Thermofluids Lab : Fluid Mixing

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UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN KIMIA THERMOFLUIDS LBORATORY CGE 536 NO TITLE ALLOCATED MARKS (%) MARKS 1. ABSTRACT / SUMMARY 5 2. INTRODUCTION 5 3. AIMS / OBJECTIVES 5 4. THEORY 5 5. APPARATUS 5 6. PROCEDURES 10 7. RESULT 10 8. CALCULATIONS 10 9. DISCUSSION 20 10. CONCLUSIONS 10 11. RECOMMENDATIONS 5 12. REFERENCES 5 13. APPENDICES 5 TOTAL 100 0 NAME : 1) FATEN AMIRA BINTI HAMIDI (2014404804) 2) NOOR AYUNI BINTI MOHAMAD SOUFI (2014801628) 3) MUHAMMAD FATHUL ISLAM BIN ISMAIL (2014236014) 4) RIDZUAN BIN MAT ISA (2014637524) EXPERIMENT : FLUID MIXING DATE PERFORMED : 20 OCTOBER 2015 SEMESTER : 3 PROGRAMME : BACHELOR (HONS) OIL AND GAS ENGINEERING / EH 243 GROUP : EH243 3B

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Fluid Mixing Lab Report

Transcript of Thermofluids Lab : Fluid Mixing

Page 1: Thermofluids Lab : Fluid Mixing

UNIVERSITI TEKNOLOGI MARAFAKULTI KEJURUTERAAN KIMIA

THERMOFLUIDS LBORATORYCGE 536

NO TITLE ALLOCATED MARKS (%)

MARKS

1. ABSTRACT / SUMMARY 52. INTRODUCTION 53. AIMS / OBJECTIVES 54. THEORY 55. APPARATUS 56. PROCEDURES 107. RESULT 108. CALCULATIONS 109. DISCUSSION 2010. CONCLUSIONS 1011. RECOMMENDATIONS 512. REFERENCES 513. APPENDICES 5

TOTAL 100

REMARKS :

CHECKED BY :

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NAME : 1) FATEN AMIRA BINTI HAMIDI (2014404804) 2) NOOR AYUNI BINTI MOHAMAD SOUFI (2014801628) 3) MUHAMMAD FATHUL ISLAM BIN ISMAIL (2014236014) 4) RIDZUAN BIN MAT ISA (2014637524)

EXPERIMENT : FLUID MIXINGDATE PERFORMED : 20 OCTOBER 2015SEMESTER : 3PROGRAMME : BACHELOR (HONS) OIL AND GAS ENGINEERING / EH 243GROUP : EH243 3B

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Table Of Contents

Abstract………………………………………………………………………………………………….…2

Introduction……………………………………………………………………………………………….3-5

Objective…………………………………………………………………………………………………...6

Theory……………………………………………………………………………………………………...7

Apparatus………………………………………………………………………………………………….8

Procedure………………………………………………………………………………………………..9-10

Result…………………………………………………………………………………………………..11-14

Sample Calculation……………………………………………………………………………………….15

Discussion……………………………………………………………………………………………16-17

Conclusion………………………………………………………………………………………………18

Recommendation………………………………………………………………………………………..19

References……………………………………………………………………………………………….20

Appendices……………………………………………………………………………………………21-22

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1.0 Abstract / Summary

As for the fluid mixing experiment, we had completed eight sub experiments to study the flow

patterns under various conditions and to show how the power consumed by a mixer varies with

speed, type of impeller, and with inclusion of baffles. Practically, we are to determine the flow

patterns based on two choices of type of liquid. The flow patterns are distinguished by observing

how the two different mixtures are flowing in the tank. These flow patterns are dependent on the

type of impellers used and their position. Besides observing and determining the flow patterns,

we are needed to show how the power consumed by a mixer varies with speed, type of impeller,

and with the inclusion of baffles. The power can be calculated in the form of power number

which will further be discussed. For the first experiment, we have determined that different

impellers indeed results in different flow patterns with two different types of mixture. The

presence or absence of baffle in the mixing tank also can impact the flow pattern. Photos

showing the differences in flow patterns are attached in the results section of the report. As for

the second experiment, the power consumed by the mixer is calculated and the result obtained is

interpreted in the form of graph where we can see the relation between the power and the angular

speed. The results from this experiment are not 100% accurate due to some errors during

conducting the experiment. Thus, we added some recommendations to further improve this

experiment and to avoid the errors as much as possible.

