liquid mixing apparatus manual

CONTENTS 1. FAMILIARIZE WITH TRAINER 1 - 2 2. INTRODUCTION 3 3. EXPERIMENT 1 4 - 5 4. EXPERIMENT 2 6 – 7 5. EXPERIMENT 3 8 - 9 6. EXPERIMENT 4 10 – 11 7. EXPERIMENT 5 12 – 16

FM112 Liquid Mixing Apparatus Operation Manual

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FLUID MIXING APPARATUS Installation and preparation 1. The apparatus required a electrical power of 240Vac 50Hz. It is important the equipment

must be properly connected to supply earth conductor, to prevent any electrical shock to the user.

2. The apparatus required water supply and drainage, it is suitable to installed in the area which utility water supply and drainage are available.


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Apparatus layout and descriptions Description is refer to figure.1 based on the figure’s label ID number.

ID number Descriptions 1 Acrylic cylindrical mixing vessel incorporates a drain valve, depth scale and a

removable set of baffles. The mixing vessel is mounted on a mild steel frame.

2 Mixer assembly c/w stainless steel shaft with bare end shaft for mounting various type of impeller, the mixer is direct driven by Electrical motor. The reaction force of mixer is measured by load cell and indicates on the digital panel meter. The mixer rotation speed is control by frequency inverter.

3 Load cell is installed to measures the mixer resultant force. The distance of centre mixer shaft to the load cell measure point is 60mm.

4 Electrical control panel is comprise of : 4.1. Safety residual current breaker. 4.2. Motor overload breaker. 4.3. Load cell amplifier and digital display unit. It indicates the mixing reaction force in Newton unit ( N ). 4.4. Frequency inverter 0.75kw for varies the motor speed. The inverter c/w digital display meter to shows the motor rotating speed in RPM. 4.5. Main power switch. 4.6. Mixer run switch. 4.7. Mixer speed adjustment potentiometer.

5 Impeller for testing, consists of : 5.1. Flat Paddle 6 x 3cm, 6 x 5cm. 5.2. Turbine impeller. 5.3. Screw propeller.

Care and caution during installation of impeller and experiment carry out. 1. Always fasten all the tightening screws. 2. Do not over filled the mixing vessel with any liquid. Keep the maximum level at 300mm. 3. Any ensure the working surrounding area is dry and clean.


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Introduction Mixing of liquid liquid or solid liquid systems is a complex operation to analyse and subject to many variables. The choice of mixer for a particular application depends on the degree of bulk movement or shear mixing required by the process. In order to predict full scale requirements it is usual to model the system and apply dimensional analysis. Before the dimensional analysis can be used three conditions must apply: 1. Geometric Similarity - This will define the boundary conditions; corresponding dimensions

will have the same ratio. 2. Kinematic Similarity - This requires that velocities at corresponding points must have the

same ratio as those at other corresponding points. 3. Dynamic Similarity - This requires that the ratio of forces at corresponding points is equal to

that at other corresponding points. Two modes of flow behaviour exist in a mixer: laminar and turbulent flow. Both these flow conditions may be described dimensionally but for turbulent flow its behaviour is less significant. In particular the Power number becomes independent of Reynolds’ number beyond a certain turbulence range. A further factor to consider is surface waves which are described by the Froude number group. In a mixer this phenomena is usually a function of the height of the vortex which forms. Armfield Limited have developed a model mixer which can be used to predict the power consumption of a full-sized mixer by equating Reynolds’ number and Froude number. The effect of placing baffles in the mixer vessel is also investigated.


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EXPERIMENT 1 Object Of Experiment: To observe the various flow patterns that can be achieved by the use of different impellers with and without the use of baffles. Equipment Set-Up: Fluid Mixing Apparatus filled with water up to a depth of 0.3m, flat paddle and turbine impellers, screw propeller, set of baffles, plastic pellets.


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Procedure: Attach flat paddle impeller with base of bush level with the end of the shaft. Add a small quantity of plastic pellets and make sure that the torque arm clamp is fixed. Turn up the speed of the impeller in small increments; say 25 r.p.m., until the pellets are seen to swirl around in the water. A vortex will be seen to form on the surface of the water. A small quantity of plastic pellets added to the water shows the mixing pattern of the liquid. Repeat the procedure with each impeller and again with the four baffles in position with each impeller. Observe the movement of dye and pellets in each case. When the concentration of dye becomes too high the tank should be drained and refilled with fresh water.

TYPICAL FLOW PATTERNS IN VESSEL WITH VERTICAL BAFFLES


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EXPERIMENT 2 Object Of Experiment: To show how the power consumed by a mixer varies with speed, type of impeller, and with the inclusion of baffles. Equipment Set-Up: Fluid Mixing Apparatus, with medium or light oil up to a depth of 0.3m, flat paddle and turbine impellers, screw propeller, set of baffles.

Summary Of Theory: Power (W) = Torque (T) x Angular Speed ω(rad/s) Torque (T) = Balance reading x 9.81 (Newtons) x torque arm radius (m) Note: Torque arm radius = 0.06m


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Procedure: Fill the tank up to a depth of 0.3m with light oil and attach the flat paddle impeller, 0.09m x 0.06m with the base of the bush level with the end of the shaft. Increase the speed control knob in gradual increments and record the speed on the speed indicator and the force on the forcemeter at each speed of the mixer. Repeat using the turbine impeller and other flat bladed paddles. The experiment can be repeated using angled rather than vertical paddles. Repeat with the baffles fitted with each flat paddle and the turbine impeller. Results: Flat paddle blade

Draw a graph of Power against Speed. Repeat table and draw graph for each impeller.

