Gas-liquid two-phase interfacial flows, such as the liquid film flows (also known as wetting flows on walls), are observed in many industrial processes including absorption, desorption, distillation, and so on. The present study focuses on the characteristics of wetting flows, in particular the drastic transition between the film flow and rivulet flow, as the liquid flow rate and the wall surface texture treatments are varied. The three-dimensional gas-liquid two-phase interfacial flow (wetting flow) simulation is based on the volume of fluid (VOF) model. As the liquid flow rate is increased and then decreased, a hysteresis of the transition between the film flow and rivulet flow is discovered, which implies that the transition phenomenon depends primarily on the history of the change of interfacial surface shape (which affects the process of the flow pattern transition). The applicability and accuracy of the present numerical simulation is validated by using the existing experimental and theoretical studies. Further study on the effect of texture geometry shows that the surface texture treatments added on the wall can impede liquid channeling and increase the wetted area.
A wireless electrical resistance tomography (WERT) system has been developed for the realtime imaging particles distribution in centrifugal particles-liquid two-phase fields. The developed WERT system consists of 1) a constant-current injector; 2) a voltage measurement device; 3) two electrodes switching devices; 4) a wireless transmission device; 5) a microcomputer, and: 6) a host computer. The WERT system provides the advantages of miniaturization and wireless transmission as compared to the conventional wired electrical resistance tomography (ERT) systems. Consequently, we wirelessly imaged the real-time particles distribution in the lab-scale centrifuge in particles-liquid (glass beads-NaCl solution) two-phase flow qualitatively at various measurement positions under various rotational velocities. Based on the images, the particles volume fractions in the centrifugal field are measured quantitatively. The measured particles volume fractions at various measurement positions indicate parabolic separation interfaces between the particles-liquid phases, which are in good agreement with the numerical simulation by Euler-Euler method by an average deviation of 7.21%. As the rotational velocity is increased, particles are pushed outward to be raised along the lab-scale centrifuge because of the increased centrifugal force, which causes a sharper paraboloid interface. INDEX TERMS Real-time measurement, particles distribution, centrifuges, wireless electrical resistance tomography.
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