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2.0 Introduction

Generally, the basic concept of fluid mixing is simply put as mixing fluid ‘X’ into fluid

‘Y’ where the liquids are soluble to one another and form a homogeneous mixture. Mixing

impeller specially designed to pump fluid through the impeller and produce turbulence which

this effect is vital in mixing operations. These produces 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 turbulent eddies 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.

The impeller flow patterns give impact to the result of mixing process. The flow pattern

depends on the impeller type which gives variation in flow patterns resulting from different

impeller types. The presence of baffle in mixing tank would influence the flow patterns as well.

It can increase the amount of top to bottom circulation which contributes to turbulence by giving

out some obstacles for the mixture to swirl as a whole and elimination of vortexes. The two main

types of the flow patterns are axial radial. The differences in the flow patterns can cause

variations in distribution of shear rate and energy dissipation rate within the mixing tank. In this

experiment, not only the fluid patterns of the fluid are determined, but also to show how the

power consume by a mixer varies with speed, type of impeller, and with and without baffle.

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2.1 Impellers

Impellers are rotating devices that force liquids, gases and vapors in a desired direction.

They are widely used in pumping, blowing, and mixing applications. This area gives the ability

to search for impellers for pumping and mixing of media and allows selection of type of impeller

and size. Impeller applications, specifications and features, types, and materials are all important

parameters to consider when searching for impellers. The five types of impeller that used in the

experiment which are axial propeller, turbine propeller, flat blade paddle 1.5 inch diameter flat

blade paddle 2.0 inch diameter and flat blade paddle 3.0 inch diameter.

Axial flow impellers are used at high speeds to promote rapid dispersion and are used at

low speeds for keeping solids in suspension. Axial flow propeller impellers are impellers that

have 2 to 4 blades and convey the pumped media in the direction along the revolving axis of the

impeller. Turbines propeller are impellers that have multiple fins and convey the pumped media

in the direction along the revolving axis of the impeller. Flat blade impellers are used for mixing

and have one or more paddles. Beside that flat blade paddle have a different diameter of paddle.

The common applications served by impellers include mixing, pumping, air movement,

chemical, compressor or refrigeration, heat exchangers or radiations, high viscosity media,

propulsion, and water or wastewater. Important impeller specifications to consider include the

number of blades or vanes, outside diameter, and bore size. Features include adjustable pitch,

anti-static, coated or plated, corrosion resistant, custom fabricated, folding blades, and

multistage. Choices for materials of construction include aluminum, brass or bronze, cast iron,

composite, plastic, rubber, stainless steel, and titanium.

2.2 Axial Flow

Axial flow is the patterns where the fluid or gas is flowing parallel to the axis turbine.

There are many impellers that produce axial flow which are propeller, pitched blade turbines,

and hydrofoils. An axial flow propeller exhibits a flow pattern throughout the entire tank volume

as a single stage. It imposes necessarily bulk motion, and is used to on homogenization

processes, in which increased volumetric flow rate is necessary.

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2.3 Radial Flow

Radial flow is the pattern that the working fluid flowing mainly along the radii of rotation

in the tank. Radial flow impellers produce two circulating loops, one below and above the

impeller. Mixing occurs between the two loops but less intensely than within each loop. These

impellers impose necessarily shear stress to the fluid, and are used to mix immiscible liquids or

generally, when there is a deformable interface to break. Besides, they are used for the mixing of

very viscous fluid.