∆ Flat bladed impeller (0.09 x 0.06m) without baffles

Flat bladed impeller (0.09 x 0.06m) with baffles

Turbine impeller without baffles

Turbine impeller with baffles

Discuss the shape of the curves.


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EXPERIMENT 3 Object Of Experiment: To observe how different types of impeller turning at different speeds influence the rate of dispersion of solids throughout the liquid. Equipment Set-Up: Fluid Mixing Apparatus with water to a depth of 0.3m, flat paddle and turbine impellers and screw propeller, 1kg of fine sand (or alternatively graded coal 14-100 microns).

Summary Of Theory: The mixing of solid powders into a liquid depends on two main factors: shear rate of the suspension around the tip of the impeller, and the rate of overall circulation of the liquid and solids through the high shear region. Both contribute to the power needs of the mixer and the best one would be selected to suit a particular solid and liquid E.g. clay, calcium carbonate, starch, powdered foods, minerals, paints, dyes etc. in water, oil etc. A typical optimum arrangement would be a turbine impeller rotating at high speed, one third of the liquid level from the bottom and using four baffles.


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Procedure: The tank is filled with water up to a depth of 0.3m 1/2kg of fine sand is sprinkled on to the base of the tank. Attach the flat blade impeller with the centre of the impeller 0.15m from the base of the tank. Increase the speed of the impeller in small increments observing the lifting capacity, dead spots and movement of the sand particles. Take care that the level of the liquid does not spill over the top of the tank as the vortex forms. Repeat the experiment at several lower settings of the impeller on the shaft. Repeat at a lower level with the blade angles tilted to give a variable component of lift to the sand particles. Repeat using the turbine impeller at different levels. Repeat using the screw propeller at different levels. Repeat using all the impellers with the baffles fitted. Results: Discuss the effectiveness of each configuration of impeller and baffles. Determine which is the best for this application, and at what recommended speed.


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EXPERIMENT 4 Object Of Experiment: To observe the effectiveness of different impeller configurations running at different speeds, with and without baffles, on the mixing of immiscible liquids. Equipment Set-Up: Fluid Mixing Apparatus with water to a depth of 0.15m and light oil to a depth of 0.15m on top of the water making a total depth of 0.3m, flat paddles, turbine impeller, screw propeller and baffles.


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Procedure: Attach the flat bladed paddle (0.075 x 0.06m) with its centre-line 0.15m from the base of the tank. Increase the speed in small increments and observe the rate of mixing between the two liquid components. Repeat with the impeller at two further levels one 0.05m below and one 0.05m above the original level. Repeat with the turbine impeller. Repeat with the screw propeller. Repeat with all the impellers with the four baffles in position. Results: Discuss the effectiveness of each impeller type and level, with and without baffles. Determine the acceptable speed range for each impeller/baffle configuration.


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EXPERIMENT 5 Object Of Experiment: To predict the power absorbed by a large mixer using the Fluid Mixing Apparatus provided as a model and to draw a characteristic mixing curve. Equipment Set-Up: Fluid Mixing Apparatus filled with light oil up to a depth of 0.3m. Flat paddle impeller (90 x 60 mm), baffles fitted, viscometer or value of viscosity from suppliers, viscosity/temperature curve.

Summary Of Theory: For most applications the simplest method of predicting power consumed in a large mixer is by the power-per-unit volume method. Firstly the model is tested to achieve the flow patterns or mixing quality desired then the speed is determined of the full size mixer from one of the following relationships.


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For similar shear rates equate impeller tip speeds

For similar flow patterns and general mixing quality equate Reynolds' numbers

For similar fluids the speed of the large mixer is given by the equation For similar surface waves equate Froude numbers


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The power of the large mixer is given by the power absorbed by the model at the equivalent speed multiplied by the ratio of the volumes.

The characteristic curve is given by a plot of Power number - v - Reynolds' number (Reynolds' number on the horizontal axis). Power number Po is given by the expression:

The power absorbed by the model is calculated at each speed from the equation: P = Tω

where T = torque required to drive the impeller

= balance reading x 9.81 (Newtons) x torque arm radius (m)

and w = Angular speed (rad/s)

Note: Torque arm radius = 0.11m Procedure: Attach the flat blade impeller, (0.075 x 0.06m) with the base of the bush level with the end of the shaft. Release the balance adjustment clamp, and allow the dynamometer arm to move freely. To set the dynamometer arm to a neutral position, use the setting bar and adjust the tension spring as necessary. Adjust the length of the cord so that the indicator aligns with the mark on the datum plate in the neutral position. Increase the speed of the impeller through increments of 25 r.p.m. and record the power and speed until air is entrained at the centre of the paddle or the liquid gets near to the top of the tank. Repeat using the turbine impeller and again with both impellers without baffles. Depending on the viscosity of oil chosen, some difficulty may be experienced obtaining power measurements of sufficient accuracy for plotting the characteristic curve of the smaller impellers.


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Results: Test 1: Paddle impeller (0.075m x 0.06m)

4 Baffles Oil viscosity 0.15 Ns m-2 Oil density 900 kg m-3

Typical characteristic curve of Power number - v - Reynolds' number


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To predict speed and power consumed by a geometrically similar mixer. Using equal tip speeds method: Assume large mixer is 1.0m diameter then if the small mixer gives an acceptable shear rate at 200 r.p.m. and consumes 25W (when D = 0.16m). The large mixer should run at and the power consumed should be approximately

liquid mixing apparatus manual

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