Project Report.docx

A Project Stage-I Report on

Design & Fabrication of a portable mixer for low viscosity fluids By Mr. Mohtasim M. A Mapkar

Mr. Prasad A More

Mr. Abuzar Madki

Mr. Parth S Kulkarni

Guide: Mr. P.M. Sonawane

Department Of Mechanical Engineering Sinhgad Academy Of Engineering, Kondhwa [2018-19] Sinhgad Technical Education Society’s

Sinhgad Academy of Engineering, Kondhwa (Bk), Pune

CERTIFICATE This is to certify that “GROUP NO: 1.” has successfully completed the Project review 1 work entitled “Design and fabrication of portable industrial mixer for low viscosity fluids” under my supervision, in the partial fulfillment of Bachelor of Engineering - Mechanical Engineering, by University of Pune.

Date: 29/08/2018

Place: Pune

Guide‘s Name: P. M Sonawane

Head of Department: S.C. Shilwant

Project Coordinator: M.R. Rampure

Principal: K.P Patil

CONTENTS

1. INTRODUCTION

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2. LITERATURE SURVEY

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3. OBJECTIVES

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4. METHODOLOGY

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5. DESIGN

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6. EXPECTED OUTCOME

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7. REFERENCES

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Chapter 1 INTRODUCTION Mixing equipment must be designed for mechanical and process operation. Although mixer design begins with a focus on process requirements, the mechanical design is essential for successful operation. Usually, a competent manufacturer of mixing equipment will take responsibility for the mechanical design. However, process conditions, such as impeller operation near a liquid surface, can impose severe mechanical loads. Similarly, the process environment will influence the selection of a motor enclosure. In many ways the process requirements can have a direct impact on the mechanical design. In other ways, such as the natural frequency of a mixer shaft, appropriate mechanical design must be determined by the equipment designer.

Because of the diversity of fluid mixing applications and variety of vessels, many different styles of mixers are used in industrial applications. Mixer sizes include small fractionalhorsepower portable mixers to huge 1000 HP plus mixers. Although normally viewed as a single piece of equipment, like a pump, the typical mixer is composed of several individual components, such as a motor, gear reducer, seal, shaft, impellers, and tank, which is often designed and purchased separately. Although highly customized for many applications, most mixers are a combination of standard components, sometimes with modifications, and often with unique characteristics, such as shaft length.

Generalizations, especially for mixers, can misrepresent individual situations, but some features are common to the largest number of mixers built worldwide. The most common motive force for a mixer is an electric motor, so a knowledge of standard motor characteristics is useful. Most mixers operate at or below typical motor speeds, so some type of speed reduction is common. Speed reduction can be accomplished with several

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different types of gears, usually in enclosed housings, or with belts and sheaves. Besides speed reduction, antifriction bearings are found in all types of rotating equipment. Some type of seal around the rotating shaft is required for closed-tank operation and the type depends on degree of seal required, operating pressure, and operating temperature. The shaft for a mixer, especially a large one, involves significant mechanical design, partly because of the myriad of shaft lengths, impeller sizes, and operating speeds, and partly because both strength and rigidity are necessary for a successful design. The combination of custom process and mechanical design necessary for mixers is unique for chemical process equipment. Mechanical design does not end with the shaft, since strength and practical issues remain for the impeller.

Another part of mixer design is the tank in which the mixer is used, since tank dimensions influence mixer features, especially shaft length. Conversely, a mixer requires tank features, such as baffles, support strength, and other tank internals. Materials of construction, although most commonly metal alloys for mixers, depend on process chemistry and operational requirements. Even with the diversity of mixing equipment, features such as motors and materials of construction are mechanical considerations, common to all types of mixers. Fluid mixer design is often thought of as the application of two engineering disciplines in sequence. The first step is process design from chemical perspective and involves specification of impeller configuration, speed, temperature, and pressure, etc. The basic need in the step is to make sure the installed unit operation performs the necessary process tasks. Common process specifications are: 

Mild blending of miscible fluids

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High viscosity blending

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Solid suspension or dissolution

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Liquid-liquid dispersion and/or mass transfer

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Gas-liquid mass transfer

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Heat transfer

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The second step in design sequence is mechanical design of mixer components. The fundamental approach is straightforward, design for power (torque and speed), then shaft loads, and finally mixer dynamics. For larger systems above 100 HP it may be prudent to perform a mixer system modal analysis (FEA) to avoid unexpected interactions. General test procedure and design methodology are based on the assumption that the loading on the mixer and vessel components are geometrically symmetric and temporally invariant- a condition that is not often met.

The design of mixer consists of a prime mover, gear reduction unit, a shaft and impellers. Most of the installations have overhung shafts, i.e. without a steady bearing to support the free end of shaft. Fig 1 illustrates the forces on impeller and shaft configuration. The main forces are torque, bending loads, and thrust. The other major analysis in the design is vibration characteristic of mixer, especially the shaft since system harmonics can lead to amplification of any of the major forces. In practical mixer design, the main critical components are usually bending loads on shaft and blades and system vibration characteristics.

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Chapter 2 LITERATURE SURVEY 2.1. Literature Survey [1] Impeller design for mixing of suspensions by Tomas Jirout, Frantisek Rieger Tomas Jirout, Frantisek Rieger studied the effect of impeller type on off-bottom particle suspension. The important parameters for designing of mixing apparatuses for suspension, critical impeller speed and power consumption are necessary for suspension of solid particles. On the basis of numerous suspension measurements, correlations were proposed for calculation concentrations and particle diameters. The suspension efficiency of tested impellers was compared by means of power consumption required for off-bottom suspension of solid particles. All measurements were carried out in transparent cylindrical vessels with dished bottom. The vessels were equipped with four radial baffles of width b = 0.1·D. The height of the liquid level was equal to the vessel diameter H = D. All measurements took place under the turbulent regime and results were evaluated in the form of dimensionless suspension and power characteristics. The primary experimental data obtained were transformed into dimensionless criteria and plotted as suspension characteristics. Suspension characteristics for the turbulent region are dependencies of modified Froude number Fr´ on the dimensionless particle size dp/D at constant volumetric particle concentration cv. The pitched three-blade turbine with diagonally folded blades has the lowest values of justsuspended impeller speed in the whole measured range of dimensionless particle diameter dp/D and the volumetric concentration of solid phase cv. The values of just-suspended impeller speed are practically the same for other used impellers in lower particle volumetric concentrations. However, the cylindrical three-blade turbine has the highest values of critical impeller speed for higher concentrations of solid phase. The suspension efficiency of impellers used in experiments is compared by means of dimensionless power consumption necessary for off-bottom particle suspension. The pitched three-blade turbine with diagonally folded blades requires lower power consumption for suspension than the pitched three-blade turbine and the pitched cylindrical three-blade turbine. The standard pitched three-blade turbine has the highest energetic requirements for off-bottom particle suspension. This is valid for the whole measured range of the dimensionless particle diameter dp/D and the volumetric concentration of solid phase cv.

