scholarly journals Hydrodynamic characteristics of a two-phase gas-liquid flow upward through a fixed bed of spherical particles

2001 ◽  
Vol 66 (1) ◽  
pp. 53-64 ◽  
Author(s):  
Snezana Serbula ◽  
Velizar Stankovic
Keyword(s):  
Pressure Drop ◽  
Liquid Velocity ◽  
Fixed Bed ◽  
Particle Diameter ◽  
Packed Bed ◽  
Spherical Particles ◽  
Hydrodynamic Characteristics ◽  
Phase System ◽  
Relative Pressure ◽  
Two Phase

The influence of an electrochemically generated gas phase on the hydrodynamic characteristics of a three-phase system has been examined. The two-phase fluid, (gas-liquid), in which the liquid phase is the continuous one, flows through a packed bed with glass spheres. The influence of the liquid velocity was examined, as well as the gas velocity and particle diameter on the pressure drop through the fixed bed. It was found that with increasing liquid velocity (wl = 0.0162-0.03 m/s), the relative pressure drop decreases through the fixed bed. With increasing current density, the pressure drop increases, since greater gas quantities stay behind in the fixed bed. Besides, it was found that with decreasing diameter of the glass particles, the relative pressure drop also decreases. The relationship betweeen the experimentally obtained friction factor and the Reynolds number was established.

An Experimental Investigation of the Effect of Walls on Gas-Liquid Flows Through Fixed Particle Beds

2005 ◽  
Author(s):  
Marcia A. Cooper ◽  
Raymond O. Cote ◽  
Timothy J. O’Hern ◽  
John R. Torczynski ◽  
Lindsey R. Evans ◽  
...  
Keyword(s):  
Liquid Flow ◽  
Fixed Bed ◽  
Particle Diameter ◽  
Packed Bed ◽  
Spherical Particles ◽  
Two Phase ◽  
Order Unity ◽  
Flow Measurements ◽  
D Values ◽  
Particle Bed

The effect of particle diameter on downward co-current gas-liquid flow through a fixed bed of particles confined within a cylindrical column is investigated. Several hydrodynamic regimes that depend strongly on the properties of the gas stream, the liquid stream, and the packed particle bed are known to exist within these systems. This experimental study focuses on characterizing the effect of wall confinement on these hydrodynamic regimes as the diameter d of the spherical particles becomes comparable to the column diameter D (or D/d becomes order-unity). The packed bed consists of polished, solid, spherical, monodisperse particles (beads) with mean diameter in the range of 0.64–2.54 cm. These diameters yield D/d values between 15 and 3.75, so this range overlaps and extends the previously investigated range for two-phase flow. Measurements of the pressure drop across the bed and across the pulses are obtained for varying gas and liquid flow rates.

scholarly journals Hydrodynamics and axial mixing in a packed gas-liquid column

2003 ◽  
pp. 33-48
Author(s):  
Branislava Barjaktarovic ◽  
Milan Sovilj ◽  
Svetlana Popovic
Keyword(s):  
Pressure Drop ◽  
Gas Phase ◽  
Liquid Flow ◽  
Packed Column ◽  
Packed Bed ◽  
Axial Dispersion ◽  
Gas Absorption ◽  
Phase System ◽  
Two Phase ◽  
Gas Phases

The objective of this study was to investigate the pilot-plant gas absorption packed column hydrodynamics, as well as axial mixing in the system air-water. The pressure drop and the gas phase holdup data were determined in dependence on the flow rates of gas and liquid phases. The influence of superficial velocities of liquid and gas phases on the liquid axial dispersion in a gas-liquid packed bed column (ID 15 cm) consisting of Raschig rings (15x15x2 mm) were investigated. The pressure drop was measured with a U-type manometer, connected to the bottom and the top of the working part of the column. The gas phase holdup data in the air-water two-phase system was calculated as a ratio of the gas phase volume to the total volume of the two-phase system. Axial dispersion in the water phase has been determined by examining of the distribution of residence times of a salt tracer (NaCl) in the packed bed. The tracer was injected in the liquid flow above the packed bed; samples of liquid were simultaneously taken from two sites at 1 m distance along the bed. Salt concentrations in the samples were determined by conductivity measurements. The mean residence time and the axial dispersion number were calculated by the moment method. The axial dispersion increases with an increase of liquid flow velocities and decrease of superficial air velocities.

scholarly journals DEM--CFD modeling and simulations of hydrodynamic characteristics and flow resistance coefficient in fixed-bed reactors

