160a lab manual-student s2015.pdf

CHEMICAL ENGINEERING 160A ENVIRONMENTAL ENGINEERING 160A Chemical & Environmental Engineering Laboratory I

Laboratory Manual

Edition

2015

DEPARTMENT OF CHEMICAL & ENVIRONMENTAL ENGINEERING BOURNS COLLEGE OF ENGINEERING UNIVERSITY OF CALIFORNIA, RIVERSIDE

C H E M I C A L A N D E N V I R O N M E N T A L E N G I N E E R I N G L A B O R A T O R Y I

Laboratory Manual

© UC Riverside, 2015 Bourns College of Engineering

Department of Chemical and Environmental Engineering Riverside, CA 92521

Table of Contents

C H A P T E R 1

Introduction 1

Laboratory Exercises, Organization,

and Scheduling 2

Laboratory Preparation 3

Personnel 4

C H A P T E R 2

Laboratory Conduct 5

General Rules 6

Care and Use of Laboratory Equipment 7

Care and Use of Chemical Reagents 9

C H A P T E R 3

Data Analysis, General Considerations 11

Sources of Errors 12

Uncertainty Analysis 13

Statistical Analysis of Data 14

Graphical Analysis 15

C H A P T E R 4

Experiment #1 – Drag Coefficient 18

Experiment #2 - Gas Diffusion 20

Experiment #3 - Aeration 24

Experiment #4 – Ion diffusion 26

Experiment #5 - Wetted Wall 29

Experiment #6 - Pipe friction and fittings

headloss 32

I N T R O D U C T I O N

1

INTRODUCTION

What is the purpose of Chemical and Environmental Engineering Laboratory I?

he course, Chemical and Environmental Engineering Laboratory I, CHE & ENVE 160A, is the first in a series of three laboratory courses required of all Chemical Engineering and Environmental Engineering majors. The goals of these courses are to: 1) reinforce concepts learned in previously taken lecture

courses, 2) provide students with hands-on experience in collecting design and operating data from engineering systems, 3) begin to challenge students in planning and conducting experiments to obtain relevant data needed for proper design and operation of chemical and environmental engineering systems, and 4) give students an opportunity to practice and improve their technical writing and oral presentation skills.

To avoid crowded lab conditions and give each student as much hands-on experience as possible, each lab section is limited to 25 students. Students will work in groups of four or five. Groups will stay together throughout the quarter. It is important that the members of the group work together to develop laboratory protocols, complete the laboratory exercises, and submit written reports in a time efficient manner. Each group MUST review the laboratory manual and develop a laboratory protocol together prior to doing the lab work, and determine work tasks before conducting the lab. During each session each student should record the experimental data in her/his laboratory notebook.

There are six scheduled hours per week for this class. However, for the weeks your group is in laboratory, only two to three hours will actually be spent in the laboratory collecting data. The additional time each week is provided for lab groups to meet together to discuss upcoming laboratory exercises, visit the laboratory to become acquainted with each laboratory module, to work on pre-labs and protocol development and/or to work on data analysis and lab write-ups. EXTREMELY IMPORTANT SUGGESTION: TAKE ADVANTAGE OF THIS ADDITIONAL TIME - DO NOT WASTE IT!

For the Spring 2014 Quarter, there are two lab sections. Section 1 labs will be conducted Monday and Wednesday, 9:10 am to 12:00 pm. Section 2 labs will be

Chapter

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L A B O R A T O R Y S A F E T Y A N D P R O T O C O L

2

conducted Wednesday and Friday, 12:10 pm to 3:00 pm. The lab period for which your group is not scheduled will be used for your regular lab group meeting. Laboratory exercises will begin on the week of April 7th.

Laboratory Exercises, Organization, and

Scheduling There are a total of five different laboratory exercises for CHE/ENVE 160A. The four labs will be conducted over 10 weeks. There are extra weeks available for oral presentations and lectures.

The four laboratory exercises are: Lab no. Topic

1 Drag coefficient 2 Arnold Cell/Gas

diffusion 3 Aeration 4 Ion diffusion 5 Wetted Wall 6 Pipe friction and

fittings (headloss)

As noted previously, there will be four or five students per lab group. Unless a student withdraws from the class, the composition of each lab group will remain fixed for the entire quarter. During the first week of the quarter, groups will be determined and assigned a number.

If difficulties arise within a group, please communicate them to Prof. Wheeldon or Prof. Yan. REMEMBER, HOWEVER, AN IMPORTANT CHARACTERISTIC THAT EMPLOYERS ASK ABOUT IS HOW WELL A PROSPECTIVE EMPLOYEE CAN WORK AS A MEMBER OF A TEAM. In a company you will not be able to pick the people you work with. You must be able to overcome personal idiosyncrasies to get the job done - period.

The general laboratory schedule will be:

Week No. Task 1 Introduction, Lab Training 2 Laboratory Rotation #1 3 Laboratory Rotation #2 4 Laboratory Rotation #3 5 Oral Presentation #1 6 Statistical Analysis Lecture 7 Laboratory Rotation #4 8 Laboratory Rotation #5


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9 Laboratory Rotation #6 10 Oral Presentation #2

The specific schedule for each lab group is as follows:

Rotation Module 1 Drag coeff.

Module 2 Arnold Cell

Module 3 Aeration kLa

Module 4 Ion diffusion

Module 5 Wetted Wall

Module 6 Pipe Flow

1 A, G B, H C, I D, J E, K F, L 2 F, L A, G B, H C, I D, J E, K 3 E, K F, L A, G B, H C, I D, J 4 D, J E, K F, L A, G B, H C, I 5 C, I D, J E, K F, L A, G B, H 6 B, H C, I D, J E, K F, L A, G

When you find out what your lab group number is - write it down here.

