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

The Korean Society of Mechanical Engineers (대한기계학회)
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3D Numerical Study of Horizontal Falling Film Evaporator in Multi Effect Distillation (MED) Plant

MED 담수기내 수평관 강하막식 증발기의 3D 수치해석적 연구

  • Kim, Soo Jae (Dept. of Mechanical Engineering, Pohang University of Science and Technology) ;
  • Je, Junho (Division of Advanced of Nuclear Engineering, Pohang University of Science and Technology) ;
  • Kim, Moo Hwan (Division of Advanced of Nuclear Engineering, Pohang University of Science and Technology)
  • 김수재 (포항공과대학교 기계공학부) ;
  • 제준호 (포항공과대학교 첨단원자력공학부) ;
  • 김무환 (포항공과대학교 첨단원자력공학부)
  • Received : 2012.12.31
  • Accepted : 2013.01.17
  • Published : 2013.05.01
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Abstract

In the present work, a numerical study of a horizontal falling film evaporator in a multi-effect distillation (MED) plant is performed. Tube bundles in the evaporator are described as porous media, and a volume-averaged method is applied. To calculate the fluid flow and phase change in the evaporator due to heat transfer in the system, FLUENT and user-defined functions (UDF) are used. To observe the performance of the evaporator under different operational conditions, tests are conducted for a steam mass flux ranging from 0.5 to 2.5 $kg/m^2s$ in the horizontal tube, for mass fraction of the noncondensable gas in the tube inlet ranging from 0% to 1%, and for film Reynolds numbers ranging from 100 to 1,000 for the falling film. The evaporation rate increases with the steam mass flux and Reynolds number. In contrast, the evaporation rate decreases by 0.87% with a 1% increase in the mass fraction of the noncondensable gas in the tube.

본 연구에서는 다중효용 증발식 담수기에 쓰이는 강하막식 증발기의 수치해석을 수행하였다. 증발기에 사용되는 다관군을 다공성 매질로 묘사하고 공간평균 개념을 적용하였다. 증발기 내부의 유동계산 및 열 전달로 인한 상변화를 계산하기 위해서 FLUENT 와 UDF 가 사용되었다. 작동조건에 대한 증발기의 성능변화를 살펴보기 위해 수평관 내 증기 질량 유속을 $0.5{\sim}2.5kg/m^2s$, 관내입구 측 비 응축성 기체의 질량분율을 0~1%, 그리고 수평관 외 뿌려지는 강하막의 액막 레이놀즈 수를 100~1000 으로 바꾸어가며 해석을 수행하였다. 관내 증기유속 및 관외 강하막 레이놀즈 수가 증가할수록 증발량은 증가하였으며, 관내 비 응축성 기체의 질량분율이 1%증가함에 따라 증발량이 0.87%줄어들었다.

Keywords

References

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