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Showing papers on "Slug flow published in 2017"


Journal ArticleDOI
TL;DR: A comprehensive review of 3947 published experimental data points for gas-liquid flow maps in vertical pipes and annuli, including a critical analysis of state-of-the-art measurement techniques used to identify bubble, slug, churn and annular flow regimes is provided in this article.

115 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of manifold design, channel design, the location of inlet and outlet connections to the heat exchanger along with the use of secondary header has been discussed for both single and two-phase flow.
Abstract: The presence of non-uniformities in the channels of a heat exchanger due to poor design of manifold and channel parameters has been the focus of the present paper. Unequal flow distribution results in an increased flow resistance leading to increased pumping power. It also leads to an imbalance of thermal characteristics due to the different mass flow rate in individual channels. The influence of manifold design, channel design, the location of inlet and outlet connections to the heat exchanger along with the use of secondary header has been discussed for both single and two-phase flow. The current achievements in the analytical modeling of such flow distributing manifolds have also been discussed supporting the numerical and experimental literature. In general, larger manifold area and a longer channel length are found to be resulting in better flow distribution. The use of secondary header results in higher pressure loss but this loss is offset by the increased flow uniformity. Two-phase flow behavior in distributing manifold is experimentally determined to be slug flow as a dominating behavior with occasional reverse flow. These non-uniformities must be taken into consideration for the proper design of heat exchangers, thus improving the performance of thermal systems.

70 citations


Journal ArticleDOI
TL;DR: In this article, a gas-liquid slug two-phase flow in a horizontal pipe was carried out to investigate the initiation and flow development mechanisms, and the slug initiation mechanisms were explained by visual observation and pressure fluctuations.

68 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of Dean vortices and 90° bends on gas-liquid mass transfer has been investigated and described, and it was shown that MCFI offers up to 14% higher conversion in comparison to other capillary setups.

62 citations


Journal ArticleDOI
Zhiqiang Yang1, Maoqiong Gong1, Gaofei Chen1, Xin Zou1, Jun Shen1 
TL;DR: A detailed experimental study was carried out to investigate the flow boiling heat transfer and pressure drop characteristics of R600a in a smooth horizontal tube with an inner diameter of 6.mm.

60 citations


Journal ArticleDOI
TL;DR: In this paper, a comparative study of wire-mesh sensors and ultrafast X-ray tomography was conducted to investigate two-phase flows with high spatial and temporal resolution.

60 citations


Journal ArticleDOI
TL;DR: In this article, the mass transfer coefficient in liquid-liquid slug flow inside a square microchannel (MC-1, aspect ratio 1) and a rectangular microchannel with identical hydraulic diameter (400 µm) were investigated experimentally.

58 citations


Journal ArticleDOI
TL;DR: In this paper, the authors analyzed adiabatic gas-liquid Taylor flow in a square minichannel of 1.0mm hydraulic diameter using water, water-glycerol, or water-ethanol mixtures as liquid phase and hydrogen or nitrogen as gas phase to cover a broad range of material parameters.

54 citations


Journal ArticleDOI
TL;DR: In this article, the effects of hydraulic diameter of the square microchannels, flow rates, and physical properties, e.g., interfacial tension and the viscosities of the aqueous and organic phases on flow pattern transitions were clarified.

54 citations


Journal ArticleDOI
Lin Ding1, Bohui Shi1, Xiaofang Lv1, Yang Liu1, Haihao Wu1, Wei Wang1, Jing Gong1 
TL;DR: In this paper, a series of experiments were conducted in a gas-emulsion multiphase flow system using a high pressure flow loop, and the properties of hydrate agglomeration and deposition in different flow patterns were investigated.
Abstract: As oil/gas exploitation moves into deep water, hydrate formation and plugging in flowline have been a main concern of the flow assurance engineers. A series of experiments were conducted in a gas-emulsion multiphase flow system using a high pressure flow loop. The properties of hydrate agglomeration and deposition in different flow patterns were investigated. First, based on the hydrate chord length distribution and the changes of slurry density, several methods were proposed to quantitatively estimate the hydrate agglomeration degree and deposition degree. Second, typical results in each flow pattern were analyzed, and the plug formation mechanisms in each flow pattern were proposed. Then, after comparing the results in each flow pattern, it was found that the order of hydrate agglomeration degree from high to low is slug flow, stratified flow, bubble flow, and annular flow; and the order of hydrate deposition degree from high to low is annular flow, slug flow, bubble flow, and stratified flow.