2.4 Power Consumed

The power input is influenced by the geometry of the equipment and also the properties

of the fluid. The flow pattern and degree of turbulence are key aspects of quality of mixing. The

power input, P to an impeller of diameter, D driven at rotational speed, N in a fluid of density, ρ

and viscosity, μ can be expressed in terms of a dimensionless Power number, P

N 3 D5 ρ

2.5 Relevant Equations

Power ( P ) = Torque ( Ʈ ) x Angular Speed ( ω ) ( rads-1 )

Torque ( Ʈ ) = Force recorded on spring balance ( F ) x length of torque arm ( 0.11m)(r)

Torque arm (r) = 0.11m

Angular speed (ω) = N ( r.p.m. ) x 2 π60

= rads-1

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3.0 Objectives

Experiment 1 : To observe the various flow patterns that can be achieved by the use of different

impellers with and without the use of baffles.

Experiment 2 : To show how the power consumed by a mixer varies with speed, type of

impeller, and with the inclusion of baffles.

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4.0 Theory

Many type of impeller were used in this experiment and some of it are propeller and turbine

impeller. Turbine impeller is a rotating component which transfer energy from motor to the fluid. The

velocity that achieved by impeller is transfer into pressure when the outward movement of fluid is

confined by the container.

In this experiment, baffle are needed to stop the swirl in mixing tank. Most of common baffle

used are straight flat plate of metal that run along the straight sides of vertically oriented cylindrical tank.

For the unbaffle tank, tendency for swirling flow pattern to develop rotating liquid. However, there is a

limit to rotational speed that used. If exceed the limit of the rotational speed fluid will spill out of the

container.

In laminar flow (NRE<10), the same power were used by the impeller. The flow pattern may be

effected by the baffle but it not favorable. To allow the fluid circulate and produce axial deflection we

may need the baffle.

In transitional flow (10<NRe<10,000), the circulation of pattern will be clear when the tank is

unbaffle but the vortex will disturbed the pattern.

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5.0 Material and Apparatus

Fluid Mixing Apparatus

Flat paddle

Turbine impeller

Screw propeller

Speed controller

Force indicator

Tank

Baffles

Tank

Motor

Water

Hydraulic Oil

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6.0 Procedure

General Start-up procedure

1. The power outlet is switched on.

2. All the tightening screws is fastened.

3. The working surrounding area is ensured to be dry and clean.

4. The shaft is lifted up using lifting chain attached to the shaft.

5. The experiment is carried out.

General shut-down procedure

1. Any liquid inside the tank is removed by opening the outlet valve

2. The tank is washed and rinsed to make sure no oil residue after the experiment.

3. The paddle/impeller inside the tank is removed and washed after use.

4. The power outlet is shut down.

6.1 Experiment 1

1. The tank is filled with water up to a depth of 30L.

2. Flat paddle is attached with the end of the shaft.

3. A small quantity of plastic pellet is added to the tank.

4. The speed of the impeller is turned up in small increments: 50 rpm, 100 rpm, 150m rpm and 200

rpm. The pellets are seen to swirl around in the water showing flow patterns.

5. The movement of the pellets and the flow pattern is observed and drawn.

6. The procedures are repeated by replacing the flat paddle with other impellers : turbine impeller

and screw propeller.

7. The procedures are also repeated with the baffles fitted in the tank with each flat paddle, turbine

impeller and screw propeller.

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6.2 Experiment 2

1. The tank filled with hydraulic oil up to a depth of 30 L

2. Flat paddle is attached with the end of the shaft.

3. The speed of the impeller is turned up to 50 rpm and the reading of force is recorded.

4. The speed is then turned up to 100 rpm, 150 rpm and 200 rpm with the force recorded at the

respective speed.

5. Step 3-4 is repeated with the baffles fitted in the tank.

6. The power consumed for each of the speed is calculated.

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7.0 Result

Experiment 1:

A) Water flow pattern without baffle inside the tank.

Types of impeller Flow pattern

Flat paddle

The water moves in circular motion (clockwise) with high velocity and created a deep whirlpool at the centre of the tank where the impeller is being inserted in.

Turbine impeller

The water moves in

circular motion (clockwise) with high velocity and creates a whirlpool at the centre of the tank where the impeller is being inserted in.

Table 1 shows the water flow pattern without baffle inside the tank.

Notes: All of the experiments were conducted using the same speed (100 rpm).

