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소닉노즐을 이용한 천연가스 유량측정에서 임계유동인자 계산
Evaluation of Critical flow Factor in Natural Gas Flow Measurement Using Sonic Nozzle
HWAHAK KONGHAK, August 1999, 37(4), 582-586(5), NONE
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Abstract
소닉노즐은 가스유량계 교정에 널리 사용되는 기준기이다. 소닉노즐로 흐르는 유량을 계산하기 위해서는 임계유동인자라는 노즐 목 조건의 열역학적 물성값이 필요하며 ISO-9300은 이에 대한 계산방법을 제공한다. 그런데 이 방법으로 계산한 임계유동인자는 특정 조건에서 0.5% 이상의 오차가 발생할 수 있고 일반적인 천연가스 거래조건에서도 0.1% 이상의 오차가 있음이 보고되어 있어서, 높은 정확도가 요구되는 천연가스 유량측정에 적용하기는 어렵다. 따라서 본 연구에서는 ISO의 방법보다 정확하게 임계유동인자를 계산하고자 하였다. 이를 위해 현재까지 가장 정확하다고 알려진 천연가스 상태방정식 AGA-8(''94)을 이용하였고, 이상기체의 물성계산 모델도 불확도 ±0.05% 이내의 계산식을 사용하였다. 그 결과 본 연구에서 계산한 임계유동인자는 천연가스 거래조건에서 ±0.1% 이내의 정확도를 보여준다.
Sonic nozzle is widely used for reference of calibrating flowmeters in gas flow measurement and its use requires the critical flow factor on the thermodynamic properties of the gas at the nozzle throat. ISO-9300 provides the calculating method of the factor. But since the critical flow factors from this method show an errors over 0.5% in specific conditions and over 0.1% in general NG custody transfer condition, this method cannot be applied for gas flow measurement with sonic nozzle. Therefore in this study, the other method is used to calculated the critical flow factor for higher accuracy than the ISO method. The equation of state from AGA-8(''94) and high accuracy(within±0.05) model of ideal gas properties are used in calculating the factor. The results of this study show that the accuracy of critical flow factors are within ±0.1% in the NG custody transfer condition.
Keywords
References
ISO 9300, International Organization for Standardization, Geneva (1990)
Johnson RC, NASA Report SP-3074 (1972)
AGA Report No. 8, American Gas Association (1994)
Passut CA, Danner RP, Ind. Eng. Chem. Process Des. Dev., 11, 543 (1972)
Aly FA, Lee LL, Fluid Phase Equilib., 6, 169 (1981)
McFall RL, Master Thesis, Unversity of Oklahoma, Oklahoma, U.S.A. (1984)
Sivaraman A, Bammon BE, NIPPER Report 142 (1982)
Gammon BE, Sivaraman A, Gas Research Institute, Final Report, GRI-86/00043 (1986)
AGA Report No. 9, American Gas Association (1998)
Stewart DG, "Improved Critical Flow Factors and Representative Equations for Four Calibration Gases," Proceedings of FLOMECO'98 (1998)
Johnson RC, NASA Report SP-3074 (1972)
AGA Report No. 8, American Gas Association (1994)
Passut CA, Danner RP, Ind. Eng. Chem. Process Des. Dev., 11, 543 (1972)
Aly FA, Lee LL, Fluid Phase Equilib., 6, 169 (1981)
McFall RL, Master Thesis, Unversity of Oklahoma, Oklahoma, U.S.A. (1984)
Sivaraman A, Bammon BE, NIPPER Report 142 (1982)
Gammon BE, Sivaraman A, Gas Research Institute, Final Report, GRI-86/00043 (1986)
AGA Report No. 9, American Gas Association (1998)
Stewart DG, "Improved Critical Flow Factors and Representative Equations for Four Calibration Gases," Proceedings of FLOMECO'98 (1998)