MY LAB GROUP NUMBER IS ________.

Laboratory Preparation Laboratory notebook. Prelabs, notes and data should be recorded with an ink pen

in a permanently bound laboratory notebook. The most useful notebook is one

that has pages that makes graphing easy. Students should purchase one before

the beginning of the first exercise and use the same notebook for each experiment. You must have a lab notebook that creates carbon copies of each page. Record pre-experiment notes and protocols, changes from standard

procedures made during the course of the experiment, data, preliminary data

analysis and plots (for example, checks of a calibration curve to make sure an

instrument is operating correctly), and any other observations that you may feel

are interesting and noteworthy.

Why is it important to record information in a permanently bound notebook? Loose papers and pages in spiral bound notebooks are easily lost. Further, a

permanently bound notebook is a journal of your in the laboratory. Journals are extremely important when legal issues such as patents and lawsuits come about.

The time and activities associated with the experiment are entered sequentially.

Thus, there can be no question of whether information was “added” at a time

other than when the experiment was conducted and that the information was

indeed collected from the experiment and not another source.


4

Each laboratory session requires considerable preparation. Students are required to develop their own protocols for conducting experiments in CHE/ENVE 160A. The information about each module in Chapter 4 of this manual is intended only to introduce the students to the apparatus they will use to collect data necessary to complete experimental objectives. EXPERIMENTAL PROTOCOLS ARE NOT PROVIDED. It is each group’s responsibility to visit the lab during an appropriate class session prior to conducting each laboratory in order to inspect the apparatus and become acquainted with its operation. Each group will then be required to draft a protocol that must be approved by the TA’s or Prof. Wheeldon/Prof. Yan before conducting the laboratory at the scheduled time.

Thus, students are required to be very familiar with the instrumentation and have developed all procedures before coming to the lab session and should have her/his laboratory notebook ready to enter data at the start of each lab period. LAB PROTOCOLS AND ALL COLLECTED DATA SHOULD BE RECORDED IN A BOUND LABORATORY NOTEBOOOK WITH SEQUENTIALLY NUMBERED PAGES. Never use loose or scrap pieces of paper. Note, the TAs will not be responsible for providing data for the experiments or making sure students have collected all of the necessary data.

Prior to each laboratory session, the laboratory manager (Kathy Cocker) and TAs will generally check that all of the equipment is in good working order and they will make sure that all necessary gases and/or solutions are available for the labs. However, other than ensuring that the students carrying out the lab exercises in a safe manner, the TAs will be there primarily to answer questions, not run the instruments for the lab exercise.

Personnel Class Instructor: The professor for the class are:

Session 1: Dr. Ian Wheeldon. His office is in B319, his phone is (951) 827-2471, and his email address is [email protected].

Session 2: Dr. Ruoxue Yan. Her office is in A247, her phone is (951) 827-2242, and her email address is [email protected].

Laboratory Manager

The Chemical & Environmental Engineering Laboratory Manager is Kathy Cocker. His office is in B307 Bourns Hall and the phone number is (951) 827-2097.

Laboratory Instructors

Peter Byrley Email: [email protected] Tung Pham Email: [email protected]


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6

LABORATORY SAFETY AND PROTOCOL

What to do and what not to do—above all use common sense!

The Chemical and Environmental Engineering Programs are privileged to have excellent teaching and research laboratories in Bourns Hall. Rooms B108, B121, and B134 are the principal wet-lab teaching laboratories. B314, B316, B318, B328, B328A, B350 and B334 are the research laboratories areas. The general research topics and faculty responsible for the research labs are as follows:

• B312 Bourns - General biochemical engineering support and analytical instrumentation

• B314 Bourns - Biosensors - Dr. Ashok Mulchandani

• B318 Bourns – Biological Processes in Environmental Engineering - Dr. Mark Matsumoto

• B328 Bourns - Soil/hazardous organic contaminant interaction - Dr. Mark Matsumoto; Bacterial adhesion laboratory - Dr. Sharon Walter;

• B350 Bourns-Nano electrochemical system laboratory – Dr. Nosang V. Myung

• B334 Bourns - Cold room (general support)

If you are interested in working in any of these areas or with any of these faculty members, students are encouraged to contact the various faculty members.

LABORATORY CONDUCT Proper conduct of everyone in the laboratories is important not only for the efficient and congenial operation of the labs, but also for the safety of all involved. This

Chapter

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conduct applies to ALL STUDENTS - undergraduate, graduate, and postdoctoral. In addition to these guidelines, STUDENTS WORKING AS AN EMPLOYEE IN A RESEARCH LAB MUST ATTEND A GENERAL SAFETY ORIENTATION FOR LABORATORY PERSONNEL GIVEN BY THE CAMPUS ENVIRONMENTAL HEALTH AND SAFETY GROUP! This is a state and federal regulation. A faculty supervisor or the Laboratory Manager (Kathy Cocker) can sign you up for one of these regularly offered sessions.

General Rules

Clothing and shoes: Always wear closed shoes in the laboratory. Open toe sandals are not adequate protection from chemical spills. Spills and accidents can (and do) happen. Students should wear clothes that they are worried about damaging and/or purchase a lab coat when working in the labs. Clothing is readily damaged as a result of chemical spillage and splashing, particularly from strong acids, bases, and redox chemicals. As an added precaution students should wear a chemical resistant apron when handling strong acid/base/solvent chemicals.

