Korean Chemical Engineering Research

The Korean Institute of Chemical Engineers (한국화학공학회)
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Flow Regime Transition in Air-Molten Carbonate Salt Two-Phase Flow System

공기-탄산용융염 이상흐름계에서의 흐름영역전이

  • Cho, Yung-Zun (Nuclear Fuel Cycle R&D Group, Korea Atomic Energy Research Institute) ;
  • Yang, Hee-Chul (Nuclear Fuel Cycle R&D Group, Korea Atomic Energy Research Institute) ;
  • Eun, Hee-Chul (Nuclear Fuel Cycle R&D Group, Korea Atomic Energy Research Institute) ;
  • Kang, Yong (Department of Chemical Engineering, Chungnam National University)
  • 조용준 (한국원자력연구원 핵주기공정기술개발부) ;
  • 양희철 (한국원자력연구원 핵주기공정기술개발부) ;
  • 은희철 (한국원자력연구원 핵주기공정기술개발부) ;
  • 강용 (충남대학교 화학공학과)
  • Received : 2009.05.07
  • Accepted : 2009.06.22
  • Published : 2009.08.31
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Abstract

In this of study, effects of input air velocity(0.05~0.22 m/sec) and molten carbonate salt temperature ($870{\sim}970^{\circ}C$) on flow regime transition have been studied by adopting a drift-flux model of air holdup and a stochastic analysis of differential pressure fluctuations in an air-molten sodium carbonate salt two-phase system(molten salt oxidation process). Air holdup where the flow regime transition begins was determined by air holdup-drift flux plot. The air holdup value which the flow regime transition begins was increased with increasing molten carbonate salt temperature due to the decrease of viscosity and surface tension of molten carbonate salt. To characterize the flow regime transition more quantitatively, differential pressure fluctuation signals have been analyzed by adopting the stochastic method such as phase space portraits and Kolmogorov entropy, The Kolmogorov entropy decreased with an increasing of molten carbonate salt temperature but increased gradually with an increase in an air velocity, however, it exhibited different tendency with the flow regime and the air velocity value which flow regime transition begins was same to the results of drift-flux analysis.

본 연구에서는 기체(공기)-액체(용융탄산염) 이상 흐름계(용융염산화 공정)에서 공기유속(0.05~0.22 m/sec) 및 탄산용융염의 온도($870{\sim}970^{\circ}C$)가 흐름영역 전이특성에 미치는 영향을 공기 체류량의 drift-flux 및 차압요동의 추계학적 해석을 통하여 규명하였다. 흐름영역이 시작되는 공기 체류량값은 공기체류량-drift flux 그래프를 통하여 구하였다. 흐름영역 전이가 시작되는 공기 체류량 값은 탄산용융염의 온도가 증가함에 따라서 증가하였는데 이는 탄산용융염의 온도가 증가함에 따라서 액상의 점도와 표면장력의 감소로 인한 계의 안정화 때문이며 계의 특성에 가장 큰 영향을 미치는 기포특성(평균기포크기 및 상승속도)을 drift-flux 모델식을 적용하여 추정하였다. 흐름영역전이 특성을 좀 더 정량적으로 특성화하기 위하여 차압요동신호를 상공간투영 및 Kolmogorov entropy를 이용하여 해석하였다. Kolmogorov entropy는 탄산용융염의 온도가 증가함에 따라 감소하였으며 공기유속이 증가함에 따라서 증가하였으나 흐름영역에 따라서 다른 경향성을 나타내었고 흐름영역이 시작되는 공기유속값은 공기체류량의 drift-flux 해석으로 유도된 결과와 동일하였다.

Keywords

Acknowledgement

Supported by : 교육과학기술부

References

  1. Kang, Y., Woo, K. J., Cho, Y. J., Song, P. S., Ko, H. H. and Kim, S. D., 'Search for the Intrinsic Order of Gas-Liquid Flow in a Bubble Column,' HWAHAK KONGHAK, 35, 649-654(1997)
  2. Kang, Y., Cho, Y. J., Woo, K. J., Kim, K. I. and Kim, S. D., "Bubble Properties and Pressure Fluctuations in Pressurized Bubble Column," Chem. Eng. Sci., 55, 411-419(2000) https://doi.org/10.1016/S0009-2509(99)00336-X
  3. Hsu, P. C., Foster, K. G., Ford, T. D., Wallman, P. H., Watkins, B. E., Pruneda, C. O. and Adamson, M. G., "Treatment of Solid Wastes with Molten Salt Oxidation," Waste Manage., 20, 363-368(2000) https://doi.org/10.1016/S0956-053X(99)00338-4
  4. Kang, Y., Lee, K. I., Shin, I. S., Son, S. M., Kim, S. D. and Jung, H., 'Characteristics of Hydrodynamics, Heat Transfer and Mass ransfer in Three-Phase Inverse Fluidized Beds,' Korean Chem. Eng. Res., 46, 451-464(2008)
  5. Ribeiro, C. P., "On the Estimation of the Regime Transition Point in Bubble Columns, " Chem. Eng. J., 140, 473-482(2008) https://doi.org/10.1016/j.cej.2007.11.029
  6. Wallis, G. B., One-Dimensional Two-Phase Flow, McGraw-Hill, New York(1969)
  7. Zuber, N. and Findlay, J. A., 'Average Volumetric Concentration in Two-Phase Flow Systems,' J. Heat Transfer Trans., C87, 453-468(1965)
  8. Masliyah, J. H., "Hindered Setting in a Multi-Species Particle System," Chem. Eng. Sci., 34, 1166-1168(1979) https://doi.org/10.1016/0009-2509(79)85026-5
  9. Song, S. M., Shin, I. S., Kang, Y., Cho, Y. J. and Yang, H. C., 'Characteristics of Heat Transfer in Three-Phase Swirling Fluidized Beds,' Korean Chem. Eng. Res., 46, 56-62(2008)
  10. Ruzika, M. C., Grahos, J. and Teixeira, J. A., "Effects of Viscosity on Homogeneous-Heterogeneous Flow Regime Transition in Bubble Columns," Chem. Eng. J., 96, 15-22(2003) https://doi.org/10.1016/j.cej.2003.08.009
  11. Pohorecki, R., Moniuk, W., Zdrojkowski, A. and Bielski, P., "Hydrodynamics of a Pilot Plant Bubble Column under Elevated Temperature and Pressure," Chem. Eng. Sci., 56, 1167-1174(2001) https://doi.org/10.1016/S0009-2509(00)00336-5
  12. Kantarci, N., Borak, F. and Ulgen, K. O., "Bubble Column Reactors," Proc. Biochem., 40, 2263-2283(2005) https://doi.org/10.1016/j.procbio.2004.10.004
  13. Banisi, S. and Finch, J. A., 'Reconciliation of Bubble Size Estimation Methods Using Drift Flux Analysis', Miner. Eng., 7, 1555-1559(1994)
  14. Ityokumbul, M. T., Salama, A. I. A. and Taweel, A. M., 'Estimation of Bubble Size in Flotation Columns,' Miner. Eng., 8, 77-89 (1995)
  15. Zou, R., Jiang, X., Li, B., Zu, Y. and Zhang, L., "Studies on Gas Holdup in a Bubble Column Operated at Elevated Temperatures," Ind. Eng. Chem. Res., 27(10), 1910-1916(1988) https://doi.org/10.1021/ie00082a025