Report Liquid Mixing Submit

UNIVERSITI TEKNOLOGI MARAFAKULTI KEJURUTERAAN KIMIA

CHEMISTRY LABORATORY(CHE 235)

NAME OF GROUP MEMBER : AFIF BAZLAA BINTI JUWAHIR

MATRIC NUMBER : 2010770233

GROUP : EH220 (2)

EXPERIMENT : EXPERIMENT 4 : FLUID MIXING

DATE PERFORMED : 24 OCTOBER 2011

DATE REPORT SUBMITTED : 3 NOVEMBER 2011

SEMESTER : 2

LECTURER : CIK NORHAYATI BINTI TALIB

CriteriaPoint

(rubric)Total Marks Marks

Abstract

Objective

Material and

apparatus

Procedure

Data/Result

Calculation

Discussion

Conclusion

References

TOTAL

Checked by: Rechecked by:

ABSTRACT:

The objective of this experiment is to observe the various pattern of water movement

during mixing processes that been create by the use of different impeller paddles with and

without the use of baffles, to find out the most efficient paddle for mixing processes and to find

out the power consumed by the paddle in order to mix oil during mixing processes. During

experiment 1 a), the mixing apparatus is set up with a flat paddle and filled up with 30 L of

water. Ball bearings are put into the tank. The power and the speed control are switched on.

The movements and the pattern of the movements of ball bearings are observed, recorded and

sketched during mixing. Same steps are repeated by using turbine paddle and screw paddle. For

experiment 1 b), same step are repeated as experiment 1 a) unless the water is replaced by oil

and use only flat paddle. The angular speed (r.p.m) and torque (Nm-2) are recorded. The

calculations are made to find the angular speed (rad/s) and power (watt) to draw a graph. The

calculations can be made by using the formula:

Power (P) : torque (T) X angular Speed (rad)

Angular speed (Ѡ) : r.p.m x 2ԓ/60 = rads⁻ˡ

The conclusion for this experiment is flat paddle are the most efficient paddle to use for mixing

based on the observation.

OBJECTIVE:

To observe the various of water flow patterns during mixing processes by the use of

different impeller paddles with inclusion or exclusion of baffles.

To show how the power consumed by a mixer varies with speed, type of impeller, and

with the inclusion of baffles.

INTRODUCTION

The simplest and common fluid mixing application is simply to add liquid “A” to “B”

where the liquids are soluble in one another and blend them uniformly. Mixing impellers are

designed to pump fluid through the impeller and produce turbulence which both of these

effects are essential to mixing. They produce fluid velocity and fluid shear respectively. Fluid

velocity produces movement throughout the mixing vessel, intermixing material in one part of

the tank with another, prevents solids from setting out and produces flows. Fluid shear in the

form of turbulence teddies is essential to micro-mixing within the large velocity streams

breaking up gas bubbles or immiscible liquids into small droplets. All mixing impellers produce

both fluid velocity and fluid shear but different types of impellers produce different degrees of

flow turbulence.

In industrial mixing applications, the power consumption per unit volume of fluid is used

extensively for scale up, scale down and design. In widespread use, the dependence of power

consumption on impeller and tank geometry is defined only in the most general terms. This is

due to the difficulty of obtaining accurate torque measurements on the small scale and due to

the predictive limitations of drag theory, particularly for recirculation three dimensional flows.

The power number is one of the most widely used design specifications in the mixing

operation has proven to be a reliable predictor of a number of process results. Power number is

sensitive to the details of impeller geometry and particular to the blade thickness but it is

independent of the impeller diameter to the tank diameter ratio. Power can be affected by

blade’s angle, thickness, chamber and number on impeller performance. A significant limitation

of theoretical is the assumption that there is no interaction between the impeller and the tank

walls .Power numbers assume fully baffled vessels with water like fluid and proximity correction

factors (off bottom and multiple impellers) of 1.0.