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From the paper it is concluded that one of the very important parameters for designing of mixing apparatuses for suspensions are the critical (just-suspended) impeller speed and power consumption necessary for off-bottom suspension of solid particles. On the basis of numerous suspension measurements there were proposed correlations for calculation of just-suspended impeller speed of eleven impeller types and geometries in the wide range of concentrations and particle diameters. The following conclusions might be drawn from comparison of the suspension efficiency by means of the dimensionless power consumption necessary for off-bottom suspension of solid particles: • Hydrofoil impellers have higher suspension efficiency than the standard 45° pitchedblade impellers. • All hydrofoil impellers have roughly the same suspension efficiency when compared at optimum impeller clearance. • Propellers are more sensitive on impeller clearance than the other impellers in investigated range. • Geometrical simplicity of the pitched three-blade turbine with diagonally folded blades according to Czech standard CVS 69 1043 at the comparable suspension efficiency with the other hydrofoil impellers makes this impeller the most favorable one. • Dimensionless power consumption necessary for particle suspension is practically independent of the blade number of pitched blade turbine with diagonally folded blades. • Pitch blade angle has minimum effect on the suspension efficiency in region of the relatively fine particles. The pitched three-blade turbine with blade angle α = 45° has the highest energetic requirement for suspension among the compared pitched blade impellers in the region of relatively large particles.

[2] Potential of an asymmetrical agitation in industrial mixing by Kazuhiko Nishi, Naoki Enya Kazuhiko Nishi, Naoki Enya studied the performance of an eccentrically located MAXBLEND impeller was investigating, based on the power consumption. Further, the torque and horizontal load on the agitating shaft in an eccentric mixer with a MAXBLEND impeller were measured in turbulent state. In comparison with the laminar flow the Np of the eccentric mixing and concentric mixing in small. However in the turbulent region (Re > 2000), the Np of the eccentric mixing is larger than concentric mixing without baffles. It was confirmed that the large amount of energy can be supplied to the mixing liquid in eccentric mixing. Eccentric mixing under suitable conditions controlled the flow pattern in the vessel in good mixing than concentric mixer. Since these impellers have a high mixing performance over a wide range of viscosities, they are used in mixing, dispersion, reaction and polymerization processes. Their use in the food and pharmaceutical industries is being considered. For agitation in the turbulent region, these large impellers are usually used with baffles to promote mixing. However,

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baffles often cause problems for washing and sterilization. Furthermore, in the laminar region, baffles are not effective for mixing, and in fact, they often obstruct mixing. Eccentric mixing is one of the traditional methods of promoting mixing in a vessel without baffles. An eccentrically located impeller generates a vertical flow, which contributes to mixing, without baffles. If a large impeller is used at an eccentric position, it is expected that the high performance of the large impeller can be combined with the advantages of an eccentric mixer. In this study, a MAXBLEND impeller was investigated as an example of a large impeller. The power consumption and mixing time of a MAXBLEND impeller were measured under various eccentric conditions. Furthermore, the mixing performance based on the power consumption of eccentric mixing with a MAXBLEND impeller was investigated. When eccentric mixing is used industrially, we should be concerned about the horizontal load to a agitating shaft. It is expected that the average torque and horizontal load on agitating shaft are larger than in the concentric mixing without baffles. Since these values fluctuate with the rotation of the impeller, the instantaneous maximum value is still larger. The large, fluctuating torque and horizontal load can cause serious problems, such as the falling off of the impeller or the breakage of the shaft, motor, mechanical seal or gearbox. It is, therefore, important to understand the relation between these values and the impeller rotational speed when designing the mixing equipment and determining the operating conditions. In this study, the torque and horizontal load were measured in eccentric mixing using a MAXBLEND impeller, as an example of a large impeller, at various impeller rotational speeds and under various eccentric conditions in a turbulent state. Power consumption of the impeller was measured with a torque meter (Satake Chemical Equipment Mfg Ltd.; ST-3000). This equipment can measure the torque on the agitating shaft in the mixing liquid without mechanical friction by correcting, using the torque value previously measured in air. Mixing time was measured by a decolorization method using iodine and sodium thiosulfate. The mixing liquid in the vessel was colored by adding 0.010 L of the 0.5 mol/L iodine solution (8.0 × 10−4 mol/L), and mixing with a sufficiently large impeller rotational speed. The 0.012 L of 1.0 mol/L sodium thiosulfate solution (1.2 chemical equivalent to iodine) was injected, and decolorization started. In eccentric mixing, the sodium thiosulfate solution was injected at a point midway between the shaft and the vessel wall, on the side opposite to the eccentric direction. Mixing time, was determined based on a video image. Water and glycerol, at fixed concentrations, were used as the mixing liquids. The power consumption in neat glycerol was proportional to the square of the impeller rotational speed. It was presumed that the flow state was laminar. The change in power consumption with the eccentric length was small. The power consumption at LE = 0.04 m was slightly larger than that of concentric mixing with baffles. The power consumption in water was smaller than that in glycerol, and it was proportional to the cube of the impeller rotational speed. This indicates that flow was in a turbulent state. When the eccentric length increased, the power consumption increased. The power consumption at LE=0.04 m was almost the same as that of baffled mixing. The mixing time was considered a non-dimensional quantity, given by πM. The relation

