solubility effect of air in seawater in ballast system of sub

[mmcgeogh]

I am trying to determine what the precharge should be in a ballast tank to allow for resurfacing after some of the air has gone into solution in the seawater due to the high pressures at 20,000 ft below the surface ~9,000 psi, and is pumped out with the water during the ascent. Any help would be appreciated.

 

[GregLocock]

Don't know exactly, but you are looking for data like this:

http://www.engineeringtoolbox.com/oxygen-solubility-water-d_841.html

and

http://www.engineeringtoolbox.com/air-solubility-water-d_639.html

It would take a while to reach equilibrium.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[zeusfaber]

If you're relying on a precharge to enable you to pump all the water out a ballast tank, aren't you going to have to work unnecessarily hard to pump the water in in the first place?

I'm sure this is why the normal plan (at least for big black boats) is to:

1. Use hydrodynamic controls to get you somewhere near the surface.

2. Take a separate supply of HP air with you to displace enough water to get you positively buoyant while still completely immersed

3. Rely on an LP blower to push out the remaining ballast with ambient air to increase your freeboard once you've broken surface.

If the HP air lives in a cylinder during the deep-dive phase, you're less like to see problems with it dissolving in the ballast.

A.