Some processes such as flocculation are shearing sensitive and require high flow and

low shear mixing. Other processes such as gas dispersion are at the other end of the scale and

require high shear mixing. The selection of the mixer for a particular application depends on

numerous process factors which are type of application (high flow or high shear requirements),

viscosity, %solids, amount of gas addition, tank geometry and retention time. Fluid’s density

affected the power draw of a mixing impeller. The power draw increases with increasing

viscosity. The viscosity of a fluid can have significant impact on the overall mixer sizing for a

particular application. The main sizing criteria consist of torque invested into the mix, impeller

style, impeller Diameter to Tank Diameter (D/T) Ratio, mixer horsepower, pumping capacity,

superficial velocity and torque volume.

MIXING FLUID MACHINE AND ITS FUNCTION:

1. Mixing of fluid depending on purpose that depends on the processing step.

Such as:

i. Suspending solid particles

ii. Blending miscible liquids

iii. Dispersing a gas through the liquid in the form of small bubbles

iv. Promoting heat transfer between the liquid and coil or jacket.

2. Mixing equipment:

i. Vessel – cylindrical shape

ii. Paddles

Styles :

o Radial flow

- multiples flat blades mounted parallel to the axis the mixing shaft

- use in high shear, gas/liquid dispersion, low level mixing

o Axial flow

- blades that make angles of less than 90° with the mixing shaft axis

- use in moderate shear & moderate flow, high intensity mixing for flow dependent

applications

Flat paddle

Slightly lower efficiency, compensated by easier fitting of liners.

Required slower speeds and greater gear reduction than propeller, high power per unit volume.

Limited to maximum speed

Radial flow pattern

Screw paddle

Axial flow parallel to the shaft and modified by baffles, a downward flow.

Operates over wide speed range

Very good at high speed, but not generally used.

Low speed it is not easily destroyed.

Not effective in viscous liquids

Turbines

Convert the energy of a moving stream of water, steam, or gas into mechanical energy.

Design in curved blade to catch the wind’s energy for flutter and spin.

Design for use in wetting out powders, dispersing fine solids, and creating emulsions.

Baffles

A flow-directing vane or panel in some vessel.

Will effected the suppressing vortex formation, increasing the power input and improving

mechanical stability.

It purpose to convert swirling motion into a preferred flow pattern.

Without baffles swirling motion approximates solid-body rotation in little mixing will be occur. It

because during agitation of a low-viscosity liquid, the rotating impeller impart tangential

motion to the liquid.

3. The flow pattern of the mixing depends on: the type of impeller; the characteristics of

fluid; and the size of vessel and baffles.

4. There are three components of the velocity of fluid and it flow depends on the

variations of the velocity components:

Radial – direction perpendicular to the shaft of the impeller.

Longitudinal – direction parallel with the shaft

Tangential or rotational – direction tangent to a circular path around the shaft.

It functions as dispersion of gas into liquid, dispersion of insoluble liquids into one

another and heat transfer applications.

It been design to pump fluid through the impeller and produce turbulence.

It produces fluid velocity and fluid shear, if different types of impellers will produce

different degrees of flow and turbulence.

Fluid velocity produced the movement throughout the mixing vessel, prevents solids

from settling out and produces flow over heating or cooling coils.

FORMULA:

Power (P) : torque (T) x angular Speed (rad)

Angular speed (Ѡ) : r.p.m x 2ԓ/60 = rads⁻ˡ

MATERIAL AND APPARATUS:

1) Mixing equipment model IM 103

2) Mixer controller

3) Mixer head

4) Yellow Beads

5) Impeller

-Flat blade paddle

-Screw blade paddle

- Turbine blade paddle

DIAGRAM OF MACHINE :

PROCEDURES:

Experiment 1a) - Using Water

1. Firstly, the mixing apparatus (Kesser FM1120) is set up with a flat paddle.

2. The tank is filled up with 30 L of water. Make sure the flat paddle is entirely in the water.

3. 10 ball bearings are put into the tank. It is to show the movement of water molecules.

4. The power is switched on to run the mixing machine.

5. The speed control is set to 1 and then followed by 2 and 3.

6. The movements of ball bearings are observed.

7. The pattern of the movements of ball bearings during mixing are recorded and

sketched.

