Experiments on the droplet field in multiphase pipe flow
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Gas-liquid flows are very common in industrial applications and many times involve three phases. Experiments are important as basis for development of 1D flow models used for design of multiphase transport systems. The experiments are either used as direct closure relation or for model validation. Currently, there is a lack of three-phase flow data on droplet entrainment. This thesis is focused on two main topics: establish relevant experimental data of the droplet flux profiles, pressure gradient and flow characteristics of three-phase stratified and annular flows and to develop instrumentation suitable for three phase flow measurements. Experiments in three phase flows at high gas densities were conducted to obtain the magnitude and distribution of the droplet field flux and the effect of the water as a second liquid phase. This was studied by sampling the droplets using an isokinetic sampling probe. An automated probe system was designed and implemented successfully to reach this goal. The probe system is capable to conduct simultaneous measurements of the local droplet flux and gas velocity. Oil and water distribution inside the liquid layer in stratified-annular horizontal flow was studied using a two-energy traversing gamma densitometer and visual observations, using high speed video recordings of the flow. The experiments were performed at the Medium scale loop at SINTEF Multiphase Flow Laboratory using a high density gas at medium pressure conditions, oil and water. Based on the experimental results, an assessment of the effect of droplet flux distribution over the pipe cross section on the entrainment fraction calculation is discussed. Additionally, the current state of predicting models for liquid droplet concentration profiles is reviewed and new empirical correlations for the droplet concentration at the interface and the concentration decay are proposed. The effect on the pressure gradient changes due to liquid film at the wall, caused by droplet wetting, was studied on a second experimental setup. The setup was built at the NTNU Multiphase Flow Laboratory and consists of a vertical pipe to promote film symmetry. Twophase flow experiments using water and air and a viscous oil and air at atmospheric pressure were carried out. The results were compared with predictions of commercial flow simulators. In addition a new two-energy gamma densitometer is designed and built to obtain cross-sectional measurements of the phase fractions, capture transient flow conditions and for three-phase flow measurements (oil, water and gas) in acrylic pipes. This instrument will be further tested and applied in the future.