45 citations


Journal ArticleDOI
TL;DR: In this article, the periodic pseudo-slug structures were visualized and the effect of liquid viscosity on the visualized structures was also presented, as well as the measurements of important hydrodynamic characteristics such as cross-sectional averaged void-fraction time series and mean void fraction.

Journal ArticleDOI
TL;DR: In this article, a novel approach for dual-modality electrical resistance and capacitance tomography (ERT-ECT) was proposed to visualize gas-oil-water flow in horizontal pipeline.
Abstract: Employing dual-modality tomography inherently involves data from multiple dimensions, and thus a coherent approach is required to fully exploit the information from various dimensions. This paper describes a novel approach for dual-modality electrical resistance and capacitance tomography (ERT-ECT) to visualize gas–oil–water flow in horizontal pipeline. Compared with the conventional methods with dual-modality tomographic systems, the approach based on thresholding takes the account of multi-dimensional data, which therefore is capable of providing insights into investigated flow in both spatial and temporal terms. The experimental results demonstrate the feasibility of the approach, by which six common flow regimes in horizontal pipeline flow are visualized based on the multi-dimensional data with ERT-ECT systems, including (wavy) stratified flow, plug flow, slug flow, annular flow, and bubbly flow. Although the present approach is proposed for data acquired with an ERT-ECT system, it is potentially adaptable to other dual-modality tomographic systems that use concentration tomograms as inputs.

Journal ArticleDOI
TL;DR: In this paper, a physics-based model for the fluid mechanics and heat transfer associated with slug flow boiling in horizontal circular microchannels is proposed, which is based on the widely used three-zone model of Thome et al. (2004).

Journal ArticleDOI
TL;DR: In this article, heat transfer process in different flow patterns is studied by employing the thermal boundary theory and new expressions for the heat transfer coefficient in various flow patterns have been proposed, such as bubble flow, slug flow and annular-mist flow.

Journal ArticleDOI
TL;DR: To nonintrusively measure the flow velocity of horizontal gas–liquid two-phase flow, an ultrasonic Doppler sensor and a conductance sensor with dedicated measurement models are presented.
Abstract: Flow velocity is an important process parameter that quantifies the volume or mass flow rate as well as monitors the process safety. To nonintrusively measure the flow velocity of horizontal gas–liquid two-phase flow, an ultrasonic Doppler sensor and a conductance sensor with dedicated measurement models are presented. The air superficial flow velocity can be directly obtained and the water superficial flow velocity can be calculated through a two-fluid model for bubble flow and plug flow. For slug flow, a correlation between the phase velocity in slug body and overall superficial flow velocity was built based on a slug closure model. In order to eliminate the influence of the changing velocity profile in the fluid, the sample volume was designed to cover the whole pipe cross section by installing a two-chip piezoelectric transducer with 1-MHz center frequency at the bottom of the pipe. The conductance sensor provided water holdup estimate to compensate the velocity measurement model. Experiments were carried out in a 50-mm inner diameter pipe to verify the proposed sensor and model. Three flow patterns (bubble flow, plug flow, and slug flow) were generated by adjusting the inlet flow rate of the air and the water. The results show that the mean relative error can achieve within 5%.

Journal ArticleDOI
TL;DR: In this article, the authors used a validated Computational Fluid Dynamics (CFD) approach to simulate the motion of Taylor bubbles in pipes; the interface is tracked with a Level-Set method implemented in a commercial code.

Journal ArticleDOI
TL;DR: In this article, the effect of header and channels orientations on the two-phase flow distribution in parallel micro-channels was investigated and it was found that the phase distribution characteristics of 2-phase flow splitting in parallel channels highly depended on the inlet flow patterns and the orientations of header.

