surface of the shell, whereas in your system there is a definite disrete jump of pressure from one enclosed space to another. The material shell is what maintains the pressure difference by the stress induced upon the shell from the pressure differential.

    You may take note that the greater pressure in the innermost shell does not transfer to the outermost shell.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Theoretical pressure chamber
  1. Compressed chamber (Replies: 5)

  2. Vacuum chamber (Replies: 4)

  3. Cloud chamber? (Replies: 2)

Loading...