scholarly journals Solid-Liquid Mixing In Agitated Tanks : Experimental And CFD Analysis

2021 ◽  
Author(s):  
Seyed. Hosseini
Keyword(s):  
Suspension Polymerization ◽  
Fluid Dynamic ◽  
Impeller Speed ◽  
Cfd Analysis ◽  
Mixing Performance ◽  
Solid Density ◽  
Liquid Mixing ◽  
Solid Liquid ◽  
Multiple Reference ◽  
Good Agreement

Solid-liquid mixing plays a significant role in crystallization, suspension polymerization, leaching, solid-catalyzed reaction and adsorption. In this study, a computational fluid dynamic (CFD) model was developed for solid-liquid mixing in a cylindrical tank equipped with a top-entering impeller. The multiple reference frame (MRF) technique, k-ε model and Eulerian-Eulerian approach were employed to simulate the impeller rotation, turbulent flow and multiphase flow, respectively. The effects of impeller speed, solid concentration, particle size, solid density and impeller clearance on the mixing performance of four different impellers (A310, marine propeller, pitched blad turbine and A320) were investigated. The CFD results were in good agreement with experimental data measured using electrical resistance tomography (ERT). In order to investigate the mixing quality in this study, the impeller speed required for maximum homogeneity, clouding height, and just-suspended impeller speed were investigated.

scholarly journals Solid-Liquid Mixing In Agitated Tanks : Experimental And CFD Analysis

2021 ◽  
Author(s):  
Seyed. Hosseini
Keyword(s):  
Suspension Polymerization ◽  
Fluid Dynamic ◽  
Impeller Speed ◽  
Cfd Analysis ◽  
Mixing Performance ◽  
Solid Density ◽  
Liquid Mixing ◽  
Solid Liquid ◽  
Multiple Reference ◽  
Good Agreement

Solid-liquid mixing plays a significant role in crystallization, suspension polymerization, leaching, solid-catalyzed reaction and adsorption. In this study, a computational fluid dynamic (CFD) model was developed for solid-liquid mixing in a cylindrical tank equipped with a top-entering impeller. The multiple reference frame (MRF) technique, k-ε model and Eulerian-Eulerian approach were employed to simulate the impeller rotation, turbulent flow and multiphase flow, respectively. The effects of impeller speed, solid concentration, particle size, solid density and impeller clearance on the mixing performance of four different impellers (A310, marine propeller, pitched blad turbine and A320) were investigated. The CFD results were in good agreement with experimental data measured using electrical resistance tomography (ERT). In order to investigate the mixing quality in this study, the impeller speed required for maximum homogeneity, clouding height, and just-suspended impeller speed were investigated.

scholarly journals Using electrical resistance tomography to characterize and optimize the mixing of micron sized polymeric particles in a slurry reactor

2021 ◽  
Author(s):  
Parisa Tahvildarian
Keyword(s):  
Electrical Resistance ◽  
Tap Water ◽  
Slurry Reactor ◽  
Operating Conditions ◽  
Impeller Speed ◽  
Design Parameters ◽  
Electrical Resistance Tomography ◽  
Latex Particles ◽  
Liquid Mixing ◽  
Solid Liquid

A solid-liquid mixing system has a significant role in the suspension polymerization, crystallization, adsorption, and solid-catalyzed reactions. In this study, Electrical Resistance Tomography (ERT) was employed to investigate the effect of the particle size, the design parameters such as impeller type, impeller clearance and impeller diameter as well as operating conditions such as impeller speed, impeller pumping mode, and solids concentration on the mixing of micron sized latex particles in a slurry reactor. The ERT data were used to calculate the concentration profile and the degree of homogeneity in three dimensions, as a function of design parameters and operating within the reactor. In this work, tap water and latex particles (5.2 µm, 8.5 µm, 9.1 µm) were used as liquid and solid phase, respectively. Six axial impellers were utilized (A310, A100, A200, A320, A315, 3AM) with impeller speed (N) varying from 252 rpm to 400 rpm. Impeller diameter to tank diameter ratios (D/T) were in the range of 0.29 to 0.47 while, the impeller clearance (C/T) was changed in the range of T/3.8 to T/2.5. Impeller pumping was tested in both downward and upward directions. The concentration of latex particles was ranged between 15 wt% and 30 wt%. This study shows that the level of homogeneity in a solid-liquid mixing system improved with the increase in impeller speed. However, after achieving the maximum level of homogeneity, any further rise in the impeller speed had a detrimental effect on the level of homogeneity. A310 impeller, wtih D/T ratio of 0.31, demonstrated the highest level of homogeneity while the upward pumping direction was found to be more efficient than the downward one. In addition, a clearance of T/3 proved to create the highest level of homogeneity. Also, the results showed that a rise in the size and concentration of particles decreases the level of homogeneity. Thus, 5.2 µm latex particles with the concentration of 15 wt% demonstrated the highest level of homogeneity. Applying the findings of this study will lead to improved equipment design, chemical cost reduction, increased production rate, improved quality of products, and more efficient use of power in slurry reactors.

