Calculating dissolved oxygen content of water given T and P

[pontalpha]

Hi,

I'm just wondering if it's possible to calculate the oxygen content of water given the temperature, pressure and enthalpy. I've tried google but I can only find things like this:

http://www.oroboros.at/fileadmin/user.../2.4.A-O2-Calib-Solubility.pdf

which only deal with low temperatures.

I'm trying to calculate the oxygen content of the feedwater from a deaerator, the only info I have is regular thermodynamic properties like T,P,H, flow rate.

Sorry if this is the wrong forum, wasn't sure of the best place to post.

Thanks.

 

[ione]

You should take a look to Henry’s law and temperature dependence of the Henry constant (not that constant).

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

 

[zdas04]

I've chased this rabbit for years and he is one elusive bunny. All the researchers agree that as you elevate pressure, the Henry's Law "constant" increases, and the magnitude of the increase for a given pressure varies by less than an order of magnitude from researcher to researcher.

Temperature effects are just weird. I have never found two sets of experiments that have similar shapes for the adjustment curves. I have found about the same number of researchers that say the "constant" increases with increasing temperature as say the "constant" decreases with increasing temperature. One PhD candidate suggested that there is a different curve for each bar of pressure change and he provided a few examples that didn't seem related to each other at all.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

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

"It is always a poor idea to ask your Bridge Club for medical advice or a collection of geek engineers for legal advice"

 

[pontalpha]

Ugh, that's not what I wanted to hear! I've been using a formula for the constant I found on wikipedia of all places but I'm getting answers for dissolved oxygen content about 100 times larger than the sort of answers I'm looking for.

Thanks to both of you for the help btw.

 

[rmw]

If you haven't already, Google " Henry's Law ". There are several sites that will pop up that are helpful.

Also, just because you bring water to a T & P, doesn't mean that the air or O2 will come out on its own accord. That is why Deaerators have trays or sprays; to maximize water surface area to the heating and scrubbing steam so that the noncondensables can be liberated.

rmw

 

[zdas04]

I've been chasing this rabbit because many gas gathering companies are starting to get absolutely rabid about the risks associated with dissolved oxygen corrosion in gas lines. I've been an expert witness on this subject and seen the gathering company's "evidence" and it is Wikipedia-level documentation. There is nothing in the primary reference sources that help shed light on this subject and there is a lot of high school math (i.e., "how could there possibly be more than one answer to a given question? Let's just ignore the inconsistencies!") in the literature. There are some serious, honest researchers out there, but their conclusions just add to the chaos so far.

It is amazing to me that dissolved oxygen is the gathering companies biggest issue today, but NACE hasn't has a paper on it in years (as of early 2009, I'm not sure what has been published in the last 18 months). You might look at NACE's e-library for recent papers on the subject.

David