Flow regime identification for upward two-phase flow in helically coiled tubes

Zhu, Hongye; Li, Zhaoxu; Yang, Xingtuan; Zhu, Guangyu; Tu, Jiyuan; Jiang, Shengyao

doi:10.1016/j.cej.2016.09.100

Cited by 54 publications

(33 citation statements)

References 32 publications

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“…En flujos bifásicos helicoidales la mayoría de los estudios están enfocados a casos en los que se analizan sistemas líquido-gas frecuentemente ligados al funcionamiento o diseño de intercambiadores de calor (Vashisth y Nigam, 2009;Zhu et al, 2017). Dado que entre líquidos y gases existen normalmente grandes diferencias de densidad, viscosidad y energía superficial, los resultados de dichos estudios tienen una extrapolación limitada a otros sistemas como los formados por dos líquidos (Vidnes et al, 2015), en los que las diferencias entre las variables indicadas pueden ser de otro orden de magnitud.…”

Section: Introductionunclassified

Un estudio sobre el rendimiento de separación de tubos helicoidales aplicados a flujos bifásicos de agua y aceite de oliva

Vallesquino¹,

Molina²

2019

ing.agua

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<p>Los estudios sobre flujos bifásicos de agua y aceite, desarrollados con separadores helicoidales, no son numerosos y parecen estar restringidos, actualmente, a la industria petroquímica. El presente trabajo ha sido realizado para estudiar el comportamiento de estos dispositivos cuando son empleados con dispersiones de agua y aceite de oliva a diferentes concentraciones. A tal fin, se han construido dos modelos experimentales para analizar los rendimientos de separación alcanzados bajo diferentes condiciones de funcionamiento. Se han tenido en cuenta variables como el número de Reynolds, las pérdidas de carga o la relación entre flujos descargados para determinar su rango óptimo de operación. Los resultados obtenidos indican que en sistemas de agua-aceite de oliva es posible obtener rendimientos de separación cercanos al 100% con tuberías de diámetro pequeño, radios de hélice reducidos y bajos requerimientos energéticos. Este hecho abre una vía para diseñar estos dispositivos desde otros puntos de vista.</p>

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Section: Introductionunclassified

Un estudio sobre el rendimiento de separación de tubos helicoidales aplicados a flujos bifásicos de agua y aceite de oliva

Vallesquino¹,

Molina²

2019

ing.agua

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“…The experimental flow regime identification was based solely on the X-ray radiography measurements and the resulting postprocessed quantitative void fraction data. According to the methodology introduced by Zhu et al (2017), the 136 measurements were classified into six different flow regimes, namely bubbly, plug, slug, wavy, slugannular, and annular flow. More detailed information of the facility and experimental procedures are reported by Zhuang et al (2018) and Breitenmoser et al (2019).…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, detailed information on pressure drops, void fraction distributions and flow regime in helical coil geometries are relevant as well. Experiments on two-phase flow in vertical helical coils have been performed in the past (Kasturi and Stepanek, 1972;Xin et al, 1996;Mandal and Das, 2003;Zhu et al, 2017) to investigate pressure losses, void fraction and flow regimes and corresponding empirical correlations have been proposed.…”