2021 ◽  
Author(s):  
Yaping Li ◽  
Le Xie ◽  
Yonghua Zhou ◽  
Chongwen Jiang ◽  
Hong Zhong
Keyword(s):  
Pressure Drop ◽  
Flow Resistance ◽  
Fixed Bed ◽  
Resistance Coefficient ◽  
Spherical Particles ◽  
Hydrodynamic Characteristics ◽  
Model Parameters ◽  
Large Set ◽  
Fixed Bed Reactors ◽  
Fixed Beds

The ability to predict void fraction, pressure drop, and flow resistance coefficient in fixed-bed reactors is significant to their optimal design. In this study, the discrete element method (DEM) is combined with computational fluid dynamics (CFD) to simulate the hydrodynamic characteristics of fixed-beds. A realistic random packing structure for fixed-beds with spherical particles was generated via the DEM method and then meshed using Ansys ICEM software for the CFD simulation. A grid independency study was performed to select appropriate grid model parameters. A large set of numerical experiments was conducted to investigate the hydrodynamic characteristics with respect to different inlet velocities and particle sizes, and the simulated pressure drop data were used to calculate the flow resistance coefficient. The output flow resistance coefficients agreed well with those calculated by the classical models in laminar and turbulent flow regimes, thereby indicating the accuracy and advantage of the proposed DEM–CFD approach.

scholarly journals Effects of air-lift reactor dimensions on its hydrodinamic characteristics

2010 ◽  
Vol 64 (1) ◽  
pp. 35-46
Author(s):  
Milan Milivojevic ◽  
Danijela Andrejic ◽  
Branko Bugarski
Keyword(s):  
Liquid Velocity ◽  
Solid Particles ◽  
Hydrodynamic Characteristics ◽  
Solid Loading ◽  
Phase System ◽  
Two Phase ◽  
Liquid Circulation ◽  
Airlift Bioreactors ◽  
Circulation Velocity ◽  
Liquid Circulation Velocity

In this study the hydrodynamic characteristics of the external loop airlift bioreactors were investigated. The influence of reactor height and solid particles concentration on the mean liquid circulation velocity was examined. Also, the possibility of theoretical prediction of this liquid circulation velocity was assessed. The correlation originally proposed by Glennon et al. (Chem. Eng. Commun. 121 (1993) 183-192) for two phase system liquid velocity prediction was extended and corrected for application to three phase systems. The accuracy of this new correlation was tested on our experimental data. The corrected correlation shows higher accuracy than the originally proposed one. In addition, the influence of reactor geometry and solid loading on reactor working performances was established.

Prediction of Pressure Drop in Air-Water Two Phase Upflow Through Packed Bed

2010 ◽  
Author(s):  
Nan Zhang ◽  
Zhongning Sun
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Flow Model ◽  
Homogeneous Model ◽  
Great Influence ◽  
Particle Diameter ◽  
Predictive Ability ◽  
Packed Bed ◽  
Two Phase ◽  
Model Based

The resistance characteristics of air-water flow upward through packed bed have been studied experimentally. Experiments were conducted in transparent tube with 50mm inner diameter filled with glass spheres of which the diameters are 2, 5 and 8mm, respectively. Experimental results show that the pressure drop increases with the increasing of gas-liquid mass flow rate, and has a certain relationship with the flow pattern. The different particle diameter and porosity have great influence on pressure drop under the same flow condition. The applicability of several representative correlations for calculating the two-phase pressure drop and two new correlations were evaluated against 234 group experimental data. All compared correlations can be grouped into two, namely: (a) the separated flow model based on Lockhart & Matinelli method (b) the homogeneous model based on gas and liquid Reynolds number. The results show that: (1) the best agreement between measured and calculated values is obtained with the correlations based on separate flow model, but the predictive ability is reduced with the increasing of particle diameter. (2) the existing homogeneous model shows the considerable discrepancies with experiment values; however the modified homogeneous correlation by considering particle-to-column diameter ratio and porosity gives good agreement with experimental data.

Single Phase and Two-Phase Flow Pressure Drop in Pebble Beds

2010 ◽  
Author(s):  
Bofeng Bai ◽  
Maolong Liu ◽  
Xiaofei Lv ◽  
Wang Su ◽  
Xiao Yan ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Gas Phase ◽  
Single Phase ◽  
Two Phase Flow ◽  
Particle Diameter ◽  
Spherical Particles ◽  
Phase Flow ◽  
Two Phase ◽  
Pressure Drops ◽  
Flow Pressure