scholarly journals Numerical analysis and optimization of key parts in the stirred tank based on solid-liquid flow field

2022 ◽  
Vol 105 (1) ◽  
pp. 003685042110672
Author(s):  
Hongwan Jiang ◽  
Sen Yuan ◽  
Hao Liu ◽  
Weiwei Li ◽  
Xiaorong Zhou
Keyword(s):  
Flow Field ◽  
Particle Concentration ◽  
Flow Model ◽  
Particle Distribution ◽  
Dead Zone ◽  
Clear Liquid ◽  
Mixing Performance ◽  
Liquid Suspension ◽  
Solid Liquid ◽  
Multiple Reference

In order to further improve the mixing performance of the mixing device, the structure of the agitator was optimized, and the effects of the diameter and pitch of the agitator on the solid-liquid suspension characteristics were analyzed by single factor method. Multiple reference frame (MRF), computational fluid dynamics, Euler multiphase flow model and standard K- ε turbulence model were used to investigate the effect of the height from the bottom of the agitator on the suspension characteristics of particles in the agitator was studied. The results show that reducing the height from the bottom of the agitator can promote the suspension of particles at the bottom of the tank, but too low height from the bottom will easily produce mixing dead zone at the bottom of the tank, and cause the accumulation of particles. Reducing the height of the agitator from the bottom will enlarge the clear liquid area of the flow field, cause uneven particle distribution and increase the stirring torque. With the increase of agitator diameter, the critical suspension speed of the flow field decrease, but the stirring power required by the flow field increase. Increasing the blade spacing in a certain range can promote the suspension of particles and make the distribution of particles in the flow field more uniform. Therefore, the mixing power and the uniformity of particle concentration distribution need to be considered together in order to make the mixing device more efficient and energy-saving.

scholarly journals Using electrical resistance tomography to characterize and optimize the mixing of micron sized polymeric particles in a slurry reactor

2021 ◽  
Author(s):  
Parisa Tahvildarian
Keyword(s):  
Electrical Resistance ◽  
Tap Water ◽  
Slurry Reactor ◽  
Operating Conditions ◽  
Impeller Speed ◽  
Design Parameters ◽  
Electrical Resistance Tomography ◽  
Latex Particles ◽  
Liquid Mixing ◽  
Solid Liquid

A solid-liquid mixing system has a significant role in the suspension polymerization, crystallization, adsorption, and solid-catalyzed reactions. In this study, Electrical Resistance Tomography (ERT) was employed to investigate the effect of the particle size, the design parameters such as impeller type, impeller clearance and impeller diameter as well as operating conditions such as impeller speed, impeller pumping mode, and solids concentration on the mixing of micron sized latex particles in a slurry reactor. The ERT data were used to calculate the concentration profile and the degree of homogeneity in three dimensions, as a function of design parameters and operating within the reactor. In this work, tap water and latex particles (5.2 µm, 8.5 µm, 9.1 µm) were used as liquid and solid phase, respectively. Six axial impellers were utilized (A310, A100, A200, A320, A315, 3AM) with impeller speed (N) varying from 252 rpm to 400 rpm. Impeller diameter to tank diameter ratios (D/T) were in the range of 0.29 to 0.47 while, the impeller clearance (C/T) was changed in the range of T/3.8 to T/2.5. Impeller pumping was tested in both downward and upward directions. The concentration of latex particles was ranged between 15 wt% and 30 wt%. This study shows that the level of homogeneity in a solid-liquid mixing system improved with the increase in impeller speed. However, after achieving the maximum level of homogeneity, any further rise in the impeller speed had a detrimental effect on the level of homogeneity. A310 impeller, wtih D/T ratio of 0.31, demonstrated the highest level of homogeneity while the upward pumping direction was found to be more efficient than the downward one. In addition, a clearance of T/3 proved to create the highest level of homogeneity. Also, the results showed that a rise in the size and concentration of particles decreases the level of homogeneity. Thus, 5.2 µm latex particles with the concentration of 15 wt% demonstrated the highest level of homogeneity. Applying the findings of this study will lead to improved equipment design, chemical cost reduction, increased production rate, improved quality of products, and more efficient use of power in slurry reactors.