Safety Goggles: CHEMICAL SAFETY GLASSES OR GOGGLES MUST BE WORN AT ALL TIMES IN THE LABORATORY. If you wear eyeglasses, they should have splash shields to protect against chemical splashing. Regular eyeglasses, by themselves, are not adequate protection against chemical splashing. Also, certain chemicals may ruin plastic lenses. It is recommended that students purchase a pair of chemical safety glasses/goggles from the bookstore and reserve them for their personal use when working in the laboratories.

Eyewash stations and showers: There is a flexible eyewash/shower hose located at all sinks in the teaching and research laboratories. In addition, drench showers are located in several of the research labs. Familiarize yourself with the location and use of these safety items.

Eating and Smoking: Eating, drinking or smoking is not permitted in any of the laboratories.

Animals and Pets: Animals and pets are not permitted in any of the laboratories.

Refrigerator and Ovens: Refrigerators, incubators, and ovens located in the laboratories are not to be used for storing or preparing food.

Flames: Open flames should be placed in a fume hood if possible and always on a non-flammable surface away from combustible material. Never leave open flames unattended in the lab.

Please read these rules thoroughly.

They are very

important in

ensuring that

students have a

safe lab experience.


8

Chemical Spills: Small spills should first be neutralized: sodium borate for base spills and sodium bicarbonate for acid spills. After neutralizing mop or sponge up spills immediately. Large spills should first be contained with an absorbent material such as vermiculite and then neutralized. Additional absorbent may then be added to take up the neutralized liquid and picked up. A faculty member or the Laboratory Manager, and Environmental Health and Safety (25528) should be notified when a large spill occurs.

Volatile Organics: A fume hood should be used when using or dispensing a volatile organic reagent. If the reagent is to be regularly used or dispensed for a project, as additional protection, an appropriate respirator should be purchased, fitted, used, and regularly maintained. Respirators should not be shared; they are to be purchased, fitted, used, and maintained by one person. Environmental Health and Safety will fit and test respirators free of charge.

Pipetting: NEVER pipet any solutions by mouth. Pipet with a pipet bulb or a pipettor. After using any pipet, please place it in a pipet storer for subsequent washing in a pipet washer.

Gas cylinders: Pressurized gas cylinders should be strapped or chained to a bench top or wall. Before moving cylinders always remove regulators and screw on the cap. DO NOT attempt to change regulators without prior training. Depending on the gas type, regulator threading and connections vary to prevent mixing of incompatible materials. Empty gas cylinders should be returned to the supplier as soon as possible.

Chemical waste disposal: Chemical wastes, spent and old reagents, and effluents from bench-scale reactor systems SHOULD NOT BE DISPOSED INTO THE FLOOR DRAINS OR SINKS! Before beginning your laboratory experiment, check with a faculty member of the Laboratory Manager regarding proper disposal of expected wastes. Environmental Health and Safety will collect and dispose of hazardous wastes upon request.

Daily departure: Check your work area when you leave for the day to be sure everything is clean and neat. If you are the last person in the room, check all sinks in the room to make sure the tap water is turned off. Make a cursory glance around the remainder of the laboratory to see if there are any major problems. If you are the last one to leave for the day, please check each lab to see that all tap water is off, that there are no major problems, and that all doors are locked. As you leave the laboratory TURN OFF THE LIGHTS AND LOCK THE DOORS.


9

CARE AND USE OF LABORATORY EQUIPMENT

Many of the analytical instruments and much of the laboratory equipment in the Chemical and Environmental Engineering Laboratories are commonly used for both teaching and research. Therefore, it is imperative that each student use and maintain instruments and equipment properly.

BEFORE USING ANY ANALYTICAL INSTRUMENT

Read the instruction manual or obtain training by qualified personnel on the use, care, and maintenance of the instrument. Please contact the Laboratory Manager regarding instruction manuals or training.

Failure to use and maintain instruments properly will lead to poor laboratory results and jeopardize the progress of important research projects. Students who use and maintain of laboratory instruments and equipment improperly may be subject to disciplinary action.

From time to time, students may experience problems when using some of the analytical instruments. When problems occur, they should be discussed with the Laboratory Manager. DO NOT ATTEMPT TO "FIX" THE INSTRUMENTS WITHOUT CONSULTING WITH A FACULTY MEMBER OR THE LABORATORY MANAGER.

Balances: Balances and their surrounding areas should be cleaned using a brush after each use. Residual traces of reagents, liquids, etc. should not be evident. The experiment of the next person using the balance may be ruined by your laziness and lack of consideration.

pH Meters: pH meters are available in various laboratory rooms. They are not to be moved from the room without permission from the Laboratory Manager or faculty member. The pH probes should not be used in harsh solutions or solutions that may foul the probe. After use, the probes should be rinsed and placed in a neutral buffer solution for storage; pH meters should be placed in a “stand-by” mode.

Ovens and Furnaces: Convection ovens are primarily for reagent desiccating and solids/moisture analyses, and are typically set at around 100 to 110oC. Muffle furnaces are primarily used for volatile solids analyses and are set at around 550oC. Do not adjust the temperatures of ovens or furnaces without consulting with the other users.

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Autoclaves: In addition to small autoclaves located in several of the research laboratories, a large autoclave for sterilizing glassware and culture media is located in B358 Bourns Hall. Students needing to use this autoclave should consult with the Laboratory Manager before use.

