Three quantities were measured to provide a database for validation of computations with a CFD (computational fluid dynamics) code. The quantities were the radial temperature distributions of steam-air mixture in a vertical circular pipe (diameter, 49.5 mm), the temperature gradients in the pipe wall (thickness, 5.5 mm) and the radial temperature distributions of the cooling water in the annulus gap (8.25 mm) outside the pipe. From these temperature distributions, three kinds of condensation heat fluxes were obtained from the enthalpy decreasing rate of the steam-air mixture based on the assumption of saturated conditions, the temperature gradient in the pipe wall, and the enthalpy increasing rate of the cooling water. These three heat fluxes were different especially in the downstream region, where the heat flux was low, so that the average of the three heat fluxes was used to evaluate factors affecting the condensation heat transfer. This average was expressed by a function of the steam density difference between the main flow of the mixture and the mixture on the wall surface, the average steam velocity and the thermal boundary layer thickness. The suction effect due to condensation was also discussed.

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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,(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.