Section: Introductionmentioning

confidence: 99%

CFD Simulation of Two-Phase Flows in Helical Coils

et al. 2020

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The behavior of two-phase flow and corresponding flow regimes in helical tubes significantly differ when compared to two-phase flows in straight tubes due to centrifugal and torsion effects. In order to gain physical insight and gather data for validating computational models, a large number of experiments were performed on a helical coil experimental setup operated with a mixture of water and air. The experimental data were used to assess the predictive capabilities of current two-phase Computational Fluid Dynamics (CFD) models based on the Volume of Fluid (VOF) approach. In the present paper, a comparison of the CFD simulation results with the high-resolution experimental data is discussed, with special emphasis on two-phase pressure drops and void fraction distributions. It is shown that the CFD VOF model is able to correctly capture the occurrence of five flow regimes observed in the experiments, namely bubbly flow, plug flow, slug flow, slug-annular flow, and annular flow. However, a good quantitative agreement for pressure drops and void fraction distributions is found in slug flow and slug-annular flow regimes only. The good agreement found only in a limited range of flow regimes demonstrates that there is not a single set of best-practice guidelines for CFD VOF models that can be applied across a wide range of two-phase flow regimes. Also, there is not a single mesh that can be used to simulate all of the flow regimes and a case-specific mesh and time-step convergence study is needed for each individual flow regime. In the current study, optimal mesh size and time step were obtained for a slug flow test case. Hence, good agreement was obtained only for similar flow regimes, leading to significant disagreement with experimental data for test cases with substantially different flow patterns.

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“…The effect of dry bubbles, which are cylindrical bubbles with poor wall wetting, shown by Kurt et al (2017) and Krieger et al (2020) was not found in this study. Zhu et al (2017) identified flow regimes for gas-liquid flows in vertical coiled tubes. One of the only flow field sketches for horizontal helical reactors on a micro-scale is shown by Kurt et al (2017).…”

Section: Introductionmentioning

confidence: 99%

Experimental characterization of mixing and flow field in the liquid plugs of gas–liquid flow in a helically coiled reactor

2021

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Flow mixing of two miscible liquids with the addition of gas bubbles is a process often found in industrial chemical apparatus for the production of primary matter. The ongoing optimization of such processes also involves the transformation of batch to continuous mode operation. In that case, the use of helically coiled tubes is an interesting alternative, since those reactors have narrow residence time distributions, very good radial mixing properties and excellent mass transfer can be realized between gases and liquids. For these reasons, in this study the mixing of two miscible liquids with addition of air bubbles in gas–liquid flows has been characterized in a horizontal helically coiled reactor in the laminar flow regime at $${\text{Re}}_{{{\text{total}}}} = 300 \ldots 1088$$ Re total = 300 … 1088 . Eight different superficial liquid velocities and five superficial gas velocities were investigated. In order to characterize mixing in the liquid plugs between two bubbles, laser-induced fluorescence of resorufin was used and particle image velocimetry has been employed to characterize the flow field. Pseudo-3D-visualizations of the resorufin concentration and the Q-criterion, representing the mixing efficiency and vorticity, respectively, were established for individual liquid plugs from the time-resolved measurement results. A time-resolved mixing coefficient, as well as a mean mixing coefficient obtained from multiple liquid plugs, is calculated from the fluorescence images for all examined flow conditions. The experimental results clearly show an increase in the mixing coefficient compared to single-phase conditions, caused by the bubbles. However, distinct mixing pattern, depending on the flow structure, can be recognized on different locations inside the liquid plug. Compared to a stationary case without air bubbles, mixing is worse behind the bubbles and increases inside the plug, reaching a maximum mixing coefficient in front of the next bubble. Overall the mixing coefficient is always increased by the presence of the bubbles. Pseudo-3D-visualizations of the Q-criterion and the vorticity show the presence of secondary vortices right in front of the bubbles, shifted to the outer tube walls, and in addition to the steady Dean vortices. In small plugs, these secondary vortices appear in the whole plug and increase the mixing coefficient drastically. Graphical Abstract

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Flow regime identification for upward two-phase flow in helically coiled tubes

Cited by 54 publications

References 32 publications

Un estudio sobre el rendimiento de separación de tubos helicoidales aplicados a flujos bifásicos de agua y aceite de oliva

Un estudio sobre el rendimiento de separación de tubos helicoidales aplicados a flujos bifásicos de agua y aceite de oliva

CFD Simulation of Two-Phase Flows in Helical Coils

Experimental characterization of mixing and flow field in the liquid plugs of gas–liquid flow in a helically coiled reactor

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