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between πM and Re . In the region where Re < 2000, when Re increased, πM decreased. In this region, which was considered to be in a laminar or a transition state, the value of πM of eccentric mixing was smaller than that of concentric mixing with and without baffles. The eccentric impeller generated asymmetrical flow, which promoted mixing. On the other hand, in the region where Re > 2000, the value of πM was almost constant for each value of LE. This was characteristic of a turbulent state. In this region, the value of πM of eccentric mixing was clearly smaller than that of concentric mixing without baffles. Turbulent diffusion dominated πM during mixing in a turbulent state. It was predicted that the turbulence intensity of eccentric mixing would be lower than that of concentric mixing with baffles. The average of torque was proportional to the square of the impeller rotational speed, and increased exponentially to 4.6 times the eccentric ratio. When the eccentric ratio was small, the torque fluctuated due to the influence of the flow. However, when the eccentric ratio was large, the influence of the mechanical load, such as the approach of the blade to the vessel wall, generated fluctuation. Therefore, the torque fluctuated at twice the frequency of the impeller rotational speed. The standard deviation of the torque, which corresponds to the amplitude of fluctuation, was smaller than the average torque. The equation for the estimation of the torque from the impeller rotational speed and the eccentric ratio was proposed. The horizontal load was almost zero. The load in the y-direction was one order larger than that in the x direction. The horizontal load fluctuated at the same frequency as the impeller rotational speed. From this result, it was considered probable that the mechanical effect was dominant in generating the fluctuation in the horizontal load. The y-direction load and the resultant load in the x- and y-directions were proportional to the power of the impeller rotational speed and were an exponential function of the eccentric ratio. Based on this relation, equations for estimating the horizontal load were proposed. The eccentric impeller generated asymmetrical flow, which promoted mixing. Eccentric mixing under suitable conditions controlled the flow pattern in the vessel and resulted in good mixing.

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[3] Design analysis and scale up of mixing processes by H.S Pordal and C.J Matice H.S. Pordal and C. J. Matice studied on multi-tiered approach for the design analysis and scale up of mixing processes. The primary function of a mixing vessel is to provide adequate stirring and mixing of the fluid. The mixing characteristics influence the product quality and efficiency of the process to a great degree. Stirred vessels come in various shapes and sizes. The main vessel is cylindrical in shape and the vessel bottom is very often contoured. Baffles are included in the vessel to break the vortex and prevent solid body rotation of the fluid. Draft tubes are included to direct suction and discharge streams. Diptubes are employed to inject fluids at specific locations. An important component of a stirred tank is the impeller. The rotating impeller imparts motion and shear to the fluid thus inducing mixing. The type of impeller employed depends on the nature of the task. Very often the same stirred vessel is required to perform various duties. It is important to ensure efficient and optimum operation of the stirred vessel for a given duty. There is also need to create process conditions that are optimum at the lab-scale, pilot-scale and production-scale so that productivity is maximized. Tier-one methods are based on general guide-lines and dimensional analysis for mixing equipment. Vendor recommendations and equipment sizing based on rules-of-thumb fall in this category. Tier-two solution methods employ analytical techniques to solve mixing problems. These methods utilize empirical data along with solutions of mass and momentum on global scale. In this approach, fundamental equations of fluid dynamics are simplified based on experimental results and solved to provide rapid analysis of stirred vessels. These tools are valuable in identification of good and bad blending practices and estimation of average mixing characteristics. For a selected stirred vessel configuration, tier-two methods can be applied to estimate important mixing parameters such as average tangential velocity distribution, power, average axial velocity distribution, mixing time, overall energy dissipation rate and turbulence. These parameters can be computed at the lab-scale, pilotscale or production-scale for process scale-up or scale-down. The impact of configuration changes on stirred vessel performance can be rapidly estimated. Visimix from Visimix Ltd. is an analysis tool based on tier-two methods. Visimix captures years of experience and wealth of information from various sources. Mixing vessel configuration parameters such as tank shape, size, impeller type and size can be easily defined using the user interface to Visimix. The effect of various process parameters such as fill level, impeller rpm can be rapidly assessed. This tool can be applied to rapidly assess the impact of mixing vessel configuration, fluid properties and .process parameters on mixing performance. Key mixing performance parameters are .readily available in Visimix for design evaluation decisions. In the current study. Vismix .is applied to solve a number of mixing problems.

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Tier-three methods involve detailed measurements and predictions. Experimental .measurements and analytical methods based on Computational Fluid Dynamics (CFD) .are classified as tier-three methods. CFD methods are based on the solution of Navier .Stokes equations to predict stirred vessel behavior. These methods are useful in evaluating detailed flow patterns in complex geometries and in situations where tier-two .methods are not applicable. CFD methods are based on the solution of conservation .equations of mass, momentum and energy at thousands of locations within the flow .domain. A CFD solution provides full-field data; flow variables at each and every .location in the domain are available: a graphical representation of the flow can be created. Solution can be verified by evaluating the problem by tier two and tier three methods and then the results of the two are compared to obtain the optimum solution. Stirred Vessel Configuration Selection: In this study, general guidelines based on tier .one methods are initially applied to obtain overall scale of a mixing vessel. The mixing characteristics for various impeller types are evaluated based on tier-two methods using Visimix. Table-I depicts performance of stirred vessel for a pitched-blade. Rushton .turbine and A310 impellers. The tank and baffle dimensions, impeller sizes and placement locations are the same for all impeller types. The mixing performance .information summarized in Table-I is used to select an appropriate vessel configuration. Fill Level Optimization: The fill level in an unbaffled vessel is optimized by estimating .the free surface vortex draw down in the vessel. Over-filling the mixing vessel results in .increased power consumption and increased mixing time. Under-filling can result in .freesurface vortex interaction with the impeller. This can cause foaming and product .damage. The interaction of the vortex with the impeller can also lead to vibration of the .impeller shaft resulting in mechanical failure of the equipment. In this study, Visimix is applied to compute vortex drawdown depth for various .operating rpms. This is then used to estimate the optimum fill level of the mixing vessel. Solids Dissolution Predictions: In this study, dissolution of solids is examined. Tier-two .methods using Visimix are applied to predict solids dissolution behavior in mixing vessel .configurations at the lab scale, pilot scale and production scale. Figure 6 depicts .dissolution time for various impeller sizes and rpm. An appropriate impeller size and .speed is selected based on this analysis. The impact of various process parameters on .dissolution behavior at the various equipment scales is examined. Optimization of vessel .configuration and process conditions is carried out. Impeller Placement in Vessel: Tier-two methods can be applied to predict overall mixing .behavior such as, the impact of number of impellers on mixing behavior. However, these methods do not provide detailed information pertaining to impeller-impeller interaction .and its impact on flow behavior in the vessel. These issues are addressed using Tier-three .methods. In the present study, tier-three simulation methods are applied to examine the impact of impeller placement on flow behavior and hence mixing characteristics.