Journal ArticleDOI
TL;DR: In this article, a multiphase flow profile inside a helically coiled tubular device (HCTD) was observed by using a high-speed camera, and the modular design of a specific type of HCTD, that is, the coiled flow inverter (CFI), was elucidated by the representation of a new design space diagram.
Abstract: A multiphase flow profile inside a helically coiled tubular device (HCTD) was observed by using a high-speed camera. Gas–liquid slug flow observations revealed that the Taylor vortices are influenced by secondary flow due to the centrifugal force acting perpendicular to the flow direction. Hence, mixing inside the liquid slug is enhanced by the combination of Dean and Taylor vortices in HCTD. The modular design of a specific type of HCTD, that is, the coiled flow inverter (CFI) is elucidated by the representation of a new design space diagram. Continuous precipitation of calcium carbonate (CaCO3) was investigated for modular CFI made of polyvinyl chloride (PVC) tubes (di = 3.2 mm) with slug flow patterns. CaCO3 was continuously precipitated along CFI with a conversion of ca. 90%. CFI provided a narrower particle size distribution with median particle diameters around 28 μm and more uniform morphology in comparison to a batch reactor.

Journal ArticleDOI
TL;DR: In this paper, the authors developed a one-dimensional slug flow model to reproduce thermal and hydrodynamic phenomena in oscillating heat pipes (OHPs) and found that the vapor volume oscillated with the same frequency as the pressure, and the vapor plug obtained energy or performed work depending on the direction of pressure propagation.

Journal ArticleDOI
TL;DR: In this article, the slug characteristics were acquired and computed using non-intrusive optical based technique and statistical analysis for the translational slug velocity and slug body length was conducted.

Journal ArticleDOI
TL;DR: In this article, the gas-liquid two-phase flow and mass transfer with fast chemical reaction in a microchannel were investigated experimentally, and it was shown that the bubble volume decreased exponentially with its movement along the channel in a quickly reactable absorbent.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the influence of square microchannel size on hydrodynamics and mass transfer in the liquid-liquid slug flow regime and found that decreasing the micro channel size improved the interfacial area due to plug length enlargement and deteriorated mass transfer resistances because of augmented internal circulations.
Abstract: The present study investigated the influence of square microchannel size on hydrodynamics and mass transfer in the liquid-liquid slug flow regime. Three square microchannels with the hydraulic diameters of 200, 400 and 600 µm were used. The employed method for estimating mass transfer coefficients remarkably increased the accuracy of the results. The findings revealed that decreasing the microchannel size improved the interfacial area due to plug length enlargement and deteriorated mass transfer resistances because of augmented internal circulations, leading to the considerable enhancement of mass transfer coefficients. The increasing effect on the overall mass transfer coefficient became greater with flow velocity, showing that size effect on mass transfer resistances was more profound at higher flow velocities. The influence of size on the interfacial area was significantly greater than that on mass transfer resistances due to the significant increment of wall film length with the decrease in channel size. This article is protected by copyright. All rights reserved.

Journal ArticleDOI
TL;DR: In this paper, a parametric study of isolated gas Taylor bubbles flowing in co-current with liquid in circular milli-and microchannels is presented, in a wide range of dimensionless numbers and some factors have not been properly addressed, such as the role of the Reynolds number, features of recirculation regions in the liquid slug and the liquid film development length.
Abstract: A deep knowledge of the hydrodynamics of two-phase flow in millichannels and microchannels is relevant to the design and control of micro structured equipment. While there is plenty of work published in this area, there is a lack of studies over a wide range of dimensionless numbers and some factors have not been properly addressed, such as the role of the Reynolds number, the features of recirculation regions in the liquid slug and the liquid film development length. Therefore, a wide range parametric study of isolated gas Taylor bubbles flowing in co-current with liquid in circular milli- and microchannels is presented, in a wide range of Capillary (CaB) (0.01–2) and Reynolds numbers (ReB) (0.01–700). The shape and velocity of the bubbles are, together with the flow patterns in the flowing liquid, analyzed and compared with numerical and experimental correlations available in the literature. For low values of CaB, the streamlines (moving reference frame (MRF)) in the liquid slug show semi-infinite recirculations occupying a large portion of the cross-section of the channel. The mean velocity of the fluid moving inside the external envelope of the semi-infinite streamlines is equal to the bubble velocity. For high values of CaB, there are no recirculations and the bubble is moving faster or at least at the velocity of the liquid in the center of the tube; this flow pattern is often called bypass flow. The results also indicate that the liquid film surrounding the bubbles is for low CaB and ReB numbers almost stagnant, and its thickness accurately estimated with existing correlations. The stagnant film hypothesis developed provides an accurate approach to estimate the velocity of the bubble, in particular for low values of CaB. The asymptotic behavior of the studied parameters enables the extrapolation of data for CaB lower than 0.01. In addition to the simulations of isolated bubbles, simulations with two consecutive bubbles were also carried out; coalescence was only observed in very specific conditions. The results obtained in this study are directly applicable to co-current slug flow in milli- and microchannels for 0.1 < ReB < 1000 and 0.02 < CaB < 2.