8. Step 1 until step 7 is repeated by using turbine paddle and screw paddle.

9. All the data recorded.

Experiment 1b) – Using Light Oil

1. The tank is filled up to the depth of 30 L or 0.3m with light oil.

2. The flat paddle impeller is being attached, with the base level with the end of the shaft.

3. The power is switched on to run the mixing machine.

4. The speed control knob has been increased in gradual increments, the speed control is

set to 1 and then followed by 2 and 3.

5. The angular speed (r.p.m) and torque (Nm-2) are recorded. The readings can be obtained

from the meter at the machine.

6. The movements of ball bearings are observed.

7. The pattern of the movements of ball bearings during mixing are recorded and

sketched.

8. The calculations are made to find the angular speed (rad/s) and power (watt).

9. All the data are tabulated and a graph is made from the data recorded.

RESULT AND CALCULATIONS :

In light oil;

Result without baffles;

Angular Speed,

[r.p.m]

Angular Speed,

[rad/s]

Torque, T

[Nm-2]

Power, W

[watt]

50 5.236 0.01 0.05

100 10.472 0.16 1.68

150 15.708 0.31 4.86

200 20.944 0.52 10.981

250 26.180 0. 80 20.994

300 31.416 1.11 34.872

Result with baffles;

Angular Speed,

[r.p.m]

Angular Speed,

[rad/s]

Torque, T

[Nm-2]

Power, W

[watt]

52 5.236 0.26 1.361

100 10.472 0.59 5.969

150 15.708 0.99 19.923

200 20.944 1.45 29.317

250 26.180 1. 84 50.789

300 31.416 2.48 77.598

Calculations:

a) Without baffles

1. Angular speed = 50 r.p.m X 2π / 60

= 5.236 rad/s

Power = 0.01 Nm-2 X 5.236 rad/s

= 0.05 W


= 10.472 rad/s

Power = 0.16 Nm-2 X 10.472 rad/s

= 1.68 W


= 15.708 rad/s

Power = 0.31 Nm-2 X 15.708 rad/s

= 4.86 W


= 20.944 rad/s

Power = 0.52 Nm-2 X 20.944 rad/s

= 10.891 W


= 26.180 rad/s

Power = 0.80 Nm-2 X 26.180 rad/s

= 20.944 W


= 31.416 rad/s

Power = 1.11 Nm-2 X 31.416 rad/s

= 34.872 W

b) With baffles


= 5.236 rad/s

Power = 0.26 Nm-2 X 5.236 rad/s

= 1.361 W


= 10.472 rad/s

Power = 0.57 Nm-2 X 10.472 rad/s

= 5.969 W


= 15.708 rad/s

Power = 0.95 Nm-2 X 15.708 rad/s

= 19.923 W


= 20.941 rad/s

Power = 1.40 Nm-2 X 20.941 rad/s

= 29.317 W


= 26.180 rad/s

Power = 1.94 Nm-2 X 26.180 rad/s

= 50.789 W


= 31.416 rad/s

Power = 2.47 Nm-2 X 31.416 rad/s

= 77.598 W

a) With baffles

Power (W)

50 100 150 200 250 3000

5

10

15

20

25

30

35

40

45

50

Angular speed (r.p.m)

Figure 1

b) Without baffles

Power (W)

Angular speed (r.p.m)

Figure 2

DISCUSSION

50 100 150 200 250 3000

10

20

30

40

50

60

70

80

90

The mixing intensity can be varied widely by choosing a suitable impeller type and by

varying agitating speeds. The mechanical agitation is effective for the suspension of cells,

oxygenation, mixing of the medium, and heat transfer. Difference shapes of impeller produced

difference shape of flows, with radial flow impellers; the liquid is pushed towards of the

container, along the radius of the container. Flat impellers, the liquid is pushed in a downwards

directions; that is along the axis of the container. Baffles also usually installed to prevent a

vortex formation which can reduce the mixing efficiency and is to promote turbulence flow,

therefore better mixing. Baffles also needed to stop the swirl in a mixing tank because almost

