Mixing time in an agitated multi-lamp cylindrical photoreactor using electrical resistance tomography

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

10.32920/ryerson.14649915.v1 ◽

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

10.32920/ryerson.14645163 ◽

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%.

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Measuring Mixing Time in the Agitation of Non-Newtonian Fluids through Electrical Resistance Tomography

Chemical Engineering & Technology ◽

10.1002/ceat.200800362 ◽

2008 ◽

Vol 31 (12) ◽

pp. 1838-1845 ◽

Cited By ~ 40

Author(s):

L. Pakzad ◽

F. Ein-Mozaffari ◽

P. Chan

Keyword(s):

Electrical Resistance ◽

Mixing Time ◽

Newtonian Fluids ◽

Electrical Resistance Tomography

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

10.32920/ryerson.14645163.v1 ◽

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%.

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