Fume hoods: The Chemical and Environmental Engineering Laboratories contain two types of fume hoods: canopy (elephant trunk) and sash. Sash-type fume hoods are to be used for making up strong acid/base reagents, dispensing volatile chemicals, and performing digestions and extractions. When using sash-type fume hoods, the glass screen should be lowered at all times, except when placing equipment and or chemicals inside. Always prepare reagents with the glass screen lowered, wearing goggles at all times. DO NOT STORE EQUIPMENT, CHEMICALS OR REAGENTS IN SASH-TYPE FUME HOODS. Canopy fume hoods are to be used when hazardous volatile vapors may be emitted from a bench-scale laboratory experiments that runs for long periods of time.

Dishwashers: There are various laboratory dishwashers located in the labs to be used for glassware cleaning. Instructions for their use can be obtained from the Laboratory Manager. Often, however, glassware will need to be washed by hand. When washing glassware, etc. by hand always wear goggles and gloves. You may not know what residual chemicals may be present in dirty glassware. Do not store dirty glassware around the sinks. Wash them first before leaving them to dry around the sink. This will prevent an accident occurring when someone else picks up the glassware.

WHEN USING CHROMIC ACID OR OTHER DILUTE ACID SOLUTIONS TO WASH GLASSWARE, BE SURE TO CLEAN THE SINKS, FLOORS, AND SURROUNDING AREAS THOROUGHLY. YOU MAY CAUSE THE NEXT PERSON TO HAVE SERIOUS BURNS AS A RESULT OF YOUR NEGLIGENCE!

Borrowing: Environmental Engineering laboratory instruments and large equipment should not be moved from room to room. If there is a need to do so for your research, obtain permission from a faculty member or the Laboratory Manager. EQUIPMENT OR SUPPLIES OF ANY KIND MAY NOT BE BORROWED OR REMOVED FROM THE LABORATORIES FOR USE BY OTHER DEPARTMENTS WITHOUT FIRST FILLING OUT A DEPARTMENTAL EQUIPMENT LOAN FORM. SEE THE LABORATORY MANAGER FOR PERMISSION AND THE NECESSARY FORMS. DO NOT LOAN EQUIPMENT OR SUPPLIES TO NON-CHEMICAL/ENVIRONMENTAL ENGINEERING FACULTY OR STUDENTS WITHOUT CONSULTING WITH THE LABORATORY MANAGER.


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CARE AND USE OF CHEMICAL REAGENTS

Dry chemicals are separated generally into two categories: organic chemicals and inorganic chemicals. Strong liquid acids and bases are stored separately in cabinets under fume hoods. Volatile liquids are stored in cabinets which have exhaust vent built in to carry away any off-gases.

Labeling: When new reagents are received, either for general lab use or for a specific project, mark each bottle or jar of chemical with the month and year received, and your initials (e.g. Rec'd 10/96 MRM). Also mark the bottle or jar when the chemical is first opened (e.g. Open 12/96 MRM). Use labeling tape (not masking tape) or adhesive label. Grease pencil, or other non-permanent marker, is not acceptable; labeling information is easily erased.

Dispensing: When weighing reagents, use an intermediate container. Carefully dispense the approximate amount of reagent you'll need into the intermediate container first, then transfer the reagent onto the weighing vessel or paper in the balance. Do not return excess chemical (in the intermediate container) back into the reagent bottles.

Strong Acids and Bases: Liquid acids and bases should be dispensed in a sash-type fume hood. Carry acid/base bottles in the rubber acid/base carrier, or use a cart. Never carry acid/base bottles by the handle or neck. When holding an acid/base bottle, always have one hand under the base of the bottle. Wear goggles, apron and gloves when dispensing and mixing strong acids or bases. Mix strong acids or bases in a Pyrex or Kimax flask or beaker. Ordinary flint glass reagent bottles will crack from the heat. Add the acid or base to water in small incremental amounts over time. ALWAYS add concentrated acids or bases to water. NEVER add water to concentration acids or strong bases !!

Storage and Labeling of Reagent Solutions: Reagent solutions should be prepared using volumetric flasks or graduated cylinders. However, solutions should NOT be stored in them. After a reagent solution is made, it should be placed in a clean, appropriately sized reagent bottle. The reagent bottle should then be labeled with the following information: contents, date of preparation, preparer's initials, project, disposal date (date beyond which reagent should be discarded), and other special warnings (e.g. flammable, volatile, extremely caustic, etc.). An example is: 0.1 M NaOH, MRM, Prep. 11/1/96, Dis. after 2/1/97. Improperly marked reagents must be assumed to be “old” and will be discarded.

Water: There are three kinds of water available in our laboratories:

Tap water: Water at the sinks is regular water from the municipal water supply. However, because there are many chemicals in use and the possibility of backflushing

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exists, all of the taps are marked, “Industrial Water - Do Not Drink”. If you want drinking water, please use the drinking fountains near the lavatories.

Reverse osmosis (RO) water - This water is available from the special taps marked “DI” at each sink. This water is very high quality and is adequate for most reagent purposes.

Nanopure water - This water is made by taking RO water and passing it through activated carbon, two mixed bed ion exchange columns, and a 0.2 micron filter. This water is the highest quality water available in the Chemical and Environmental Engineering laboratories, and should be used sparingly, for mixing high purity reagents and standards, and for final rinsing of special glassware.

D A T A A N A L Y S I S B A S I C S

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DATA ANALYSIS BASICS

Some form of analysis is required on experimental data. The analysis may be a very simple qualitative assessment about an observed trend or it may involve complex error analysis coupled with a statistical analysis to determine the probability of true differences between experimental data sets.

