scholarly journals Using electrical resistance tomography (ERT) and computational fluid dynamics (CFD) to study the mixing of pseudoplastic fluids with a SCABA 6SRGT impeller

2021 ◽  
Author(s):  
Leila Pakzad
Keyword(s):  
Flow Field ◽  
Flow Pattern ◽  
Electrical Resistance ◽  
Mixing Time ◽  
Three Dimensions ◽  
Cfd Modeling ◽  
Cube Root ◽  
Mixing Times ◽  
Electrical Resistance Tomography ◽  
Good Agreement

The objective of this work is to use electrical resistance tomography (ERT) and computational fluid dynamic (CFD) modeling to investigate the flow field generated by a Scaba 6SRGT impeller in the agitation of the xanthan solution, as a pseudoplastic fluid with yield stress. ERT provides a non-destructive technique to measure, in three dimensions, the concentration fields inside the mixing tanks. Using ERT, the impeller flow pattern, the dimensions of the cavern formed and the mixing time in the agitation of xanthan solutions were evaluated. The sizes of cavern measured using ERT were in good agreement with that calculated using Elson's model (cylindrical model). ERT provides both overall mixing time using 1264 probes (316 probes for each plan) and local mixing time using 4 selected probes or pixels. The dimensionless mixing times obtained from ERT were correlated well with the Moo-Young correlation, confirming that increased impeller speeds decreases the mixing times. The 3D flow field generated by a Scaba 6SRGT impeller and tracer homogenization in the agitation of xanthan gum were also simulated using the commercial CFD package (FLUENT). The experimental torque measurements were used to validate the numerical simulations. The validated CFD model provided useful information regarding the impeller pumping capacity and flow pattern, the velocity profiles, the formation of cavern around the impeller, and the mixing time. CFD results show good qualitative as well as quantitative agreement with the experimental results and theory. The sizes of cavern measure using CFD were in good agreement with that calculated using Elson's model. The local mixing times predicted from CFD simulations agreed well with literature in a way that mixing times varied inversely with the cube root of the power consumed per unit volume of the solution. CFD under predicted the local mixing times measured using ERT by 11-47%.

scholarly journals Using electrical resistance tomography (ERT) and computational fluid dynamics (CFD) to study the mixing of pseudoplastic fluids with a SCABA 6SRGT impeller

2021 ◽  
Author(s):  
Leila Pakzad
Keyword(s):  
Flow Field ◽  
Flow Pattern ◽  
Electrical Resistance ◽  
Mixing Time ◽  
Three Dimensions ◽  
Cfd Modeling ◽  
Cube Root ◽  
Mixing Times ◽  
Electrical Resistance Tomography ◽  
Good Agreement

The objective of this work is to use electrical resistance tomography (ERT) and computational fluid dynamic (CFD) modeling to investigate the flow field generated by a Scaba 6SRGT impeller in the agitation of the xanthan solution, as a pseudoplastic fluid with yield stress. ERT provides a non-destructive technique to measure, in three dimensions, the concentration fields inside the mixing tanks. Using ERT, the impeller flow pattern, the dimensions of the cavern formed and the mixing time in the agitation of xanthan solutions were evaluated. The sizes of cavern measured using ERT were in good agreement with that calculated using Elson's model (cylindrical model). ERT provides both overall mixing time using 1264 probes (316 probes for each plan) and local mixing time using 4 selected probes or pixels. The dimensionless mixing times obtained from ERT were correlated well with the Moo-Young correlation, confirming that increased impeller speeds decreases the mixing times. The 3D flow field generated by a Scaba 6SRGT impeller and tracer homogenization in the agitation of xanthan gum were also simulated using the commercial CFD package (FLUENT). The experimental torque measurements were used to validate the numerical simulations. The validated CFD model provided useful information regarding the impeller pumping capacity and flow pattern, the velocity profiles, the formation of cavern around the impeller, and the mixing time. CFD results show good qualitative as well as quantitative agreement with the experimental results and theory. The sizes of cavern measure using CFD were in good agreement with that calculated using Elson's model. The local mixing times predicted from CFD simulations agreed well with literature in a way that mixing times varied inversely with the cube root of the power consumed per unit volume of the solution. CFD under predicted the local mixing times measured using ERT by 11-47%.