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A multi-tiered approach can be successfully applied for design, analysis and scale-up of .mixing processes. This solution strategy provides the flexibility of adopting the most .appropriate tool based on requirements. Sizing calculations for a new design can be .carried out using tier-one analysis. Important mixing parameters are estimated using tier .two analysis. A number of concepts can be rapidly examined using tier-two methods. .These methods can be applied to solve a number of mixing problems. Detailed .information not readily available can be obtained using tier-three methods. These .methods vary in rigor and provide information at various scales. This information can be .assimilated for selected processes to generate specific guidelines for design, scale-up and .troubleshooting of stirred vessels.

[4] Mixer Mechanical Design- Fluid Forces by Ronald J. Weetman’s and Bernd Giga’s Ronald J. Weetman’s and Bernd Gigas’s paper outlines the fluid forces that are imposed on impellers by the fluid continuum in the mixing vessel. The analysis shows that the forces are the result of asymmetries acting dynamically and transmitted from impeller blades to the mixer shaft and gear reducer. Several experimental techniques coupled with the role of computational fluid dynamics in mixer process and mechanical design is shown. When the mixer applications are varied. With these various processes occurring, the fluid motion in the tank is unsteady. This means that the loads on the individual impeller blades as well as the shaft, reducer, motors are dynamic. Normal current fluctuations at the motor is ± 5 to ± 15 percent from the mean. Typical load fluctuation on the shaft is about twice this and impeller blade load fluctuation if four times what occurs at the motor. Hence, The job of the designer is to be aware of the impact of mixing process conditions on these highly oscillating loads and their impacts on mixer components. Even with seemingly calm motion, there are severely fluctuating loads on the blades. Depending upon the magnitude and dynamics of the resultant bending loads on the mixer system, care is needed in the design of the individual mixer components. In addition to designing for the loads in the shaft, these loads are transmitted through the gearbox, mounting structure, and finally the tank. Power transmitted by the prime mover through the reducer and shaft which can be through the reducer and shaft is given as Power= Nρρ speed̂3 diameter3. Computational Fluid dynamic has been a great aid in understanding and showing details of mixing environments. Computational fluid dynamics can allow theoretical examination of the loads on the mixing blades as well as the flow field in the mixing vessel. Fluid forces at the impeller create a large bending moment which is usually the main critical design elements while the other factors are torque, thrust and including the weight. The

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mechanical design needed is usually at the top of the shaft where the combined bending and torsional stress are largest. Care is needed to avoid operating speeds that give rise to any amplification of forces caused by coincidence with natural frequencies of the shaft and tank structure.

[5] Mechanical Design of Mixing Equipment by David Dickey in Handbook Of Industrial Mixing – Science & Practice Because of the diversity of fluid mixing applications and variety of vessels, many different styles of mixers are used in industrial applications. Mixer sizes include small fractionalhorsepower portable mixers to huge 1000 hp plus mixers. Although normally viewed as a single piece of equipment, like a pump, the typical mixer is composed of several individual components, such as a motor, gear reducer, seal, shaft, impellers, and tank, which is often designed and purchased separately. Although highly customized for many applications, most mixers are a combination of standard components, sometimes with modifications, and often with unique characteristics, such as shaft length. Generalizations, especially for mixers, can misrepresent individual situations, but some features are common to the largest number of mixers built worldwide. The most common motive force for a mixer is an electric motor, so a knowledge of standard motor characteristics is useful. Most mixers operate at or below typical motor speeds, so some type of speed reduction is common. Speed reduction can be accomplished with several different types of gears, usually in enclosed housings, or with belts and sheaves. Besides speed reduction, antifriction bearings are found in all types of rotating equipment. Some type of seal around the rotating shaft is required for closed-tank operation and the type depends on degree of seal required, operating pressure, and operating temperature. The shaft for a mixer, especially a large one, involves significant mechanical design, partly because of the myriad of shaft lengths, impeller sizes, and operating speeds, and partly because both strength and rigidity are necessary for a successful design. The combination of custom process and mechanical design necessary for mixers is unique for chemical process equipment. Mechanical design does not end with the shaft, since strength and practical issues remain for the impeller. Another part of mixer design is the tank in which the mixer is used, since tank dimensions influence mixer features, especially shaft length. Conversely, a mixer requires tank features, such as baffles, support strength, and other tank internals. Materials of construction, although most commonly metal alloys for mixers, depend on process chemistry and operational requirements. Other mechanical features can be important in special-purpose mixers, such as high-shear mixers, dry-solids mixers, and static mixers. Without revealing trade secrets or emphasizing proprietary technology, elements of the same mechanical design considerations apply to special-purpose mixers. The primary mechanical emphasis in this chapter is on equipment discussed elsewhere in this book. Each key element of the mechanical characteristics of mixers will be covered in this section. Although not comprehensive with respect to each topic, the equipment and design requirements discussed should cover most of the mixer types and applications. Even with