While the ability to carry out experiments and collect data is important, the usefulness of conducting experiments depends on careful analysis of the collected data. Without analysis, an experiment is merely a work task. Data analysis can be used for a variety of purpose such as determining 1) whether collected data are reasonable, 2) the uncertainty associated with the measurements, 3) coefficients for theoretical models such as KLa, 4) whether significant differences in data sets exist as a result of changed operating conditions, and 4) empirical mathematical models for relationships between different parameters. However, the analysis of experimental data is an acquired skill that improves (hopefully) with experience. One of the purposes for this course is that students begin to develop these skills.

General Considerations A good outline that can be used for experimental data analysis has been developed by Holman1 (1994).

1. Examine data for consistency. Are the measurements reasonable? This basic question is the common sense approach to experiments. A simple example is when you fill up your car with gasoline, you expect your gas gage to read “Full” right after. If it doesn’t, you suspect something is wrong like the gage is broken, your gasoline tank leaked, or the pump wasn’t working correctly.

This same logic applies to engineering experiments. When you bubble pure oxygen gas through water that is not saturated with oxygen, you would expect that dissolved oxygen concentration to increase, not decrease or stay the same. Why do you know this? Based on mass transfer considerations (of course!).

1 Holman, J.P. Experimental Methods for Engineers, 6th ed., McGraw-Hill, Inc., San Francisco, 1994.

Chapter

3

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To use this common sense approach it is important that the experimenter be familiar with the expected trends/readings based on theory and/or past experience. You don’t want to continue doing an experiment if you are collecting “bad” data. If you know beforehand what to expect, this type of situation can be avoided. The more thorough the understanding of what is expected based on theory and/or experience prior to the start of an experiment, the more likely it is that the experiment will be successful.

2. Perform a statistical analysis of data where appropriate. When measurements are repeated several times, statistical parameters such as mean, median, and standard deviation are useful in evaluating the level of precision for a particular measurement, and level of confidence for a given data set.

3. Estimate uncertainties in the results. All instruments that measure something have an uncertainty associated with them. For example, when a thermometer reads 100oC, is it accurate to 1oC or 0.1oC. If the temperature reading is used in conjunction for another parameter such as heat content, then the temperature uncertainty carries over to heat content as well. Generally, these types of uncertainties can be estimated before the experiment is conducted.

4. Anticipate results from theory. The theory or theories relevant to the experiment subject should be carefully reviewed to determine what trends may be expected before the experiment takes place. This step is particularly important in determining an appropriate graphical presentation of the experimental data. For example, if a first-order system is subjected to a step input, a semilog plot of the data should result in a linear plot. Use of dimensionless parameters (e.g. Reynolds number, Peclet number) may also provide important insights.

5. Correlate the data. The experimental data should be interpreted in terms of physical theories or the basis of previous experimental work (done by others). The results should be examined to see if they conform to or differ from previous investigations or standards.

Sources of Errors Errors occur in all experiments. Some of the errors can be avoided while others cannot. Most of the errors that can be avoided are due to uncontrollable variables, and/or lack of experience or carelessness on the part of the experimenter. These types of errors can be avoided by carefully reviewing each step and condition (variable) in an experiment and assessing whether they can significantly affect the outcome of the experiment. If so, then the experimenter should alter the experiment, or pay particular attention to certain aspects of the experiment, to ensure that a gross error does not occur. As the saying goes, “An ounce of prevention is worth a pound of cure.” This


15

means that time spent preparing an experiment is well worth the effort. A great deal of time and money can be wasted as the result of poor planning.

Beyond these controllable errors, there are errors of “uncertainty”. These are errors that are beyond the control of the experimenter. There are two principal uncertainty errors, fixed and random. Fixed, systematic, or bias errors are errors that are generated repeatedly by the same amount for an unknown reason. For example, a ruler used to measure length indicates a length of 1 m. However, the ruler actually measures 0.99 m when compared to the actual standardized 1 m length. Thus, the ruler always measures 1 cm short per m measurement. These types of errors are often unknown. Calibration of an instrument to an absolute standard, such as National Bureau of Standards (NBS) standards, is the best way to detect and/or avoid systematic errors.

The second type of uncertainty errors is random errors. These errors are caused by a variety of reasons that cannot be avoided such as experimentalist bias, fluctuations in instrument readings, minor temporal variations in variables, etc. Every measurement has a random uncertainty associated with it. This uncertainty is often related to the accuracy of the instrument. For example, a pH probe may have an accuracy of ±0.01 pH units within the pH range between 2 and 12. This means that, properly calibrated, that this particular pH probe is accurate to within 0.01 pH unit between pH 2 and pH 12. Outside of those pH ranges, the pH probe’s accuracy may or may not fall within that specification.

Uncertainty (Error) Analysis Whenever a measurement is made there always is some uncertainty. The instrument manufacturer may define this uncertainty, or may be estimated by the experimenter (based on experience). Whatever the case, these measurement uncertainties are carried on when a calculated result is generated. Many measurement uncertainties may be associated with a single calculated result. The overall uncertainty for the calculated result is a function of the error associated with each measurement. In general, this overall uncertainty can be calculated as:

21

22

22

2

11 ⎥

⎥⎦

⎤

⎢⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛

∂

∂++⎟⎟

⎠

⎞⎜⎜⎝

⎛

∂

∂+⎟⎟

⎠

⎞⎜⎜⎝

⎛

∂

∂= n

nT e

xRe

xRe

xRE …

where R = function of the independent (measured) variables, xi = independent (measured) variable i, ei = uncertainty in measured variable i, and ET = overall uncertainty in calculated function R.

