The effect of gap size on counter current flow limitation phenomena in narrow annular gaps with large diameter

An experimental study on counter-current flow limitation phenomena in narrow annular passages was carried out. The gap sizes tested were 1,2 and 3 mm. This is very small compared with the outer diameter of the annular passage, 500 mm. It was visually observed that a CCFL might occur in some part of periphery while the other part is remained in a counter current flow pattern. That is, non-uniform behaviour of fluids due to a 2-dimensional effect appear in a large diameter facility. Because of this non-uniformity, a CCFL is defined in the present work as the situation where net water accumulation is sustained. That is, some amount of water should not be allowed to penetrate the gap and accumulate over the gap at CCFL criterion. The measured data are presented in the form of Wallis' type correlation with characteristic length of gap size. It was found that the present correlation is in good agreement with other empirical correlation based on measurements whose test section diameter is close and the gap size is much larger than that of the present test section