Investigation of Transition Boundary and Nature of Pulsating Flow in the Trickle Bed Reactors by Electrical Resistance Tomography

2013 ◽  
Author(s):  
Takeshi Eda ◽  
Achyut Sapkota ◽  
Jun Haruta ◽  
Masayuki Nishio ◽  
Masahiro Takei
Keyword(s):  
Liquid Flow ◽  
Electrical Resistance ◽  
Flow Condition ◽  
Pulsating Flow ◽  
Fixed Bed Reactor ◽  
Electrical Resistance Tomography ◽  
Liquid Distribution ◽  
Cross Sectional ◽  
Transition Boundary ◽  
Trickle Bed

A fixed bed reactor that operates in gas-liquid co-current down flow is called Trickle Bed Reactor (TBR). It is widely used in chemical engineering. And, recently used in purification of radioactive contamination from contaminated water generated in the Fukushima Daiichi nuclear power plant. There are several flow conditions that occur in the TBR due to gas and liquid flow rate. Since mass and heat transfer rate and particles wetting depend on flow condition, it is necessary to establish the visualization techniques to understand flow condition, transition boundary and properties of gas liquid flow in TBR. In this study, authors employed the lab-scale TBR, made of 100mm inner diameter acrylic column, packed with particles of two sizes (3, 5 mm) that are used in the actual reactor. Water and air were injected from the top of the column and cross-sectional liquid distribution was captured at the bottom of the column by electrical resistance tomography (ERT). ERT is a tomographic technique that provides the cross-sectional conductivity distribution at the rate of about 50 frames per second by injecting current and measuring voltages between the 16 electrodes that are attached around the column. By analyzing the spatial and temporal characteristics of the liquid distribution obtained by ERT, it was found that particle size has only little impact on induction of pulsating flow and larger particle causes distinct pulses. Smaller particle causes blurred tiny pulses due to higher flow resistance. Larger particle (5 mm) is advantageous for pulsating flow.

Investigation of Liquid Dispersion in the Packed-Bed by Electrical Resistance Tomography

2012 ◽  
Author(s):  
Takeshi Eda ◽  
Achyut Sapkota ◽  
Masahiro Takei
Keyword(s):  
Liquid Flow ◽  
Electrical Resistance ◽  
Packed Bed ◽  
Electrical Resistance Tomography ◽  
Entire Cross Section ◽  
Basic Model ◽  
Liquid Dispersion ◽  
Flow Phenomena ◽  
Radial Dispersion ◽  
Gas Liquid Flow

Revealing gas-liquid permeable flow phenomena in the porous media is helpful for the environmental impact assessment of geological disposal of radioactive waste and purification of radioactive contamination water. This paper aims to investigate the liquid phase dispersion inside co-current downward gas-liquid flow in the bed packed with spherical particle as basic model. Water and air are injected from the top center of column, and water is spreading to the entire cross-section flowing down along the column. Radial dispersion of water is captured by electrical resistance tomography on several axial positions. The results indicated that liquid flow rate have impact on radial dispersion of water.

SIMULATION OF ELECTRODE FOR DUAL-MODALITY ELECTRICAL RESISTANCE TOMOGRAPHY AND ULTRASONIC TRANSMISSION TOMOGRAPHY FOR IMAGING TWO-PHASE LIQUID AND GAS

2015 ◽  
Vol 77 (17) ◽  
Author(s):  
Fazlul Rahman Mohd Yunus ◽  
Ruzairi Abdul Rahim ◽  
Leow Pei Ling ◽  
Nor Muzakkir Nor Ayob ◽  
Yasmin Abdul Wahab ◽  
...  
Keyword(s):  
Liquid Flow ◽  
Electrical Resistance ◽  
Region Of Interest ◽  
Gas Bubble ◽  
3D Numerical Modeling ◽  
Electrical Resistance Tomography ◽  
Two Phase ◽  
Transmission Tomography ◽  
Dual Modality ◽  
Gas Liquid Flow

Accurate multiphase flow measurement of gas/liquid, liquid/solid and liquid/liquid flow is still challenging for researchers in process tomography. The reconstructed images are poor particularly in the center area because of ill-posed inverse problems and limited of measurements data. Dual-modality tomography has been introduced to overcome the problem by means each modality is sensitive to specific properties of materials to be imaged. This paper proposed combination of ultrasonic transmission tomography (UTT) and electrical resistance tomography (ERT) for imaging two phase gas/liquid. In the proposed combination, detection ability in the medium of interest improved because two different images in the same space can be obtained simultaneously. This paper presents 3D numerical modeling approach using COMSOL software for ERT excitation strategy and electrode pre-designed geometry. Electrical resistance tomography (ERT) can be implemented for gas/liquid flow if the liquid is conductive. The objectives of this work is to analyze the optimum electrode dimension and shape in order to improve the situation of: (1) gas bubble detection located in the centre of the medium, (2) potential distribution and current density in a conductive medium, the developed numerical model simulated the changes in resistivity of the conductive material, with variations of electrode sizes, with opposite current excitation implemented into the region of interest. Simulation results show that the electrode size of 12 mm (w) × 40 mm (h) is suitable, which gives a good detection of center gas bubble with diameter 10mm in 100-mm-diameter acrylic vessel. Finally the findings are verified with Image reconstruction using Linear Back Projection (LBP) which gives good indication of the 10mm gas bubble.

scholarly journals Visualisation of flow pattern and measurement of liquid distribution in a random packed column using electrical resistance tomography (ERT)

2021 ◽  
Author(s):  
Nazar Aoda
Keyword(s):  
Flow Pattern ◽  
Flow Rate ◽  
Electrical Resistance ◽  
Packed Column ◽  
Operating Conditions ◽  
Flow Mode ◽  
Electrical Resistance Tomography ◽  
Liquid Distribution ◽  
Flow Rates ◽  
Good Agreement