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the diversity of mixing equipment, features such as motors and materials of construction are mechanical considerations, common to all types of mixers. Impeller-Type Mixing Equipment: Impeller-type mixing equipment represents the largest category of general purpose mixing equipment for fluid processing applications. From the process view of impeller-type equipment, an impeller, usually composed of blades mounted to a central hub and rotated by a drive shaft, pushes and moves the material to be mixed. The mixing action and the process results are primarily a result of this material, usually fluid, motion. The mechanical design of impeller-type mixing equipment is responsible for the process by which some form of energy, such as electricity, is converted into fluid motion. That fluid motion is ultimately dissipated as heat, hopefully after the process objectives are accomplished. To present an organized understanding of mixing equipment, some common terminology is used to describe typical characteristics. Each category of equipment has some loosely defined limits, often with overlap to other categories, depending on features provided by different manufacturers of the equipment. Top-Entering Mixers. The designation top-entering mixers has become accepted as a more restrictive term than the name would imply. Top entering mixers are usually considered the equivalent of portable mixers with flange mountings, or perhaps larger mixers but with light-duty gear drives and motors less than 10 hp (7460 W). This designation is less of a true definition than an accepted industry practice used to describe basic mixer products. By this definition, top-entering mixers have flange or pedestal mounts, compared with the clamp or swivel-plate mounts used on portables. Most top-entering mixers are mounted on the vertical centerline of a tank with baffles, but may be off-center or off-center, angle mounted. Longer shafts and larger impellers cause more severe loads on top-entering mixers than portable mixers. Most top-entering mixers have an axial flow impeller, such as a hydrofoil impeller or sometimes a marine propeller. Typical seals for top-entering mixers are basic stuffing boxes or single, mechanical seals. For reasons of mechanical strength, sealing pressures are typically 30 psig (207 000 Pa) or less. For reasons of cost, single dry-running mechanical seals are common. D.S Dickey’s and J.B Fasano’s study interacts with providing substantial practical information about the mechanical design of mixing equipment. Similarly, concentrating on impeller operation near liquid surface thereby considering mechanical loads acting on each parts and environmental influence on motor performance and enclosure

[6] Design and fabrication of bi directional mixer In this paper published in IJAREST in March 2017, the authors have designed and fabricated a bi-directional mixer for mixing powders, chemicals & semisolid works. A chemical mixer is being designed which consist of a container impeller blades, electrical motor, pair of pulleys, pedestal bearings and drive shafts. We are using the container made up of PVC; it is placed at about 6inches from ground, so that it is easy to pour the material for the workers preparing the chemical solution. The motor is placed vertically in order to mount the pulley and belt assembly on the motor shaft. This machine is designed to mix the cleaning solution used for cleaning the floors. In electrically powered system an

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electrical motor is used to run the motor shaft. As the motor shaft rotates, the pulley mounted on motor shaft also rotates. The power transmission will be takes place from motor to impeller shaft. As the impeller shaft rotates the impeller blades also rotate along the direction. And hence the mixing of chemical ingredients is obtained. The speed of the electrical motor is controlled using speed regulator. Design process involved selection of motor for the process design. Selected motor has following specifications: Single Phase AC motor of 50 watt power running at 60 rpm. The torque delivered by motor is calculated to be 7.96 N-m. Further, rope drive was designed and the dimensions were calculated which was followed by bearing selection. The gearbox was designed to deliver the required speed reduction at required torque. Thus bi-directional motor was designed and fabricated.

[7] Comparisional Study of Pitched Blade Impeller and Rushton Turbine in Stirred Tank for Optimum Fluid Mixing by S. Saravanakumar, P. Sakthivel, S. Shiva Swabnil and S. Rajesh This study was done by S. Saravanakumar, P. Sakthivel, S. Shiva Swabnil and S. Rajesh. This work compares the importance of impeller and tank geometry for two widely used impellers. For the Rushton turbine, power consumption is dominated by form drag, so details of the blade geometry and flow separation have a significant impact (30%) on the power number. For the PBT, form drag is not as important, but the flow at the impeller interacts strongly with the proximity of the tank walls, so changes in the position of the impeller in the tank can have a significant impact on the power number (15%) due to changes in the flow patterns. For both impellers, the importance of geometry decreases as the Reynolds number drops into the transitional regime and viscous forces come into play. From the data presented in this paper, it is concluded that: (1) Accurate torque measurement techniques have been established and documented. Results from three differ- ent labs are compared, and are in very close agreement. This level of accuracy goes a step beyond the classical results, which established generic power number curves for many standard impellers. (2) For pitched blade impellers at Re > 2 × 104, the power number is constant and Npft is an accurate representation of the data. For the Rushton turbine, there are changes in Np even above the nominal limit of 2 × 104. (3) There is no effect of blade thickness on power number for the 4bladed PBT impeller. The previously reported effect of blade thickness for the RT was replicated, and the curves extended down into the transitional regime.

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(4) The fully turbulent power number for the 4-bladed PBT impeller is a function of D=T. The variation is linear for the data collected here, with Npft = 1.5 -- 0.7(D/T) for (0.25 < D/T < 0.5) at C = T/3. (5)The angular momentum balance set out in equation provides a way to understand variations in power number as various aspects of impeller and tank geometry are changed. This analysis, however, is extremely sensitive and does not yield quantitatively satisfying results for either LDV or CFD measurements

[8] Study and Design of Impellers for Multiphase Reactors D. Devkumar’s D. Devkumar’s research paper gives a lot information about Designing and Calculations. Mixing in tanks is an important area when one considers the number of processes, which are accomplished in tanks. Essentially, any physical or transport process can occur during mixing in tanks. Qualitative and quantitative observations, experimental data, and flow regime identifications are needed and should be emphasized in any experimental pilot studies in mixing. In fact, the geometry is so important that the processes can be considered geometry specific. Solid suspension is very much dependent upon the shape of the tank bottom; liquid-liquid dispersion depend upon the geometry of the impeller; blending, upon the relative size of the tank to the impeller; and power draw, upon the impeller geometry. Mixing efficiency in a stirred tank is affected by various numbers of parameters such as baffles, impeller speed, impeller type, clearance, tank geometry, solubility of substance, eccentricity of the impeller. Flow patterns can be changed according to the type of impellers, and fall into three categories: axial, radial and tangential. Mixing at high solid concentration is a classical operation in process engineering. Solid-liquid mixing plays an important role in chemical, biochemical and mining processes dealing for instance with heat and mass transfer, transport and settling, dispersion, homogenization and/or coagulation Co-axial mixers are used in industry. The co-axial mixers have a specific design for the coating paper industry; it consists of a dispersion impeller (e.g. saw tooth type) and an anchor impeller. The production of sub-micron particles of organic actives has become of paramount importance in the pharmaceutical industry. So the impellers are used in the pharmaceutical industries. The other major applications of impellers are Oil industry, Polymer industry, Waste water treatment, Paint industry and Fermentation process. This project is aimed at the design of different impellers like pitched, paddle and turbine and also the analysis of these impellers by varying the physical properties and fluid properties with different dimensions. Finally to analyze the results of all the impellers to get an impeller with less power consumption and High gas holdup value. Following observations were made during this study:

