Water and pressure reduction

[Gabriele]

Hello. I try to explain what i thought.

We take a box contaniner divided in 2 parts by a mobile vertical wall. In one side we put water till a determinated height,to the other side we put a spring to win the pressure applyed to vertical mobile wall. Now we introduce high pressure air to each chamber. The air compress the wall from each side with same force. Als,if we have like 20-30 bar of air pressure,the volume of water reduces by 0,1%. So the density increase but the level of water decrease like the pression on the wall. Is easy to computate. So now the wall will move and expand the spring. Now i let the air exit,the volume of water return the same and so the wall return to original position. Can it work?

[Gabriele]

So.

In Yellow high pressure air

[Low-Q]

Try to do the math if you imaging the water will be compressed 50% at 2 bar pressure.
Using imaginary figures does not change the concept you're looking for. It just might make it easier to calculate.
Also have in mind that air isn't weightless. 1x1x1m of atmospheric air weights about 1.3 kg. 30 bar pressure in a 1000 litre tank is 39kg of air.
Maybe those 0.1% compression of water is accounted for by the weight of air in the spring chamber.


My wild guess is that nothing special will happen to that wall. But it is an interesting thought you brought up. It bugs me a little. I'll look closer into it.


Vidar

[MarkE]

Try to do the math if you imaging the water will be compressed 50% at 2 bar pressure.
Using imaginary figures does not change the concept you're looking for. It just might make it easier to calculate.
Also have in mind that air isn't weightless. 1x1x1m of atmospheric air weights about 1.3 kg. 30 bar pressure in a 1000 litre tank is 39kg of air.
Maybe those 0.1% compression of water is accounted for by the weight of air in the spring chamber.


My wild guess is that nothing special will happen to that wall. But it is an interesting thought you brought up. It bugs me a little. I'll look closer into it.


Vidar

It's just a balance between two pairs of forces.  The minute compressiblity of the water is so somall that for practical purposes it can be ignored.

[MarkE]

So.

In Yellow high pressure air

The wall moves when there is a force difference between the two sides.  One one side is the force that arises from the weight of the water plus air pressure and the other side is force of the spring plus air pressure.  In essence:  two opposing springs find an equilibrium position.