A hose inside a pressurized pipe...

[Externet]

Hi all.

 

If a lenght of empty (with atmospheric air) aquarium hose is plugged with beads of silicone sealant at the ends; and placed inside a plain household water pipe...

 

When the water pipe is placed in operation, at say 3 Atm water pressure, the hose inside will contract/deform due to the pressure.

Would the plugs at the ends tend to burst outwards or inwards or will not be affected at all ?

 

Just want to confirm am not missing something here...

 

Miguel

[Rocket Man]

the silicone probably won't move under 3bar, but if they move, they'll move into the pipe unless the pipe itself deforms.

considering the rigidity of aquarium tubing, the pipe won't get crushed. the silicone probably won't go anywhere either.

supposing the pipe deforms to match outside pressure, the silicone won't go anywhere (zero net force).

[Externet]

the silicone probably won't move under 3bar, ........).

 

Thanks.

Why do you say "probably" ?

 

Do you imply that if the water pressure is 100 Atm instead of 3 Atm the behavior would be different?

 

Miguel

[John Cuthber]

If you assume that the aquarium pipe is pretty soft then the end plugs won't move in or out.

The water pressure will squash the pipe until the pressure in it is 3 bar. There will then be the same pressure inside the pipe as outside it so there's no net force on the plugs.

If you used a stiff metal pipe or very flexible plugs then the plugs would move in.

If you used stiff plugs then the pipe would deform and they would stay put.

[Rocket Man]

i say probably because you can seal up the end of a hose pipe with silicone.

and yes, if the pressure were 100bar, the behaviour would be quite different.

the compressible fluid in the pipe will attempt to occupy 1/100th of it's initial volume. such an attempt action is likely to rip the pipe around the silicone whilst pretty well inverting the tube. air is heavy. 100x air is very heavy.

[John Cuthber]

What exactly do you mean by "air is heavy. 100x air is very heavy".

Even at 100 bar air is less dense than water.

[doG]

The pressure in the pipe will increase the pressure in the hose. The pressure in the hose will act in all directions equally. The pressure in the hose will not increase to the pressure outside the hose unless it is filled with fluid since air itself is compressible therefore the pressure in the pipe would tend to push the plugs into the hose with a hose full of air. Google Pascal and Boyle.

[Rocket Man]

air isn't very dense, but consider the pressure head of air above us.

pulling a vacuum is displacing a 100km tall column of air. that's a lot.

100bar is one hell of an energy density if there's a compressible fluid. things get explosive quickly. 100bar puts almost 120 kilos on every square centimetre of exposed surface area.