The aim of this research is to use Electrical Resistance Tomography technique (ERT) to measure factors that affect local mass transfer at various axial locations in a random packed column with diameter 0.3m and bed height 150cm filled with 2 cm plastic spheres. These factors are: liquid maldistribution, velocity profiles, and flow pattern. The system was designed to run in a trickling down-flow mode and a full liquid up-flow mode. Experiments were performed at flow rates of 3, 6, and 9 gpm (or 0.27 x 10⁻², 0.54 x 10⁻² and 0.8 x 10⁻² m³/m² s) and under normal operating conditions of 25C° and atmospheric pressure. The liquid maldistribution factors were measured via ERT technique and the conventional liquid collection method. Both measurements were conducted at various fluid flow rates at different bed heights. The results of ERT were in very good agreement with the conventional method. The standard deviation values were 17% and 21% at flow rates 3 and 6 gpm respectively. The numerical values of velocity for full liquid up flow at 3 gpm were 0.83cm/s, 1.2cm/s, 1.2 cm/s and 1.11 cm/s for different heights of 30, 60 and 90 cm respectively and the numerical values of velocity for trickle down flow at 3 gpm were 16.5 cm/s, 22.5 cm/s and 24 cm/ for different heights of 30, 60 and 90 cm respectively. The values of the liquid maldistribution factor for flow rate 3 gpm were 0.43 (30cm), 0.33(60cm) and 0.30 (90cm) and for flow rate 6 gpm were 0.33(30cm), 0.27(60cm) and 0.22 (90cm). By comparison with findings of many studies conducted on liquid distribution in packed bed column, a good agreement was observed on the relation of Mf and flow rates and bed heights.

scholarly journals Investigation of Multi-Plane Scheme for Compensation of Fringe Effect of Electrical Resistance Tomography Sensor

Sensors ◽  
2019 ◽  
Vol 19 (14) ◽  
pp. 3132 ◽  
Author(s):  
Wenbin Tian ◽  
Xiaofeng Liang ◽  
Xiaolei Qu ◽  
Jiangtao Sun ◽  
Shuo Gao ◽  
...  
Keyword(s):  
Electrical Resistance ◽  
Electrical Resistance Tomography ◽  
Cross Sectional ◽  
Single Plane ◽  
Measurement Plane ◽  
3D Sensing ◽  
Simulation Results ◽  
Multiple Plane ◽  
Fringe Effect ◽  
Plane Scheme

Conventional electrical resistance tomography (ERT) sensors suffer from the fringe effect, i.e., severe distortion of the electric field on both ends of the measurement electrodes, leading to a 3D sensing region for a 2D sensor. As a result, the objects outside an ERT sensor plane affect the sensing and hence image, i.e., deteriorating the image quality. To address this issue, a multiple-plane ERT sensor scheme is proposed in this paper. With this scheme, auxiliary sensor planes are used to provide references for the fringe effect of the measurement plane, for compensation by subtracting the weighed influence of the fringe effect. Simulation results show that the proposed scheme, either three-plane or two-plane sensor, can compensate for the fringe effect induced by objects outside the measurement plane with a variety of axial object distributions, i.e., several non-conductive bars or conductive bars placed at different cross-sectional and axial positions inside the sensor. Experiments were carried out. Images obtained with single-plane and multiple-plane ERT sensors are compared, and the proposed compensation scheme has been hence verified.

scholarly journals Visualisation of flow pattern and measurement of liquid distribution in a random packed column using electrical resistance tomography (ERT)

2021 ◽  
Author(s):  
Nazar Aoda
Keyword(s):  
Flow Pattern ◽  
Flow Rate ◽  
Electrical Resistance ◽  
Packed Column ◽  
Operating Conditions ◽  
Flow Mode ◽  
Electrical Resistance Tomography ◽  
Liquid Distribution ◽  
Flow Rates ◽  
Good Agreement

The aim of this research is to use Electrical Resistance Tomography technique (ERT) to measure factors that affect local mass transfer at various axial locations in a random packed column with diameter 0.3m and bed height 150cm filled with 2 cm plastic spheres. These factors are: liquid maldistribution, velocity profiles, and flow pattern. The system was designed to run in a trickling down-flow mode and a full liquid up-flow mode. Experiments were performed at flow rates of 3, 6, and 9 gpm (or 0.27 x 10⁻², 0.54 x 10⁻² and 0.8 x 10⁻² m³/m² s) and under normal operating conditions of 25C° and atmospheric pressure. The liquid maldistribution factors were measured via ERT technique and the conventional liquid collection method. Both measurements were conducted at various fluid flow rates at different bed heights. The results of ERT were in very good agreement with the conventional method. The standard deviation values were 17% and 21% at flow rates 3 and 6 gpm respectively. The numerical values of velocity for full liquid up flow at 3 gpm were 0.83cm/s, 1.2cm/s, 1.2 cm/s and 1.11 cm/s for different heights of 30, 60 and 90 cm respectively and the numerical values of velocity for trickle down flow at 3 gpm were 16.5 cm/s, 22.5 cm/s and 24 cm/ for different heights of 30, 60 and 90 cm respectively. The values of the liquid maldistribution factor for flow rate 3 gpm were 0.43 (30cm), 0.33(60cm) and 0.30 (90cm) and for flow rate 6 gpm were 0.33(30cm), 0.27(60cm) and 0.22 (90cm). By comparison with findings of many studies conducted on liquid distribution in packed bed column, a good agreement was observed on the relation of Mf and flow rates and bed heights.

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