As a simple example, consider the volume of a rectangular box that is determined by measuring its dimensions with a ruler that has an accuracy of ±0.2 cm. The measured


16

dimensions are L = 45 cm, W = 60 cm, and H = 20 cm. Based on these measurements, volume would be 54,000 cm3.

To determine the uncertainty of the volume:

( )

( )

( ) 2

2

2

700,24560

9002045

200,12060

cmLWHV

cmLHWV

cmWHLVLWHV

===∂

∂

===∂

∂

===∂

∂

=

( )( )[ ] ( )( )[ ] ( )( )[ ]( )3

21

222222

620

2.0700,22.09002.0200,1

cmcmcmcmcmcmcmET

±=

++=

Statistical Analysis of Data The purpose of this section is to not to provide a comprehensive overview of statistical data analysis, but rather to review important concepts and outline appropriate application of statistics to experimental data. Most of this information has been covered in previous courses. More in depth coverage of statistical data analysis can be obtained from course work or various textbooks.

Population Statistics

When a set of repeated measurements is made, the individual readings will vary from each other. Most often statistical measures are used to describe the entire set of measurements in terms of a centralized number, the spread of the data, and frequency of distribution. Typical parameters include:

Arithmetic mean (or average) - ∑=

=n

iixn

x1

1

Median - middle data point of a sequentially ordered data set. The datum for which half of the data points in the set are higher and half are lower in value is the median.


17

Standard deviation - descriptor of the spread of the data compared to the mean =

( )21

1

2

1⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢

⎣

⎡

−

−=∑=

n

xxn

ii

σ

Confidence interval - the probability that the actual mean value lies within a certain number of σ values around an experimental mean. As an example, if a measured flow reading has a mean of 100 and a standard deviation of 5, the 95% confidence interval would be 100 ± 1.96(5) = 100 ± 9.8. In other words, there is a 95% probability that the actual mean value is between 90.2 and 109.8.

Chauvenet’s criterion - sometimes one or two data points seem to be very different compared to all of the other data points in a population. While it is logical to throw out these types of data points, it is possible to apply a statistical test, Chauvenet’s criterion, to determine whether data may be discarded. To apply this criterion, the deviation of each data point from the mean must be calculated and divided by the standard deviation: ( ) σ/xxi − . The calculated value is compared to Chauvenet’s criterion, which is a function of the number of readings in the population.

Number of total readings 3 4 5 6 7 10 15 25 50 100

Max. deviation, ( ) σ/maxxxi −

1.38 1.54 1.65 1.73 1.80 1.96 2.13 2.33 2.57 2.81

Graphical Analysis Experimental scientists and engineers are well known for the use of graphs to highlight certain data trends and insights. However, random graphing of data usually generates an excess of charts that are useless. Considerable thought must be given to the physical phenomena involved in each experiment before preparing a plot. The person who understands the physical processes (the theory) is usually the person who can most successfully present experimental data graphically.

The most common graphical technique is the correlative graph in which the relationship between two variables is plotted in a linear manner. To do this, the experimenter must know what type of function will best describe the data. This knowledge is based on theoretical understanding of physical phenomena.

A summary of plotting methods for various functions to obtain straight lines.


18

Function Plotting Method Slope Y-intercept baxy += y vs. x on linear paper A b

baxy = log y vs. log x on log-log paper B log a bxaey = log y vs. x on semilog paper b log e log a

bxaxy+

= y1 vs.

x1 on linear paper A b

2cxbxay ++= 1

1

xxyy

−

− vs. x on linear paper C b + cx1

cbxaxy ++

= 1

1

yyxx

−

− vs. x on linear paper 1

2

xabb + a + bx1

2csbxaey += ( )

⎥⎥

⎦

⎤

⎢⎢

⎣

⎡

⎟⎟⎠

⎞⎜⎜⎝

⎛− 11

1

logxx

yy vs. x on semilog

paper

c log e b + cx1 log e

bxey −−=1 ⎟⎟⎠

⎞⎜⎜⎝

⎛

− y11log vs. x on semilog

paper

B

xbay += y vs. 1/x on linear paper B a

xbay += y vs x on linear paper B a

The best method to determine the slope and y-intercepts for these various plots is the use of the least squares method of linear regression, which is found in many standard plotting software packages such as Excel.

L A B O R A T O R Y E X E R C I S E S

19

LABORATORY EXERCISES

This chapter provides an introduction for the laboratory exercises that CHE/ENVE 160A students will be conducting during this course.

As noted previously, there are a total of four different laboratory exercises for CHE/ENVE 160A. The four labs will be conducted by each group over the duration of the 10 week quarter. The four laboratory exercises are:

Lab No. Topic 1 Drag coefficient 2 Arnold Cell/Gas

diffusion 3 Aeration kLa 4 Ion diffusion 5 Wetted wall column 6 Pipe Flow and Fitting

Headloss

To reiterate there will be four or five students per lab group. Groups are required to review the relevant sections in this chapter prior to conducting each laboratory exercise. This information is intended to assist each group in generating an appropriate pre-lab and experimental protocol that they can use during their assigned laboratory session to achieve all experimental objectives.