scholarly journals Analysis of Radial Inflow Turbine Losses Operating with Supercritical Carbon Dioxide

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3561
Author(s):  
Antti Uusitalo ◽  
Aki Grönman
Keyword(s):  
Fluid Dynamic ◽  
Dynamic Simulations ◽  
Average Deviation ◽  
Loss Analysis ◽  
Specific Speed ◽  
Loss Models ◽  
Rotor Losses ◽  
Radial Turbines ◽  
Design Power ◽  
Good Agreement

The losses of supercritical CO2 radial turbines with design power scales of about 1 MW were investigated by using computational fluid dynamic simulations. The simulation results were compared with loss predictions from enthalpy loss correlations. The aim of the study was to investigate how the expansion losses are divided between the stator and rotor as well as to compare the loss predictions obtained with the different methods for turbine designs with varying specific speeds. It was observed that a reasonably good agreement between the 1D loss correlations and computational fluid dynamics results can be obtained by using a suitable set of loss correlations. The use of different passage loss models led to high deviations in the predicted rotor losses, especially with turbine designs having the highest or lowest specific speeds. The best agreement in respect to CFD results with the average deviation of less than 10% was found when using the CETI passage loss model. In addition, the other investigated passage loss models provided relatively good agreement for some of the analyzed turbine designs, but the deviations were higher when considering the full specific speed range that was investigated. The stator loss analysis revealed that despite some differences in the predicted losses between the methods, a similar trend in the development of the losses was observed as the turbine specific speed was changed.

scholarly journals Numerical study of hydrogen mild combustion

2009 ◽  
Vol 13 (3) ◽  
pp. 59-67 ◽  
Author(s):  
Enrico Mollica ◽  
Eugenio Giacomazzi ◽  
Marco di
Keyword(s):  
Numerical Study ◽  
Fluid Dynamic ◽  
Thermal Gradients ◽  
Radiation Model ◽  
Dynamic Simulations ◽  
Mild Combustion ◽  
Preheating Temperature ◽  
Nitric Oxide Emissions ◽  
Gas Recirculation ◽  
Good Agreement

In this article a combustor burning hydrogen and air in mild regime is numerically studied by means of computational fluid dynamic simulations. All the numerical results show a good agreement with experimental data. It is seen that the flow configuration is characterized by strong exhaust gas recirculation with high air preheating temperature. As a consequence, the reaction zone is found to be characteristically broad and the temperature and concentrations fields are sufficiently homogeneous and uniform, leading to a strong abatement of nitric oxide emissions. It is also observed that the reduction of thermal gradients is achieved mainly through the extension of combustion in the whole volume of the combustion chamber, so that a flame front no longer exists ('flameless oxidation'). The effect of preheating, further dilution provided by inner recirculation and of radiation model for the present hydrogen/air mild burner are analyzed.

Flow Channelization Method to Enhance Transformer Radiator Cooling Capacity

2018 ◽  
Vol 10 (6) ◽  
Author(s):  
Subhashish Dasgupta ◽  
Anurag Nandwana ◽  
K. Ravikumar
Keyword(s):  
Natural Convection ◽  
Heat Exchangers ◽  
Fluid Dynamic ◽  
Cost Effective ◽  
Cooling Capacity ◽  
Structural Features ◽  
Cfd Analysis ◽  
Cooling Process ◽  
Effective Technology ◽  
Convection Cooling

Abstract Most oil-cooled equipment like transformers are provided with radiators or heat exchangers, for the heated oil to exchange heat with the surrounding air by natural convection cooling, assisting the overall cooling process. While such radiators are effective accessories in controlling equipment temperature rise, it is ever desirable to further enhance the cooling capacity by design modifications or incorporating simplistic and cost-effective cooling technologies. In this study, computational fluid dynamic (CFD) analysis has been performed to evaluate the possibility of improving radiator performance by flow channelizing structures. Significant benefits (up to 17% increase in heat transfer coefficient) of imposing such structures, like a top chimney and an enclosure surrounding the radiator, were obtained. Although several past studies have confirmed that natural convection cooling effect can be intensified by flow channelization, the phenomenon is unique to a particular application. Given the wide variety in applications, in terms of shape, size, and structural features, it is necessary to study the effect in a given application of interest. This study points to a new direction in enhancing the cooling capacity of transformer radiators, inducing flow channelization, an easy-to-implement and cost-effective technology. Further, the study offers interesting learnings regarding flow channelization effects, which are invaluable guidelines for designers of future radiators.

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