all impellers rotate in the clockwise or counter-clockwise direction. Without baffles, the

tangential velocities coming from any impellers cause the entire fluid mass to spin. It may look

good from the surface seeing that vortex all the way down to the impeller, but this is the worst

kind of mixing. There is very little shear and the particles go around and this is more like a

centrifuge than a mixer. From the observation made, there is difference flow pattern produced

between using baffles and without. The yellow beads seem to be widely spread when using the

baffles and using the flat blade propeller. During agitation of a low-viscosity liquid, the rotating

impeller imparts tangential motion to the liquid. Without baffling, this swirling motion

approximates solid-body rotation in which little mixing actually occurs. The primary purpose of

baffling is to convert swirling motion into a preferred flow pattern to accomplish process

objectives. The most common flow patterns are axial flow, typically used for blending and solids

suspension, and radial flow, used for dispersion. However, baffling also has some other effects,

such as suppressing vortex formation, increasing the power input and improving mechanical

stability. A common agitation objective is suspending settling solids in a low-viscosity liquid. In

the exclusion of baffle in the vessel, the swirling flow field is ineffective at dispersing the solids

that are grouped in a rotating pile below the pitched-blade impeller. Also, a large surface vortex

is visible at the top of the shaft. In the vessel on the right, the baffles are visible on the left and

right sides of the vessel and as a thin gray strip that bisects the impeller and shaft. The presence

of baffles produces axial flow, in which the discharge flow produced by the impeller impinges

on the base of the vessel, flows radialy to the vessel wall, then up the wall, returning to the

impeller from above.

Mixing process without using baffles produces inconstant flow, as the result the beads

not mixing well but only stack at the bottom of the container. Even the high speed applied, but

the beads cannot mix well and vortex formed. Difference when the baffles used, the vortex not

forms and the beads mixed well. This means the baffles can prevent the formation of vortex

thus enhance the mixing process. Based on this experiment, the best impeller chosen is flat

blade propeller. By using this impeller, the mixing occurred uniformly from bottom to the top of

the container. When mixing, the speed cannot be too fast because to prevent formation of

bubbles, because bubbles can decrease the mixing rate.

CONCLUSION

Based on the graph obtained, the flat blade paddle produced constant and high flow

pattern, rather than screw blade paddle and turbine blade paddle. The constant flow important

to get the effective separations between particles and the medium, if the flow moves much

rapidly, the particles not separates well and can cause the medium become turbid and the

separation not occurred effectively. The flow control is important in separations by using the

impeller. If too slow movement of flow, the separation also cannot occur, because it is to gentle

to separates the particles

RECOMMENDATION :

Wear jeans or slack, a long sleeved shirt, and sturdy shoes that give good traction on

possibly wet floors.

Guard against electrical hazards by making sure that all equipment is well grounded

using three-wire plugs and other means.

During the undergoing experiment, students are advised to wear goggle and disposable gloves.

Since the experiment involved with hazardous chemicals, the utilities will provide protection for

students.

REFERENCES

i. Chapple D, Kresta M.S, Wall A and Afacan A (2002). ” The effect of impeller and tank

geometry on power number for a pitched blade turbine”. Volume 80, Part A.

ii. Anon (1998). “Mixing Fundamentals”. Page 1.01 Rev 2. Hayward Gordon LTD.

(http://www.haywardgordon.com/documents/Mixing_Fundamentals.pdf)

iii. http://www.wmprocess.com/impellers-for-mixing-processes .

iv. IChemE.http://www.clevelandmixers.com/Files/Torque%20paper%20as%20published

%20~1.pdf)

http://www.wmprocess.com/impellers-for-mixing-processes

http://www.haywardgordon.com/documents/Mixing_Fundamentals.pdf

APPENDICES

Flat Blade Paddle

Side View

Turbine Blade Paddle

Top View

Water Flow Patterns :

Without baffle;

Flat paddle

Turbine paddle

Screw paddle

With baffles ;

Flat paddle

Turbine paddle

Screw paddle

Documents

Report Liquid Mixing Submit