Effects of Fluid Properties on Countercurrent Flow Limitation in Vertical Pipes

To evaluate effects of the diameter on countercurrent flow limitation (CCFL) in vertical pipes, in our previous study, we classified CCFL into CCFL-L at the sharp-edged lower end, CCFL-U at the sharp-edged upper end, and CCFL-P inside the vertical pipe with round-edged upper and lower ends, and we found that the characteristic length in the Wallis parameter, w = D(1-β)Lβ (where D and L respectively denote the diameter and the Laplace capillary length), is respectively β = 0, 1 and β ≈ 0.5 for CCFL-L, CCFL-U and CCFL-P. In this study, we evaluated effects of fluid properties on CCFL in vertical pipes by using existing CCFL data. The most effective fluid properties is the liquid viscosity and we selected the viscosity ratio of gas and liquid (μG/μL) as a dimensionless parameter. From effects of μG/μL on the slope m and constant C in the Wallis correlation, we classified three regions of large positive interrelations of m and C with μG/μL for small μL (room-temperature to high-temperature water), small interrelations of m and C with μG/μL for medium μL (low-concentration glycerol water solution), and the large negative interrelation of m with μG/μL for large μL (high-concentration glycerol water solution). We obtained exponent functions of μG/μL for m and C in the case of the small μL (room-temperature to high-temperature water) for CCFL-L and CCFL-U except CCFL-P without high-temperature CCFL data.