Journal ArticleDOI
Chao Dang1, Li Jia1, Mingchen Xu1, Qian Huang1, Qi Peng1 
TL;DR: In this article, the flow boiling characteristics of pure refrigerant R134a and zeotropic mixture R407C are experimentally investigated in a single visualized rectangular micro-channel heated on three sides with the cross-sectional area of 1mm × 1mm and length of 106mm.

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the mechanism responsible for plug to slug transition and associated dynamics of bubble detachment from the elongated bubble using flow visualization and local velocity measurements using FASTCAM Photron camera and a 3D automated traverse system.

Journal ArticleDOI
TL;DR: In this paper, a broad range of two-phase flow conditions, including bubbly, dispersed and slug flow, were tested in a clamped-clamped straight horizontal pipe, and the vibration response of both transversal directions for two span lengths was measured.

Journal ArticleDOI
TL;DR: In this article, the void fraction and pressure drop of gas-liquid slug flow in a circular microchannel were measured using a high-speed video camera and image processing method, and the measured data were compared with the existing and newly developed models.

Journal ArticleDOI
TL;DR: In this article, a tubular micro-reactor (TMR) was used to produce biodiesel with high conversion rate of up to 99% with only 4 min of residence time.
Abstract: The aim of this paper is to present an alternative to conventional biodiesel production by taking advantage of the flow patterns formed in micro-reactors. Biodiesel production was carried out 15 times faster in a tubular micro-reactor (TMR) than a well-mixed batch reactor (BR), achieving conversions up to ∼99% with 4 min of residence time. The experimental results were analyzed using dimensionless numbers and computational fluid dynamics (CFD) simulations. The CFD results showed that under the conditions used in the present study, the slug flow pattern can be expected, and this could explain the high conversion (>90%) reached in the TMR without using high methanol-oil molar ratios. The internal movement (auto-mixing) in the slug enhanced the mass transfer. Moreover, CFD simulations showed that at low conversion (<25%), the internal velocity of the oil slug will be the key factor related to the reactor performance.

Journal ArticleDOI
TL;DR: In this paper, the authors examined the influence of the presence of sodium dodecyl sulfate (SDS) on hydrodynamics and mass transfer in liquid-liquid slug flow inside a circular microchannel.
Abstract: Liquid-liquid slug flow inside a circular microchannel was studied experimentally to examine the influence of the presence of sodium dodecyl sulfate (SDS) on hydrodynamics and mass transfer. The microchannel was made of polytetrafluoroethylene (PTFE), with the internal diameter of 0.6 mm. The applied method for estimating mass transfer coefficients considerably increased the accuracy of the results. The findings revealed that the presence of SDS in the aqueous phase decreased the slug length of both phases due to the decrement of the interfacial tension, leading to the enhancement of the specific interfacial area. However, improved recirculations inside the slugs were mainly responsible for the enhanced mass transfer. The influence of SDS on internal circulations was remarkably greater than that on the interfacial area. Although the mass transfer coefficients were augmented with the SDS concentration, the increasing effect was levelled off at higher concentrations. Accordingly, a new correlation relating the overall volumetric mass transfer coefficient to Capillary number, Reynolds number and SDS concentration was proposed.

Journal ArticleDOI
TL;DR: In this article, a simultaneous visualization and measurement study has been carried out to investigate the flow boiling and two-phase flow instabilities of ammonia in a mini-channel evaporator at various heat and mass fluxes.