Chapter

4

1

L A B O R A T O R Y E X P E R I M E N T

20

Exercise #1 – Drag Coefficients of

Particles Experimental Objectives Please design and conduct experiments to achieve both of the following objectives

1) Determine the relationship between drag coefficient and Reynolds number for spherical particles. Compare you results to Stokes Law where CD = 24/Re.

2) Demonstrate the effect of particle shape on the velocity of a sphere and a streamlined shape in a viscous fluid.

Experimental Apparatus Experimental apparatus consists of two liquid filled tubes shown Figure 4.1 below. The particle of interest is dropped into one of the columns and the time required travel a predefined distance is recorded. It is suggested that glycerol and castor oil are used. The spheres and variously shaped particles are to be dropped ONE AT A TIME from the top of the tubes. When each particles arrives at the recess in the base of the tubes, it is removed by turning the valve through 180°. It is importantly to remove each sphere as it reaches the valve, as two or more spheres will prevent the valve from operating.

Figure 4.1 Schematic of drag coefficient apparatus.

Background

The drag force exerted on a solid object moving through a fluid is commonly considered as being made up of two components— Surface Drag and Form Drag. The total drag force can be expressed as,


21

€

F = CDAρV 2

2

Stokes Law can be used to determine the viscosity of a fluid using the following equation.

€

µ =29γ s1 − γ s2( )

VR2

In the case of surface drag around a sphere, it has been shown that the drag coefficient is related to the Reynolds number (Re) as follows:

€

CD =24Re

And, that the drag coefficient of spherical particles can be determined experimentally by,

€

CD =83

r γ s − γ f( )ρV 2

Notation:

F, drag force (N); CD, drag coefficient; A, cross-sectional area of solid object (m2); ρ, fluid density (kg m3); V, relative velocity of sphere through fluid (m s-1); µ, coefficient of dynamic viscosity (N s m-2); γs, specific weight of solid object (N m-3); γf specific weight of fluid (N m-3); r, radius of sphere (m); D, diameter of sphere (m); Re, Reynolds number of a solid object; g, gravitational acceleration; M, mass of solid object

γglycerol=1.046 g cm-3; γCaster oil=0.95 g cm-3; γwater=1 g cm-3

γ= Mg/Volume

Suggested Discussion Questions to Address in the Laboratory Report Discuss the relative contributions of surface and from drag when particles of various shapes are dropped in a viscous fluid. In this case, which is dominant? When would you expect a streamlined shape to travel faster than the spheres?


22

Exercise #2 - Gas Diffusion Experimental Objectives The design and operation of process plants to achieve the desired changes in materials depends upon the properties of the materials (or contaminants) in a flowing medium (gas or liquid). One of the most important properties of materials in fluids under such circumstances is diffusivity. Fluid flow and mass transfer operations depend to some extent on this property and such data are always needed in plant design.

The objective for this laboratory exercise is to determine the diffusivity of a volatile fluid in air using an Arnold cell. Please design and conduct experiment to achieve the following objectives

1) determine the gas phase diffusion coefficient of acetone in air at 40 C.

2) compare the diffusion coefficient obtained from experimental data with published data from a handbook.

Theory The diffusivity of the vapor of acetone in air can be determined by Winklemann’s method in which liquid is contained at constant temperature in a narrow diameter vertical tube, which an air stream is passed over the top of the tube. This technique ensures that the partial pressure of the vapor is transferred from the surface of the liquid to the air stream by molecular diffusion.

As outlined in the text:

( )zBzAAA

ABzA NNydzdycDN ,,, ++−=

where =zAN , constant molar flux of A (sm

kmolw ⋅

), ABD = diffusivity of acetone in air ( sm2

), c =total molar concentration in the gas phase ( 3mkmol ),

dzdyA = change of the mole

fraction of A along the diffusion path, yA = mole fraction of component A in the vapor phase, zBN , = molar flux of B

However, the net flux of B is zero throughout the diffusion path. Therefore,

dzdy

ycDN A

A

ABzA −

−=1,


23

The above equation may be integrated from z = z1 to z = z2 and from yA = yA1 to yA = yA2 which yields:

( )

( )( )

( )lmB

AAAB

A

AABzA

yyy

LcD

yy

zzcDN

,

21

1

2

12, 1

1ln

−=

−

−

−=

where lmBy , = log-mean average concentration of component B and L = length of the diffusion path (m).

Under pseudo-steady-state conditions, the molar flux xAN , may also be described by:

dtdz

MN

A

LAzA

,,

ρ=

where A

LA

M,ρ

= molar density of A in the liquid phase ( 3mkmol ).

Again, under pseudo-steady-state conditions, these two equations may be equated:

( )

lmB

AA

A

LA

yyy

dtdz

M ,

21AB,

LcD −

=ρ

The above equation may be integrated from t = 0 to t = t and from z = L0 to z = L and yields

( )

( )2

20

2

21

,, LLyyctMy

DAA

AlmBLAAB

−

−=ρ

Arnold Cell Apparatus The Arnold cell apparatus consists of an acrylic assembly sub-divided into two compartments (see next page). One compartment is used as a constant temperature water bath. The other compartment incorporates an air pump and necessary electrical controls for the equipment.


24

Figure 4.2 Schematic of Arnold cell.

Water in the water bath is heated by an immersion heater which is controlled to a tolerance of ±1°C.

The capillary tube utilized for the determination of the diffusivity coefficients is mounted on top of the constant temperature water bath. The total capillary length is 10.5 cm. Air can be supplied to the capillary tube by a flexible tube connected to the air pump. The height of the liquid in the capillary can measured using a traveling microscope mounted on a removable support stand that incorporates a vernier height gage.