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Comparison of Impellers Gas holdup is the amount of gas present in the given system. Compressed air is used as the gas for analysis. In this project, air (gas) is allowed to pass through water (liquid) and the mass transfer occurs. The level of water is raised by this procedure. The value of gas holdup is obtained through the graph sheet stuck on the vessel. The power and gas holdup of the three designed impellers are measured and tabulated in Table. It is found that the pitched blade impeller has lower power consumption and high gas holdup. So the pitched impeller is chosen for further analysis. Effect of Impeller Diameter: Three different dimensions of impeller diameter are taken as T/2(0.28 m), T/3(0.19m) and T/4(0.14m) and the pitched impeller with the blade angle 45 degrees is used. The impeller with the diameter of T/2 is found to give more gas holdup and consume less power. Effect of Clearance: Clearance is defined as the distance between the impeller and the bottom tip of the tank vessel. If the initial height and the final height are noted as H1 and H2 the percentage of the clearance is computed by, (H2-H1/H2) * 100. The readings are measured and tabulated in Table. It can be concluded that a clearance of t/3 is ideal. Effect of Liquid Height: The liquid height is varied at three different positions corresponding to H=T, H>t and H
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the characteristic of high shear stress and has a beneficial effect on generation of turbulence. This is helpful to flow mixing and particle dispersion. In this study we are concerned with the pitched-blade turbine the flow characteristics in certain ranges of blade angles 300 and 600 blade widths 0.2 D &0.4 D, and impeller diameters 0.25 T & 0.5 T. The pumping capacities and hydraulic efficiencies have also been reported. It was indicated that the hydraulic efficiency increases with the blade angle and the impeller diameter within the range studied. Besides the dominant vortex mentioned above, there may exist a smaller vortex, also induced by the discharge stream, located at the center region below the impeller. The diameter of the tank is denoted as T, and the height of the tank as H. There are four equally-spaced baffles fitted on the surrounding wall with a width B. The clearance of the impeller is C, which is from the center line of the blade to the bottom of the tank. The impeller holds six blades and has a diameter D. The blades have a pitch angle and a width W. To generate unstructured grids the computational domain is first divided into 40 blocks. In each block a simple method, such as an algebraic method, is used to create a suitable grid. After the grids for all the blocks are constructed, the grid nodes are readdressed. To validate the current mathematical model, computations have been performed to compare with the measurements of Ranade and Joshi. It can be seen that the velocities are accelerated quickly to reach a position roughly corresponding to the tip of the blade, followed by a gradual decrease. The negative axial velocity in the region near the side wall of the tank implies the existence of a circulation loop, i.e., an axial vortex there. The predictions capture these characteristics quite well, though, in comparison with measurements, some degree of discrepancy exists. More comparison in of pumping number and power number will be given later.. It needs to be emphasized here that the disagreement between the predictions and the measurements is partly attributed to the imperfection of the eddy viscosity model which cannot cope with such a complex vortex and swirling flow. Another factor affecting the prediction accuracy is the assumption of steady state. In a real situation the impeller blades keep changing their position relative to the baffles, but not in the numerical simulation.

[10] Significance of Axial Flow Pattern in mixing by Uhl and Gray, Gates, Hicks and Dickey The details on the section are provided by Uhl and Gray, Gates, Hicks and Dickey .In fluid agitation, the direction as well as the magnitude of the velocity is critical. The directions of the velocity vectors throughout an agitated vessel are referred to as the flow pattern. Since the velocity distribution is constant in the viscous and turbulent ranges, the flow pattern in an agitated vessel is fixed. During the mixing of fluids, it is essential to avoid solid body rotation and a large central surface vortex. When solid body rotation occurs, adequate mixing is not achieved because the fluid rotates as if it were a single mass. Centrifugal force of the fluid causes a central surface vortex to be thrown outward by the impeller. Entrainment of air results if the vortex reaches an impeller, resulting in reduced mixing of the fluids. This situation can be averted by installing baffles on the vessel walls, which impede rotational flow without

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interfering with radial or longitudinal flow. Effective baffling is attained by installing vertical strips perpendicular to the wall of the tank. With the exception of large tanks, four baffles are adequate to prevent swirling and vortex formation. For propellers, the width of the baffle should be less one-eighteenth the diameter of the tank; for turbines, less one-twelfth the tank diameter. Figure 888-9 shows the various flow patterns of radial and axial impellers. Reducing vortex formation may also be achieved by placing an impeller in an off-center position. Paddle agitators and flatblade turbines promote good radial flow in the plane of the impeller with the flow dividing the wall to form two separate circulation patterns. One portion flows down along the wall and back to the center of the impeller from below, and the other flows up toward the surface and back to the impeller from above. Propeller agitators drive the liquid down to the bottom of the tank, where the stream spreads radially in all directions toward the wall, flows upward along the wall, and returns to the suction of the propeller from the top. The flow pattern of a propeller agitator. Propellers are employed when heavy solid particles are suspended. flow patterns and applications of some commercially available impellers. Axial flow discharge coincides with the axis of impeller shaft, so when the impeller operates in a down pumping mode, the flow impinges on the bottom of the tank and spreads out in all directions toward the wall. The flow rises along the walls up the liquid surface and is pulled back to the impeller. Since axial flow impeller produce only one loop, fluids mix faster and blend time is reduced compared to radial flow impellers. The fluid does not take sharp turns near impellers and because of this, power consumption is less than that of radial flow impellers at the same speed and same the diameter.

