Pressure change during cooling in 20m deep water

[jscippo]

I'm trying to describe the way that pressure changes after I heat a controlled volume of air (assume hermetically sealed box) from RT to 47C and then quench in 10C water that is pressurized to 30psi.

 

[Zoobie]

What does the pressure of the water have to do with the problem? If I read what you say correctly than you are taking a box of air from room temperature and heating it to 47C and then cooling it to 10C. Are you interested in just the pressure at these states or are you also interested in rate of change?

If you are simply interested in the pressure in the box and not how fast it gets there, then it is irrelevant as to what surrounds it as long as the heat sink is large enough. For example if you dumped your box into a lake at 10C than after a period of time the contents of the box would be at 10C and all you need to do is solve (P1/T1=P2/T2)...assuming you have a rigid sealed box...ie no volume change. If you put the box into a bucket of water than you probably need to worry about getting a different equilibrium temperature.

I don't see how the depth of water effects anything in this case (but perhaps I am assuming too much). If you are looking at a heat transfer problem (as opposed to the steady-state thermodynamic state of your control volume) than what your water quench looks like and does makes a difference. However, the depth of it will make little difference at all. 30 psi will not change the physical properties of water by any significant amount (things like heat capacity and thermal conductivity).

I hope I haven't assume too much. If you could fill in the blanks a little then perhaps we can get to your ultimate answer...it doesn't look like a very difficult problem.

 

[MintJulep]

Furthermore, if you are only concerned with the end states, and not the transient characteristics, the quench media has nothing to do with the problem.

Pressure will change the density of the water, which in turn will alter the conduction coefficient to some degree. I'm not sufficiently interested to figure out how much.