Metering High Pressure Natural Gas- from the National...

Metrology Club Tokyo, Japan14. March 2014

Metering High Pressure Natural Gas-from the National Standard to CFVNs

E. von Lavante, University of Duisburg-Essen

Metrology Club Tokyo 2014

Natural gas as

source of clean energy

But: how much and at what cost?

Metering natural gas: history

1800‘s - W. Murdock, gas utilization

1815 - S. Clegg, 1st dry gas meter

1848 - S. Elster, patent and production

1878 - E. Haas, 1st usefull domestic meter

1936 - Elster Co., 1st turbine flow meter

Introduction


Legal metrology is all about standards and accreditation:

In Germany, accredited test lab according to DIN EN ISO 17025

pigsar

pigsar is national and international standard for high pressure natural

gas with direct traceability to fundamental SI units

May 1999 pigsar and PTB (NMI) jointly hold national standard

June 1999 harmonization with Netherlands NMI VSL

May 2004 further harmonization with French LNE LADG

Sept. 2013 finally, harmonization with Danish FORCE techn.

Eurega

(european reference high pressure gas volume)

National Standard


Eurega


pigsar

Operated by PTB (Physikalisch-technische Bundesanstalt) and

Vier Gas Services (previously e.on previously ruhr-gas)

Integrated in pipeline carying HP NG (~ up to 70 bar)

Primary standard: piston prover, geometric uncertainty 0.007%

traced directly to SI meter

installed mass flow uncertainty U = 0.02

%

Second. standard: turbine flow meter (TFM), 1st stage, U = 0.05 %

Master meter: TFM, up to 8 parallel test lines, U = 0.13 % inst.

(4 x G 1000, 4 x G 250) plus 1 x G 100

or

1 x Instromet DUO RPM (low pulsation)

Transfer standard: TFM U = 0.16 %


pigsar

Summary of installation:(U installed showing older data, now 0.13 %)


pigsar

Traceability chain at pigsar


pigsar

Uncertainties for stages1 - 4a


pigsar

Realization


pigsar

Realization – piston prover


pigsar

Realization – test lines


pigsar

Realization – critical flow Venturi nozzles( U = 0.07 % air, bell prover PTB;

installed HP NG, C ⃰, Mmol , U = 0.12 % )


NMIs


Sonic Nozzles Sonic Nozzles

Aamth

RTcc

av

p

0

*R0

thRT

CAPm

M

zRT

PM


Z-factor

Equation of state - ideal gas, up to approx. 7 bar

Equation of state – real gas, from 7 bar up to approx. 7 Mpa for NG = mixture of real

gases

Determination of the Z-factor: AGA8 DC92 extended by Jaeschke and Schley, up to 30 Mpa and 200 – 1000 K, with 0.1 % accuracy


Z-factor

Derivatian using virial coefficients: from free energy f

In above equation, δ is reduced density and τ reduced temperature


Z-factor


Z-factor


Z-factor

In above equations, K is scale parameter, Kij binary interaction parameter,B the 2nd virial coefficient, Gi and Gj

orientationparameter, Eij binary energy

parameter, Qi quadrupoleparameter and Fi temperature

parameter

Above equations have to be solved by iterative procedure for p, T, and ρ

What is it good for? For example, implementation in NS-code for CFVN


ACHIEVE

Implementation in CFD code ACHIEVE for ISO 9300 CFVN


ACHIEVE

Resulting mass flow as compared to experiment

Eq. of State Num. Method Deviation [ % ]

perfect Navier-Stokes -2.40

ideal Navier-Stokes -2.17

real Navier-Stokes 0.61

Eq. of State Num. Method Deviation [ % ]

perfect Navier-Stokes -3.85

perfect Euler -3.72

ideal Navier-Stokes -3.64

ideal Euler -3.47

real Navier-Stokes 0.19

real Euler 0.54

Pressure 26 bar

Pressure 36 bar


Z-factor

Resulting flow variables along the axis


Z-factor

Resulting flow variables at the throat


Conclusions

Calibration – why?

legal necessity

reference to fundamental units (kg, m, sec.)

liability issues

National standard for LP air of limited value

Need national standard for HP NG with traceability to

[m] and [sec.] if volumetric flow (pipe, piston, bell

prover, optical rig)

[kg] and [sec.] if mass flow (CFVN)

Can a CMC submitted to CCM by accredited lab have lower

uncertainty than a NMI?

Metering High Pressure Natural Gas- from the National...

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