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Chapter 3 OBJECTIVES

Through this project we plan to achieve the following objectives: 1. To eliminate the necessity of different setups for different mixing processes. 2. To design and fabricate a universal industrial mixer for mixing fluids of a range of viscosities. 3. To achieve maximum mixing efficiency. 4. To achieve portability for ensuring hassle free mixing at various stations.

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Chapter 4 METHODOLOGY The basic five-step process usually used in a problem-solving works for design problems as well. Solving a design problem is a contingent process and the solution is subject to unforeseen complications and changes as it develops. Until the Wright brothers actually built and tested their early gliders, they did not know the problems and difficulties they would face controlling a powered plane. The five steps used for solving design problems are: 1. Define the problem 2. Gather pertinent information 3. Generate multiple solutions 4. Analyze and select a solution 5. Test and implement the solution

Fig 2. Design steps 19

1. Define The Problem

Unlike an analysis problem, a design problem often begins as a vague, abstract idea in the mind of the designer. Creating a clear definition of a design problem is more difficult than, defining an analysis problem. The definition of a design problem may evolve through a series of steps or processes as we develop a more complete understanding of the problem.

Criteria for success are the specifications a design solution must meet or the attributes it must possess to be considered successful. At this point in the design process, the criteria are preliminary. As the design solution develops, we will most likely find that the initial criteria need to be redefined or modified. Preliminary criteria must not be too specific so they allow flexibility through the design process.

2. Gathering Pertinent Information

Before proceeding further into the design process, important specifications like viscosity of fluids, the fluid forces resulting from the process, motor specifications, design process for various mechanical components must be specified. Gathering pertinent information can reveal facts about the problem that result in a redefinition of the problem.

Traditional publications are an essential source of information to engineers and scientists. However, electronic information transfer and retrieval are quickly becoming a standard source for engineers and scientists. When you begin a search for information relating to a design problem, you must be prepared to go to many different sources. The library is still the primary source of information for an engineering student.

3. GENERATE MULTIPLE SOLUTIONS The next step in the design process begins with creativity in generating new ideas that may solve the problem. Creativity is much more than just a systematic application of rules and theory to solve a technical problem.

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We studied various existing solutions and analyzed each for their advantages and drawbacks.

3. ANALYZE AND SELECT A SOLUTION

We started with the existing solutions to the problem and analyzed them for any weaknesses or cons. Out of the studied existing solutions, we plan to select the most relevant solution for our problem. Further optimizing the selected solution by brainstorming to eliminate the process drawbacks. Following points need to be given due considerations.

3.1.Functional analysis This part determines whether the given design solution will function the way it should. Functional analysis is fundamental to the evaluation and success of all designs. A design solution that does not function properly is a failure even if it meets all other criteria.

3.2.Ergonomics Ergonomics is the human factor in engineering. It is the study of how people interact with machines. Most products have to work with people in some manner. People occupy a space in or around the design, and they may provide a source of power or control or act as a sensor for the design. For example, people sense if an automobile air-conditioning system is maintaining a comfortable temperature inside the car. These factors form the basis for human factors, or ergonomics, of a design.

3.3.Product Safety and Liability The primary consideration for safety in product design is to assure that the use of the design does not cause injury to humans. Safety and product liability issues, however, can also extend beyond human injury to include property damage and environmental damage from the use of your design. Engineers must also consider the issues of safety in design because

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of liability arising from the use of an unsafe product. Liability refers to the manufacturer of a machine or product being liable, or financially responsible, for any injury or damage resulting from the use of an unsafe product.

3.4.Detailed Approach To The Solution The detailed approach that is planned to follow during the course of project is demonstrated with the help of a flow chart

Selection of mixing fluid and quantity

Coupling design

Selection of bearing

Design of vessel

Shaft design

Design of portable frame

Selection of impeller design

Selection of motor

Testing & Optimisation

Fig 2. Detailed approach to the solution

5. Test and Implement the Solution The final phase of the design process is implementation, which refers to the testing, construction, and manufacturing of the solution to the design problem. Various activities included in this step are

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5.1. Prototyping The first stage of testing and implementation of a new product, called prototyping, consists of building a prototype of the product-the first fully operational production of the complete design solution. A prototype is not fully tested and may not work or operate as intended. The purpose of the prototype is to test the design solution under real conditions.

5.2.Documentation One of the most important activities in design is documenting your work, clearly communicating the solution to your design problem so someone else can understand what you have created. Usually this consists of a design or technical report. Communicating the solution to a design problem through language, both written and oral, is a vital part of the implementation phase.

5.3.Testing and Verification Testing and verification are important parts of the design process. At all steps in the process, you may find that your potential solution is flawed and have to back up to a previous step to get a workable solution. Without proper testing at all stages in the process, you may find yourself making costly mistakes later.

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Chapter 5 Design Step 1: Selection of fluid Viscosity is the property of a fluid which opposes the relative motion between two surfaces of the fluid that are moving at different velocities. In simple terms, viscosity means friction between the molecules of fluid. When the fluid is forced through a tube, the particles which compose the fluid generally move more quickly near the tube's axis and more slowly near its walls; therefore some stress (such as a pressure difference between the two ends of the tube) is needed to overcome the friction between particle layers to keep the fluid moving. Viscosity plays an important role in the design of mixer. It determines the power required for proper mixing of the fluid. Reynold’s (Re) number is given as

𝑅𝑒 =

𝜌𝑉𝐷 𝜇

Where ρ = Density of fluid V = Velocity of tip D = Diameter of impeller µ = Kinematic viscosity

If Re is < 2000 the flow is laminar If 2000< Re < 40000 the flow is transitional Whereas if Re > 4000 the flow is turbulent. Hence it is necessary to ensure that the flow is turbulent. Higher the viscosity lower is the Reynold’s number and hence flow becomes laminar which does not ensure proper mixing and the speed and diameter needs to be increased in order to compensate for the reduced Re number.

