Uncertainty analysis for multiphase flow: A case study for horizontal air-water flow experiments

This work describes the procedure used to define the measurement uncertainties of horizontal two-phase airwater flow experiments conducted to determine influences due to pipe diameter on pressure gradient on such flows. These experiments were performed with 4 different pipe diameters, always using the same test section length, therefore varying the length-to-diameter (L/D) ratio. Several parameters were measured, such as volumetric/mass flow rate, pressures, temperatures and pressure drop; other parameters were calculated, such as the superficial velocities of each fluid, as well as their corresponding properties. The main parameters studied were the flow patterns for different velocity configurations and the two-phase pressure drop to be used for model improvement, thus the importance of uncertainties analysis. The sources of uncertainty were defined, detailed, systematically studied and quantified. Also, the reproducibility capacity of the experimental setups were analysed through the uncertainty analysis and proving them to be able for future similar studies. The flow maps with their uncertainties could help understand the thresholds for each defined flow pattern region, and the plots of two-phase pressure drop variation with diameter confirmed the homogeneous model as a possible approach to calculate pressure drop if the uncertainties are considered.