Transactions of the Korean Society of Mechanical Engineers B (대한기계학회논문집B)

The Korean Society of Mechanical Engineers (대한기계학회)
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Evaluation of Critical Flow Function by Using Helmholtz Free Energy for Natural Gas Flow Measurement

천연가스 유량 측정에서 헬름홀츠 자유에너지를 이용한 임계유동함수 계산

  • Ha, Young-Cheol (Gas Quality and Flow Measurement Lab, R&D Division, Korea Gas Corporation) ;
  • Her, Jae-Young (Gas Quality and Flow Measurement Lab, R&D Division, Korea Gas Corporation)
  • 하영철 (한국가스공사 연구개발원) ;
  • 허재영 (한국가스공사 연구개발원)
  • Received : 2013.04.08
  • Accepted : 2013.09.29
  • Published : 2013.12.01
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Abstract

This study aimed to calculate the CFFs (critical flow functions) of a sonic nozzle bank with a 12-nozzle package within 1 s. Toward this end, the Helmholtz free energy of natural gas was formulated by using the AGA8-dc equation of state in a form without integral terms, and thereafter, thermodynamic properties such as the enthalpy, entropy, speed of sound, and heat capacity, which are used in CFF calculation, were derived in analytical form. As a result, the calculation time of CFFs was improved from 6.7 s in a previous study to 0.6 s per 12-nozzle package and kept almost constant regardless of the number of components in natural gas. Furthermore, it was confirmed that the calculated CFF values were in agreement with the results of a CFF international comparison test carried out under ISO management in 1998-1999.

본 연구에서는 천연가스 유량 측정에서 2차 표준으로 사용되는 소닉노즐 뱅크 -12개 노즐 패키지로 구성-의 임계유동함수 계산 시간을 1초 이하로 단축하고자 하였다. 이를 위해 AGA 8-dc 상태방정식을 적용한 헬름홀츠 자유에너지를 유도하고 이로부터 적분 항이 없는 열역학 상태량 식을 도출하여 CFF 계산에 적용하였다. 그 결과 CFF 계산 시간이 기존 6.7초/12개에서 0.6초/12개로 크게 감소하는 것을 확인할 수 있었고 이 계산 시간은 가스 성분 수와 거의 무관함도 알 수 있었다. 또한 본 계산 결과의 정확도를 확인하기 위해 기존 CFF 국제비교연구의 결과와 비교한 결과 차이가 없음도 확인하였다.

Keywords

References

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Cited by

  1. Estimation of Uncertainty in Critical Flow Function for Natural Gas vol.38, pp.7, 2014, https://doi.org/10.3795/KSME-B.2014.38.7.625