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B) Water flow pattern with baffle inside the tank.

Types of impeller Flow pattern

Flat paddle

The water circulates in an uneven clockwise

Moving in scatter with high velocity

Turbine impeller

The water circulates in an uneven circular motion with high velocity.

Table 2 shows the water flow pattern with baffle inside the tank.

Notes: All of the experiments were conducted using the same speed (100 rpm).

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Experiment 2:

A) Oil flow pattern without baffle inside the tank.

Types of impeller

Angular speed (rpm)

Angular speed, ω (rad/s)

Force (N) Torque (N.m)

Power (watts)

Turbine Impeller

100 10.47 0.00 0.00 0.00

200 20.94 3.64 0.4 8.38

300 31.42 18.18 2.0 62.84

400 41.89 31.82 3.5 146.62

Flat Paddle Impeller

100 10.47 24.55 2.7 28.27

200 20.94 60.91 6.7 140.30

300 31.42 88.18 9.7 304.77

400 41.89 145.45 16.0 670.24

Table 3 shows the results of different impeller without baffle when using oil.

10.47 20.94 31.42 41.890

100

200

300

400

500

600

700

800

Turbin propellerFlat paddle

Speed(rad/s)

Graph 1: Power against Speed without baffle by using oil.

B) Oil flow pattern with baffle inside the tank.

Types of Angular Angular Force (N) Torque Power

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Power (W)

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impeller speed (rpm) speed, ω (rad/s)

(N.m) (watts)

Turbine Impeller

100 10.47 0.00 0.00 0.00

200 20.94 17.27 1.9 39.79

300 31.42 40.91 4.5 141.39

400 41.89 81.82 9.0 377.01

Flat Paddle Impeller

100 10.47 72.73 8.0 83.76

200 20.94 122.73 13.5 282.69

300 31.42 177.27 19.5 612.69

400 41.89 240.91 26.5 1110.09

Table 4 shows the results of different impeller with baffle when using oil.

10.47 20.94 31.42 41.890

200

400

600

800

1000

1200

Turbin impellerFlat paddle

Speed (rad/s)

Graph 2: Power against Speed with baffle by using oil.

8.0 Calculations

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Power (W)

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A) For flat paddle without baffle when using oil at 100 rpm ;

Torque : 2.7 N.mTorque arm radius : 0.11 m

Angular speed (ω) = rpm x (2π / 60)

= 100 rpm x (2)(3.142) / 60

= 10.47 rad/s

Torque (T) = Force x radius

Force (F) = Torque / radius

= 2.7 N.m / 0.11 m

= 24.55 N

Power (W) = Torque (T) x Angular Speed ω (rad/s)

= 2.7N.m x 10.47 rad/s

= 28.27 W

9.0 Discussion

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This experiment consist of two parts which is experiment 1 and experiment 2 which has

different objectives. The objective of experiment 1 is to observe the flow patterns that be

achieved by the use of different impellers which are flat paddle impeller and turbine impeller

with and without the use of baffles. But, the objective of experiment 2 is to show how the power

consumed by a mixer varies with speed and the inclusion of baffle. Liquid mixing apparatus is

used to achieve these objectives.

In experiment 1, the flow patterns of water with different types of impeller are observed.

Four set of flow patterns are drawn with the use of two different impellers with and without the

baffle. These impellers used a rotor to increase the pressure and flow of a fluid and also act as the

agitator for mixing the substances. Agitation and swirling are the method for combining the

compounds. Based on the observation, we can know that flow pattern of the water is depend on

the type of impeller used. This experiment has been conducted using the same speed which is

100 rpm.

Therefore, we can see that the flow patterns produced are circular pattern and rotary motion

when using two types of impellers without the inclusion of baffles. Another observation that can

be seen is the production of the deep vortex in the without inclusion baffled tank. By using flat

paddle impeller, it created a deeper whirlpool than turbine impeller at the centre of the tank. With

the inclusion of baffle, the use of flat paddle and turbine blade as the impeller produced the same

flow pattern which is uneven. The flow is observed to have actually split into two streams which

are then continuing flowing along the tank wall and back to the impeller.