An experimental study was conducted on the pressure drop of single phase and air-water two-phase flow in the bed of rectangular cross sections filled with uniform spheres densely. In the present flow-regime model, the bed was subdivided into a near-wall region and a central region. And a new empirical correlation for the prediction of single-phase flow pressure drops was proposed based on the model. The correlation can be used to predict the single phase pressure drop for both great tube-to-particle diameter ratio packed beds and small tube-to-particle diameter ratio packed beds and for the pebble beds packing with spherical particles and non spherical particles. A new empirical correlation for the prediction of two-phase flow pressure drops was proposed based on the gas phase relative permeability as a function of the gas phase saturation and the void fraction. The correlation fit well also for both experimental data points of spherical particles and non spherical particles.

scholarly journals Influence of Macroscopic Wall Structures on the Fluid Flow and Heat Transfer in Fixed Bed Reactors with Small Tube to Particle Diameter Ratio

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 689
Author(s):  
Thomas Eppinger ◽  
Nico Jurtz ◽  
Matthias Kraume
Keyword(s):  
Heat Transfer ◽  
Fixed Bed ◽  
Particle Diameter ◽  
Diameter Ratio ◽  
Spherical Particles ◽  
Reactor Wall ◽  
Entry Length ◽  
Fixed Bed Reactors ◽  
Wall Structures ◽  
Small Tube

Fixed bed reactors are widely used in the chemical, nuclear and process industry. Due to the solid particle arrangement and its resulting non-homogeneous radial void fraction distribution, the heat transfer of this reactor type is inhibited, especially for fixed bed reactors with a small tube to particle diameter ratio. This work shows that, based on three-dimensional particle-resolved discrete element method (DEM) computational fluid dynamics (CFD) simulations, it is possible to reduce the maldistribution of mono-dispersed spherical particles near the reactor wall by the use of macroscopic wall structures. As a result, the lateral convection is significantly increased leading to a better radial heat transfer. This is investigated for different macroscopic wall structures, different air flow rates (Reynolds number Re = 16 ...16,000) and a variation of tube to particle diameter ratios (2.8, 4.8, 6.8, 8.8). An increase of the radial velocity of up to 40%, a reduction of the thermal entry length of 66% and an overall heat transfer increase of up to 120% are found.

scholarly journals Gas-liquid flows through porous media in microgravity: Packed Bed Reactor Experiment-2

2021 ◽  
Author(s):  
Brian Motil ◽  
Mahsa Taghavi ◽  
Vemuri Balakotaiah ◽  
Henry Nahra
Keyword(s):  
Gas Flow ◽  
Liquid Velocity ◽  
Space Station ◽  
Particle Diameter ◽  
Packed Bed ◽  
Packed Bed Reactor ◽  
Flow Rates ◽  
Test Conditions ◽  
Superficial Gas Velocity ◽  
Liquid Flows

Experimental results on pressure drop and gas hold-up for gas-liquid flow through packed beds obtained from a second flight on the International Space Station are presented and analyzed. It is found that the gas hold-up is a function of the bed history at low liquid and gas flow rates whereas higher gas hold-up and pressure gradients are observed for the test conditions following a liquid only pre-flow compared to the test conditions following a gas only pre-flow period. Over the range of flow rates tested, the capillary force is the dominant contributor to the pressure gradient and is found to be linear with the superficial liquid velocity but is a much weaker function of the superficial gas velocity. The capillary contribution is also a function of the particle size and varies approximately inversely with the particle diameter within the range of the test conditions.

scholarly journals Frictional Pressure Drop and Liquid Holdup of Churn Flow in Vertical Pipes with Different Viscosities

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Zilong Liu ◽  
Yubin Su ◽  
Ming Lu ◽  
Zilong Zheng ◽  
Ruiquan Liao
Keyword(s):  
Pressure Drop ◽  
Liquid Velocity ◽  
Gas Velocity ◽  
Liquid Holdup ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Viscous Oil ◽  
Predicted Values ◽  
Superficial Gas Velocity ◽  
Churn Flow

Churn flow commonly exists in the pipe of heavy oil, and the characteristics of churn flow should be widely understood. In this paper, we carried out air and viscous oil two-phase flow experiments, and the diameter of the test section is 60 mm. The viscosity range of the oil was 100~480 mPa·s. Based on the measured liquid holdup and pressure drop data of churn flow, it can be concluded that, due to the existence of liquid film backflow, positive and negative frictional pressure drop can be found and the change of frictional pressure drop with the superficial gas velocity is related to superficial liquid velocity. With the increase of viscosity, the change rate of frictional pressure drop increases with the increase of the superficial gas velocity. Combining our previous work and the Taitel model, we proposed a new pressure drop model for viscous oil-air two-phase churn flow in vertical pipes. By comparing the predicted values of existing models with the measured pressure drop data, the proposed model has better performance in predicting the pressure drop.

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