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In this step, in order to keep the solution feasible and economical we have chosen low viscosity fluids which can be mixed easily. After a preliminary study we found that fluids having viscosity in the range of 1-3 cP can be mixed using a low power motor making the solution feasible and economic. Density of the fluid also plays an important role in motor selection and influences the fluid forces acting on the shaft design. In order to keep fluid forces within safe range and to use a low power motor fluids having density approximately around water. Following are some of the fluids with their properties:

Fluid

Viscosity [cP]

Density [kg/m3]

Acetone

0.306

784

Benzene

0.6

876

Water

0.894

997

Milk

1.54

1026

Ethanol

1.74

789

Methanol

0.544

792

Nitrobenzene

1.863

1200

propanol

1.945

803

Table no: 1 Viscosities of fluids

Step 2: Vessel Design Quantity of fluid to be mixed had to be decided before doing further calculations as vessel dimensions have a huge impact on impeller design, forces acting on the shaft and the setup as a whole. After having a discussion with the professor vessel capacity was arbitrarily taken as 100 liters as it is readily available in the market and layout can be designed accordingly. First we studied the effects of vessel dimensions on the design to have a technical knowledge while selecting the diameter and height of the vessel. Following are the findings of the preliminary study. In his study D. Devkumar [8] designed and analyzed different impellers by varying parameters like impeller diameter, vessel diameter, clearance between impeller and the vessel, viscosity,

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liquid height and addition of electrolytes like glycerol, dilatants, etc. These impellers are tested and compared to get maximum gas holdup and minimum power consumption. For all comparisons and analysis, graphs are plotted between speed and gas holdup, power and gas holdup.

2.1 Effect of vessel diameter and height: The vessel diameter is varied at 0.75m, 0.57m and 0.3m and the values are measured and tabulated in Table no 1 and a graph is drawn accordingly.

Speed (N) (rps)

Power (P) (watts) T1 =0.75 m T2 = 0.57 m

2 3 4 5 6 7 8

9.68 32.69 77.5 151.3 261.5 415.3 620

2.46 8.29 19.65 38.38 66.32 105.37 157.2

T3 = 0.3 m 0.09 0.33 0.79 1.55 2.67 4.2 6.35

Table no. 2 Effect of vessel diameter

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Fig. 3 Table no. 2 Effect of vessel diameter

From the graph it can be inferred that power required for mixing does not vary significantly with change in vessel diameter however clearance plays an important role as seen in further study by D. Devkumar [8]. Hence, we have selected diameter of the vessel as 430 mm. Similarly, the study shows that height of the liquid does not affect the power consumption and hence we chose the height as 705 mm as an available vessel in the market.

Step 3: Layout Design This step involved design of layout to permit mounting of motor, its vertical motion, mounting and dismounting of the vessel for mixing of fluid. It is just a preliminary layout that we plan to follow during the rest of the design process. Dimensions are not fixed yet and will involve comprehensive calculations later in the design process. Following figure shows the layout modelled in solidworks.

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Fig. 4 Preliminary Layout

Step 4: Impeller Design The most important factors governing the selection of the impeller type include the power number and Reynolds number. The power number gives the amount of the consumed by the blade whereas the Reynolds number suggests the type of flow.

The power number is one of the most widely used design specifications in the mixing operation and has proven to be a reliable predictor of a number of process results. The power number can be calculated from the formula: 𝑁𝑝 =

𝑃 ρN3 D5

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Where Np is the power number P = Power consumed ρ = Density of fluid D = Diameter of the vessel N = Speed of impeller Flow number is also an important parameter to be taken into consideration while selecting an impeller. Formula of flow number is given by: 𝑁𝑞 =

𝑄 𝑁𝐷3

Where Q is the radial discharge

Typical values of flow number for various impeller are shown in the table below: Impeller Type Narrow blade hydrofoil Wide blade hydrofoil Pithched Blade Turbine Flat Blade Turbine Rushton Turbine HSD-Sawtooth

Power number 0.3

Flow number 0.52

0.7 1.50

0.66 0.80

3.0 5.00 0.10

0.80 0.65 0.05

Table no. 2 Impeller comparison

As observed from the table the least power number and the highest flow number is observed in the Pitched Blade Turbine. Hence we have selected Pitched Blade Turbine as our impeller

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Chapter 6 Expected Outcome At the end of the project we hope to have a solution to the problem i.e. to eliminate the necessity of different setups for different fluids. Also making it portable to ensure hassle free mixing at various stations. The solution would somewhat appear similar to the image shown below.

Fig. 5 Expected Outcome

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Chapter 7 REFERENCES [1] Tomáš Jirout, František Rieger, Impeller design for mixing of suspensions Czech Technical University in Prague, Faculty of Mechanical Engineering, Department of Process Engineering, Technická 4, 166 07 Prague 6, Czech Republic [2] Kazuhiko Nishi, Naoki Enya, Kazufumi Sonoda, Ryuta Misumi, Meguru Kaminoyama, Potential of an asymmetrical agitation in industrial mixing, Internat. J. Sci. Eng., Vol. 5(2)2013:73-80, October 2013 [3] H.S. Pordal & C.J. Matice, Design analysis and scale up of mixing processes [4] Ronald J Weetman, Bernd Gigas, Mixer Mechanical design – Fluid Forces, Proceedings of the 19 th international pump users symposium [5] David Dickey & J. B. Fasano, Industrial Handbook Of Mixing - Science & Practice Pg no 1247 – 1329 [6] Kushare D.A , Dhepale D.P. Ukirde A.S Lande S.C., Prof. Dange B.S., Design & Fabrication Of Bi-Directional Mixer International Journal of Advance Research in Engineering, Science & Technology (IJAREST) Volume 4, Issue 3, March 2017, eISSN: 2393-9877, print-ISSN: 2394-2444 [7] S. Saravanakumar, P. Sakthivel, S. Shiva Swabnil and S. Rajesh, 3037-3056 International Journal of Pure and Applied Mathematics Volume 119 No. 12 2018, [8] D Devkumar, K Saravanan, Study and design of multiphase reactors, Vol 2 Modern Applied Science, www.ccsenet.org

[9] Yeng- Yung Tsui, Jian-Ren Chou, Yu Chang Hu, Transactions of the ASME, Vol. 128, July 2006

[10] Uhl, V. W. and Gray, J. B., Eds. Mixing Theory and Practice, Volume 1, Academic Press Inc.,

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