In experiment 2, two set of results are obtained in which the differences are the inclusion

of baffles. The torque is recorded at every increment of speed and the powers consumed and the

forces are calculated. The graph of power (W) against speed (rad/s) is also plotted to give a

clearer understanding of all of the relationships involved. From the results and the graph

obtained, it can be seen that the power consumed increases as the speed increases. It also can be

seen that the power consumed in a baffled tank is higher than without using baffled tank. This is

because with the use of baffles in an agitation process, vortex does not occur thus proper mixing

is achieved.

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The results obtained from this experiment are not exactly accurate. This is because

happened the errors occurred during conducting the experiment. Firstly, we should have repeated

the experiment for at least 3 times to get more accurate results. Besides that, the tank is not

cleaned thoroughly after conducting experiment. An unclean tank can affect the reading of the

torque because of the mixing of oil and water. Then, when the observation is being read non-

perpendicularly to the scale, it can cause parallax error during the measuring and filling the tank

with water and oil.

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10.0 Conclusion

From the data collected it shows that there is a difference for a tank with baffle and without

baffle. The fluid flow smoothly in circular pattern and rotary motion when baffle is not inserted

meanwhile when the baffle is inserted, the fluid flow unevenly and in random direction. This prove that

open non-scraping impellers favor gas dispersion even at low rotational speed, requiring a fairly low level

of energy consumption. Besides, it also shows that the shape and the diameter of the impeller affect the

speed of the rotation of impeller. In Experiment 1, the flat paddle impeller has the highest torque followed

by turbine impeller. This is why flat paddle impeller is being used widely in industries because it not

really slow and quite fast but do not consume much power. In other hands it is the most effective and

economical.While for the Experiment 2, the highest power obtained for either with or without baffle is

from the flat paddle impeller. These shows that, flat impellers have been described quantitatively in terms

of power consumption as the influence of highly shear-thinning behavior. Furthermore, high shear stress

at low power requirements both confirm that flat-bladed impellers could be valuable tools for dispersive

mixing in highly shear-thinning fluids, as they maintain a high shear rate level. In order to achieve higher

torque, use flat paddle with the baffle combination which will give more efficiency in handling more

workload fluid. Industrial mixing is a very important process because the quality of the final product will

be derived by that quality of the mix. If fluid mixing is not going to be done well, it will lead to a non-

homogenous products which lacks consistency, therefore when it comes to industrial phase, process of

mixing need to be design and selected carefully so that there are effective and efficient mixing

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11.0 Recommendations

1. To prevent any accident from happening, seal the impeller at the end of the shaft and also seal to

the tank properly.

2. For each impeller, attached them to the base of the bush level carefully so that it will not get off

during the experiment.

3. Wear gloves to avoid leaking of oil and easier to do a job when handling the experiment.

4. The eyes must be perpendicular to the reading scale to avoid parallax error.

5. Carefully lift the lid as it involved the heavy set of tank and engine.

6. Handle the oil properly so that no spilling on the floor as it will become slippery and can lead to

serious injury

7. The tank should be cleaned thoroughly after conducting the experiment with an oil to prevent

high concentration of oil to be attached at the wall of the tank besides preventing the oil and

water from mixing.

8. The experiment should be repeated at least 3 times to obtain average and more accurate results.

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12.0 References

1. Thermofluids Laboratory Manual, Fluid Mixing Experiment.

2. https:// en.wikipedia.org/wiki/mixing/process engineering

3. http://www.aiche.org/academy/courses/ch090/industrial-fluid -mixing

4. Frank M.W, Fluid Mechanics ninth edition, McGraw-Hill.2005

5. http:/www.craneengineering.net/products/mixers/documents/

craneEngineeringprinciplesoffluidmixing.pdf

6. http://ceb.dlut.edu.cn/uploads/soft/110415/7-110415153545.pdf

7. http://www.ginhong.com/articles/the-importance-of-industrial-mixing/

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13.0 Appendices

Flat paddle without baffle

Turbine impeller without baffle

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Flat paddle with baffle

Turbine impeller with baffle

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