Finding out compressibility of a fluid when bubbles are present?

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Discussion Overview

The discussion centers around the compressibility of a fluid when gas bubbles, specifically H2O, are present. Participants explore the theoretical and practical aspects of calculating the compressibility of a liquid-gas mixture, particularly in the context of flow calculations and experimental methods.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the compressibility of a fluid with H2O bubbles and seeks methods for calculation.
  • Another participant requests clarification on what is meant by "H2O bubbles," indicating a potential misunderstanding of the state of water at different temperatures.
  • A participant suggests that if a liquid with known compressibility has gas bubbles added, the mixture's compressibility could potentially be calculated by summing the compressibilities of the liquid and gas, factoring in their mass fractions.
  • It is noted that H2O does not form gaseous bubbles unless above its boiling point, leading to a suggestion that other gas bubbles might be considered instead.
  • One participant argues that there are no established look-up tables for the compressibility of liquid-gas mixtures and suggests that experimental measurement may be necessary.
  • A participant expresses interest in flow calculations involving a liquid that is essentially incompressible and seeks a rough estimate of the mixture's compressibility.
  • Another participant references a patent related to measuring non-dissolved gas in liquids, suggesting that there may be existing work in this area.

Areas of Agreement / Disagreement

Participants do not reach a consensus on how to calculate the compressibility of the liquid-gas mixture, with multiple competing views on the feasibility of theoretical calculations versus the necessity of experimental measurement.

Contextual Notes

Participants express uncertainty regarding the conditions under which H2O bubbles can exist and the applicability of existing methods or tables for measuring compressibility in mixtures.

bzz77
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I want to know approximately how compressible a fluid can become when H2O bubbles are present. Does anyone know how to do this? Thanks.
 
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bzz77 said:
I want to know approximately how compressible a fluid can become when H2O bubbles are present. Does anyone know how to do this? Thanks.

Will you please explain what are "H2O bubbles"? Thank you.

Bobbywhy
 
Thanks for your response, Bobby.

I mean that if we have liquid and know its compressibility (it is approximately incompressible), then we add some gas bubbles to it (of known composition, let's assume H2O), then how can we calculate the mixture compressibility?

Is this a matter of looking up tabulated values for the gas compressibility at the temperature and pressure of interest, then summing the liquid and gas compressibilities, taking their mass fractions into account?
 
H2O (water) does not form gaseous bubbles unless raised above its boiling point. Are you thinking of some other gas bubbles in water?

Compressibility is the fractional change in volume per unit increase in pressure. It seems reasonable to expect that if gas bubbles are added, then the volume would decrease more under the same pressure because gas is far more compressible.

There are not “look-up tables” for such mixtures. I think your only option would be to perform the experiment and measure the compressibility of the mixture.

Bobbywhy
 
Thanks, Bobby. I'm thinking of a liquid that is not water, but that is essentially incompressible. it would be at temperatures high enough that water gas would be stable. I want to do some flow calculations and I'd like to get a rough idea of how compressible the liquid plus gas mixture would be compared to liquid only.

I was hoping there might be a rough way to calculate this, but it appears not. Anyway, thanks a lot.
 
bzz77, There may be work already done in the area you are interested in. See this patent, for instance:

"Method and apparatus for the determination of non-dissolved gas in liquids
ABSTRACT
The method enabling the quick determination of non-dissolved or free gas in a liquid sample. Involves measuring the density of a liquid sample in a closed vessel, subjecting this sample to a reduced pressure and thereby expanding the "free" gas in the liquid sample. After this expansion has taken place, but before allowing dissolved gas to come out of solution, the volume is fixed and a second density measurement is taken."
http://www.google.com/patents/US4584866

Bobbywhy
 
Thanks a lot, Bobby. I expected that this would be something done routinely, so it is interesting to know that it isn't.
 

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