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 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 Electrical Resistance Tomography for Assessing Water Movement in Cracked Cementitious Mixtures

2018 ◽  
Vol 199 ◽  
pp. 11016
Author(s):  
Keiyu Kawaai ◽  
Isao Ujike
Keyword(s):  
Electrical Resistance ◽  
Water Movement ◽  
Gradual Increase ◽  
Concrete Specimen ◽  
Electrical Measurements ◽  
Electrical Resistance Tomography ◽  
Water Ingress ◽  
Elapsed Time ◽  
Flow Through ◽  
Good Agreement

Electrical resistance tomography (ERT) has been studied for visualizing variations of conductivity in concrete specimens. In recent years, unsaturated water flow through pores formed in concrete has been intensively examined though ERT systems to visualize the permeation front that gradually changes with elapsed time. This study examines water movement through internal cracks which are typically not observed on the surface of mortar or concrete specimens via ERT systems. The results indicate the gradual increase of saturated region owing to the ingress of water through cracked surface up to 120 hours. And, the region with higher conductivity estimated in uncracked parts is evidently in good agreement with higher moisture content measured by moisture meter on the split surface. In addition, the presence of crack in concrete specimen subjected to water ingress is clearly visualized via ERT images owing to rapid water movement in cracked zones. This study has provided the important insight that the ingress and the movement of water through pores and cracks formed in cementitious mixtures could be assessed via electrical measurements.

scholarly journals Mixing time study in agitated multiple-lamp UV photoreactor using electrical resistance tomography

2021 ◽  
Author(s):  
Zhen Fang Zhao
Keyword(s):  
Electrical Resistance ◽  
Uv Light ◽  
Mixing Time ◽  
Water Disinfection ◽  
Electrical Resistance Tomography ◽  
Rushton Turbine ◽  
Disinfection Process ◽  
Impeller Type ◽  
Uv Lamps ◽  
The Impact

The present study is devoted to the mixing time investigation in a single stirrer UV photoreactor aiming at the drinking water disinfection process. Electrical resistance tomography (ERT) was employed to measure the mixing quality due to the significant advantages. The reactor was a flat-bottomed cylindrical tank with a diameter of 38.1 cm and a height of 60.1 cm fitted with four symmetrically located vertical baffles. The performaces of a 6-blade Rushton turbine and a 4-blade 45° pitched-blade turbine were explored in this study. In the absence of the UV light, four PVC rods were used to replace four UV lamps and evaluate the impact of the locations of the UV tubes on the mixing time. The experimental results demonstrated the feasibility of the ERT system to monitor the mixing process in the UV photoreactor. The ERT results also indicated that the locations of the UV tubes had a signigicant impact on the mixing performance in such a batch stirred tank reactor. Other parameters encompassing the impeller rotational speed the impeller type, and off-bottom clearance were presented with respect to the extensive effects on the mixing time and power consumption.

scholarly journals Mixing time study in agitated multiple-lamp UV photoreactor using electrical resistance tomography

2021 ◽  
Author(s):  
Zhen Fang Zhao
Keyword(s):  
Electrical Resistance ◽  
Uv Light ◽  
Mixing Time ◽  
Water Disinfection ◽  
Electrical Resistance Tomography ◽  
Rushton Turbine ◽  
Disinfection Process ◽  
Impeller Type ◽  
Uv Lamps ◽  
The Impact

The present study is devoted to the mixing time investigation in a single stirrer UV photoreactor aiming at the drinking water disinfection process. Electrical resistance tomography (ERT) was employed to measure the mixing quality due to the significant advantages. The reactor was a flat-bottomed cylindrical tank with a diameter of 38.1 cm and a height of 60.1 cm fitted with four symmetrically located vertical baffles. The performaces of a 6-blade Rushton turbine and a 4-blade 45° pitched-blade turbine were explored in this study. In the absence of the UV light, four PVC rods were used to replace four UV lamps and evaluate the impact of the locations of the UV tubes on the mixing time. The experimental results demonstrated the feasibility of the ERT system to monitor the mixing process in the UV photoreactor. The ERT results also indicated that the locations of the UV tubes had a signigicant impact on the mixing performance in such a batch stirred tank reactor. Other parameters encompassing the impeller rotational speed the impeller type, and off-bottom clearance were presented with respect to the extensive effects on the mixing time and power consumption.

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