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- Cao, Zhen, et al.
(författare)
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Water-oil flow in square microchannels with a crossed junction
- 2018
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Ingår i: Fluid Machinery; Erosion, Slurry, Sedimentation; Experimental, Multiscale, and Numerical Methods for Multiphase Flows; Gas-Liquid, Gas-Solid, and Liquid-Solid Flows; Performance of Multiphase Flow Systems; Micro/Nano-Fluidics. - 9780791851579 ; 3
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Konferensbidrag (refereegranskat)abstract
- In the present study, water-oil flow patterns and slug hydrodynamics were experimentally studied in square glass microchannels with various hydraulic diameters (Dh = 600 µm, 400 µm, 200 µm). The aqueous phase is the continuous phase while the organic phase is the dispersed phase. The ranges of flow rates of the continuous phase and the dispersed phase are 0-200 ml/h and 0-12 ml/h, 0-120 ml/h and 0-6 ml/h, and 0-60 ml/h and 0-2 ml/h in the microchannels with Dh = 600 µm, 400 µm and 200 µm, respectively. The results show that the hydraulic diameter has significant effects on flow patterns and three main flow patterns are observed, i.e., annular flow, slug flow and droplet flow. Generally, annular flow appeared at high flow rates of the dispersed phase and low flow rates of the continuous phase, while droplet flow appeared at low flow rates of the dispersed phase and high flow rates of the continuous phase. However, slug flow existed at comparable flow rates of the continuous and dispersed phases. A dimensionless analysis is carried out and a new dimensionless group including Weber number and Reynolds number is derived. The new defined dimensionless group performs well to develop a general flow pattern map. In addition, slug flow hydrodynamics are investigated as well in the present study, considering the slug length and slug velocity. Based on the present experimental results, a new scaling law is proposed to predict the slug length and it shows a good agreement with the experimental results. It has been widely reported that slug velocities depend linearly on the total flow rates of the two phases, which is consistent with the present study. The linear law provides a good prediction of the experimental slug velocities but different slopes are suggested in microchannels with different hydraulic diameters.
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| 2. |
- Matoušek, Václav, et al.
(författare)
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Threshold Criteria for Components of Predictive Model for Pipe Flow of Broadly-Graded Slurry
- 2018
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Ingår i: ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting. - : The American Society of Mechanical Engineers. - 9780791851579
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Konferensbidrag (refereegranskat)abstract
- Industrial slurries transported in pressurized pipelines often consist of particles of broad size distribution. The broad particle size distribution affects slurry flow behavior in a pipe. A four-component model (4CM) predicts the frictional pressure drop in pipe flow of broadly graded slurry. The model considers Newtonian carrying liquid and splits the broadly graded solids into fractions (components) each of which contributes to the pressure drop through its own dominating friction mechanism expressed by a particular sub-model in the 4CM. The sorting of the solids into the components (carrier, pseudo-homogeneous, heterogeneous, fully-stratified) must be based on appropriate criteria. For the sake of simplicity, the 4CM currently uses threshold sizes of particles to split the solids into 4 components.The goal of the present work is to analyze the existing criteria for the threshold between the pseudo-homogeneous component and heterogeneous component and for the threshold between the heterogeneous component and fully-stratified component. The analysis is based on a description of mechanisms governing particle support (suspension, deposition) of each particular solids component in slurry flow. It shows that the existing grain-size thresholds actually express certain proportions among threshold velocities of flow delimiting different slurry flow regimes. Such threshold velocities are the deposition-limit velocity, the initial-suspension velocity, and the full-suspension velocity. We discuss the proportions and demonstrate how properties (of liquid, solids, flow) and associated parameters additional to the grain size may influence the thresholds.The analytical results are supported by experimental results for flow of individual components in a laboratory loop.
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