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Old   July 7, 2003, 00:05
Default Convert to concentrarion?
  #1
Joly
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I use multiphase to simulate the flow in the pipe line to mixed water with te air. The result is the volume fraction and i want to use the concentration

Any one know, How can i change to the concentration?

Thank you

Joly
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Old   July 9, 2003, 07:58
Default Re: Convert to concentrarion?
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cfd guy
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It is always a question of which units you desire for your concentration. Is it mass / volume? Concentration is a generic word and actually even volume fraction is a kind of concentration [e.g. for 2 phases: VolPhase1 / (VolPhase1 + VolPhase2)].
In terms of mass / volume should be: Conc1 = VolFrac1 * AverageRHO [Kg / m3 in SI]
where AverageRHO is the density average, e.g.: AverageRHO = (RHO1 + RHO2) / 2
or
AverageRHO = Sqrt(RHO1 * RHO2)
Of course that might be hundreds of different averages procedures. Hence, it is up to you to choose the one you want.

Regards, cfd guy
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Old   July 10, 2003, 08:04
Default Re: Convert to concentrarion?
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Nyatoto
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Hi Joly, I think i do not understand the concept you are talking about or your question is not well posed!!

When you study a multiphase system, one of the parameters of importance is phase hold up, which is volume fraction in simpler terms. If you talk about concentration you must specify the units you want, as cfdguy has rightly put.

Cocentrations are typically given (in any units of ones choice) with respect to a given species. In your case you have water and air as your species. Let us begin from here. Which concentration are you looking for?? I am sure you know that if it is air then you need to apply some gas laws that relate volume,moles,pressure, temperature etc.

Nyatoto
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Old   July 10, 2003, 15:00
Default Re: Convert to concentrarion?
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Joly
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Thank you cfdguy and Nyatoto for your recommendation.

I want to know the oxygen concentration came from the air.Can i calculate it and how?

Thank you Joly
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