Counter-Current Flow Limit of a Vertical Two Phase (Water/Air) Flow

상반류(물/공기) 유동한계에 관한 연구

A set of experiments of Counter-Current Flow Limit(CCFL or Flooding) was performed to improve the drawbacks of Wallis' Correlation which neglects the effects of channel size, channel length, injection method and the boundary conditions at the inlet of liquid and gas phase. In these experiments using water and air, the followings were found ; (i) The effects of channel size and length were quite significant. In large tubes(D>20mm), the flooding front occurred at the bottom of the channel and when the gas flow increased the front moved upward ; however, in small tubes(D<20mm), there were no upward movement of flooding front and the flooding just occurred at the liquid inlet. (ii) The effect of water inlet device was not as significant as that of channel length though the inlet boundary conditions could affect the flow development and flooding afterward. (iii) Once the flooding front reached the inlet of water injection device, an newly reduced flow condition was set up and resulted in another flooding corresponding to the new condition.

본 연구에서는 CCFL에 영향을 미치는 관의 크기, 길이, 주입구 형상 등 변화 에 대한 현상해석과 이의 영향을 고려한 관계식의 개발에 있다. 그러므로 본 실험에 서의 물의 주입량을 관에 수막(film)이 형성시킬 수 있는 유량으로 고정시킨 상태에서 공기의 유량을 증가시켜, CCFL이 발생하였을때 공기와 물의 유량을 측정하였다. 그 리고 관의 길이, 크기 그리고 물의 주입구 구조(예각, 둔간, 톱니, 다공)의 변화에 따 른 CCFL의 영향에 관하여 실험을 수행하였다.