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Flow Meter Temperature And Pressure Compensation Factors


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#1 sgkim

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Posted 06 April 2017 - 05:34 AM

Hi Cheresources Members, 

 

For the differential pressure type flow meter the mass flow of liquid or gas can be calculated as follows (Ref: ISO 5167-2003 in Metric Unit).  Is there any "generalized or model-specific temperature and pressure compensation factor" to convert measured point flow to actual (or real) flow ?   

 

Qm = 3.512407(10^-5)* C * (1-β^4)^-2 * ε * X * d^2 * Fs * (DP * ρ)^0.5 .................(1)

 

      Qm=Mass Flow, [kg/s]   

      C = Orifice Discharge Coefficient = func of (D, β, ReD), [-]

      β = Orifice Diameter to Pipe Diameter Ratio = d/ D, [-]

      d, D = Diameter of Orifice, Pipe, respectively, [mm]

      ε = Expansion Factor = func of (β, DP/p Ratio, κ(=Cp/Cv)),  Cp, Cv=Isobaric, Isochoric Specific Enthalpies respectively

      X=Flow Meter Reading Scale as 0~10,[-]

      Fs=Steam Quality Correction Factor = 1 + 0.0074 w  , w= Liquid Content in Steam, [w%], Fx=1 for Liquid or Gas

      DP=Differential Pressure, [Pa], p = Absolute Inlet Pressure,[bar] 

 

Any guidance would be helpful for me, thanx in advance.

 

~Stefano

 

 

 



#2 shvet

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Posted 07 April 2017 - 10:29 PM

Please define more exactly what do you need.

If you have mass flowrate (eq. 1 ISO 5167-1:2003) it can be converted to actual volumetric flowrate with equation (2):

 

Qv=Qm/p

where p - is the fluid density at the temperature and pressure for which the volume is stated


Edited by shvet, 07 April 2017 - 10:29 PM.


#3 sgkim

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Posted 12 April 2017 - 05:18 AM

Hi Shvet,

 

If the flow rate is measured at exactly the same "reference temperature and pressure Tr and Pr", then the measured flow, Qr, may not be compensated.  But if the flow is measured as Qm, at measuring temperature and pressure, Tm and Pm, then the measured flow shall be compensated with respect to corresponding temperature and pressure.

 

Qr = f(Tr, Pr),    Qm = f(Tm, Pm) =measured value but not accurate.

 

So the compensation factor(CF) would be employed as  

 

CF ≡  Qr/Qm = f(Tr, Pr)/f(Tm,Pm); then   (Qr) = CF* (Qm),

 

How CF could be implemented as a general function of Tr, Pr, Tm, and Pm ?    In eq(1),  d, D, β, Re, ε, DP, ρ, and μ in Re are subject to be changed with respect to the change of temperature and pressure. 

 

CF = function of (d, D, β, Re, ε, DP, ρ, and μ),  or  simply 

     = func of (Tm, Pm)  ??            ..............(3)   

 

There would be a generalized equation for the CF given in eq(3), which is my understanding. 

 

Thanks in advance,

 

Stefano


Edited by sgkim, 12 April 2017 - 11:26 PM.


#4 ieseberri

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Posted 27 May 2017 - 03:29 PM

Hello,

 

I write a blog entry some months ago about this subject, you can read it here :

 

http://instrumentati...sation-formula/



#5 sgkim

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Posted 30 May 2017 - 08:47 PM

Hi Ieserri, 

 

Thank you for your response introducing a web site which helps somewhat.  But, what I have been looking for was a general, or practical equation that would interpret more precisely the influence of measuring condition on the true flow rate.   Temperature, for instance, would give effects on the density, viscosity, and also on the size of the orifice, etc. So the measured flow rate, I understand, should be compensated considering the combined effect of the temperature.  

 

Thanks a lot..   ~Stefano



#6 breizh

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Posted 30 May 2017 - 09:36 PM

Hi Stefano ,

 

http://www.documenta...d301224x012.pdf

 

You may find pointers using this link.

Hope this is helping you.

Breizh



#7 sgkim

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Posted 02 June 2017 - 03:25 AM

Tanks a lot Breizh,  

 

As introduced, these materials helps quite a lot:  AGA Report 1992//GPA 8185-92//ANSI/API 2530

~Stefano






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