Procedures

1. Partially fill the capillary tube with acetone to a depth of approximately 35 mm. Remove the top nut from the metal Swage-lok fitting. Carefully insert the capillary tube through the rubber ring inside of the metal nut until the top of the tube rests on the top of the nut. Gently screw this assembly into the top plate stopping with the “T” piece normal to the microscope. GENTLY connect the air tube to one end of the “T” piece and adjust the object lens to within 20-30 mm of the tank.

2. Adjust the vertical height of the microscope until the capillary tube becomes visible. To improve initial visibility of the tube, first adjust the object lens (closest to the tank) until the tube becomes clearer. Finer adjustment of the


25

focus on the meniscus is accomplished with the eyepiece lens. (The capillary tube the image will be upside down.) When the meniscus has been determined, align the sliding vernier scale with a suitable graduation on the fixed scale.

3. Turn on the air pump, and record the level inside of the capillary. Turn on the temperature controlled water bath and wait for the temperature to reach the desired temperature . Read the level and from this determine L0.

4. Record L and t, and repeat at regular time intervals.

References: Welty, J.R., Wicks, C.E., and Wilson, R.E. Fundamentals of Momentum, Heat, and Mass Transfer. 3rd ed., John Wiley & Sons, Inc., 1984.

Suggested Topics to Address in the Discussion of results.

1. Both your results and those from handbooks were determined from experimentation. Why wouldn’t your data be just as valid as that found in an engineering handbook? What were the most likely sources of error for the experiment?

2. Propose a method by which the aqueous phase diffusion coefficient of acetone could be measured simply in a laboratory. This need not be sophisticated, but think of principles and problem solving strategies developed in CHE 120 that could be used to determine Dacetone/H2O from easily measurable parameters in a laboratory. Do you expect the aqueous phase diffusion coefficient to be bigger or smaller than the value you measured here? Why?


26

Exercise #3 - Aeration KLa values

Experimental Objectives A commonly used parameter in gas-liquid mass transfer systems is the overall gas transfer coefficient, KLa, which combines several physicochemical parameters. In this module please address two or more of the following objectives:

1) to determine the value of the overall mass transfer coefficient, KLa, in a batch mechanical aerator using a dynamic measurement technique

2) to determine the effect of stirrer speed and paddle size on KLa,

3) determine the effect of salinity on KLa.

Background

Gas-liquid mass transfer is often accomplished in well-mixed tank systems. In particular, aeration of water typically involves the introduction of compressed air into the bottom of a well mixed tank through dispersers such as perforated pipes, porous sparger tubes, or porous plates. These dispersers introduce air as small bubbles that rise through the overlying water, allowing air-water transfer of oxygen to occur across the cumulative interface of the bubbles within the system. The rate of mass transfer will control the rate of aeration (i.e., the rate at which the oxygen concentration in the water increases over time). Thus, variables that influence the rate of mass transfer can be used as variables for process optimization. In this laboratory, you will be examining several potential process variables that may or may not influence aeration rates.

Experimental Apparatus Equipment and supplies provided for this laboratory exercise include:

1. Armfield fluid mixing apparatus and accessories. The reactor vessel holds up to X liters of water, and is connected to a variable speed motor that allows for agitation of the fluid via a paddle mixer. Note that several sizes of paddles are provided for mixing. At the bottom of the vessel are several gas dispersion stones that can be used to deoxygenate the water supply (when nitrogen is fed through the dispersion stones) or aerate the water supply (when air is supplied through the dispersion stones). The feed gas composition can be controlled by regulators connected to the nitrogen and air tanks. A flow valve is also provided so that the rate of gas flow delivered into the system can be controlled.

2. Dissolved oxygen meter and probe

3. Salt (NaCl)


27

4. Pan balance

5. Ruler, stop watch, thermometer and barometer

6. Nitrogen and air cylinders

Procedures The general procedure for each KLa measurement is outlined below.

Fill the reactor with the appropriate solution and determine its volume. Measure and record the temperature of the solution and the atmospheric pressure.

1. Deoxygenate the solution by first introducing nitrogen gas into the bottom of the tank. The flow of nitrogen should be the same as the air rate that will be used for the desired test.

2. Monitor the dissolved oxygen concentration. When the dissolved oxygen concentration is zero or very close to zero, switch the gas flow from nitrogen to air.

3. Record dissolved oxygen concentration as a function of time.

References

Welty, J.R., Wicks, C.E., and Wilson, R.E. Fundamentals of Momentum, Heat, and Mass Transfer. 3rd ed., John Wiley & Sons, Inc., 1984.

Suggested Discussion Questions to Address in the Laboratory Report Aeration is a common process in wastewater treatment, in which air is introduced into secondary effluent (i.e., effluent that has already undergone biological treatment during which oxygen can be consumed) to increase the dissolved oxygen (DO) concentration prior to effluent discharge into the environment. For wastewater treatment, can you think of other potential variables that might influence air-water exchange? Please be sure to provide an explanation for your suggestion of each variable.


28

Exercise #4 - Liquid Diffusion The design and operation of process plants to achieve the desired changes in materials depends upon the properties of the materials (or contaminants) in a flowing medium (gas or liquid). One of the most important properties of materials in fluids under such circumstances is diffusivity. Fluid flow and mass transfer operations depend to some extent on this property and such data are always needed in plant design.

Experimental Objectives Design and conduct the experiment to determine the diffusivity of a dissolved sodium chloride in water and compare the experimental data with published data from a handbook using one-dimensional diffusion cell.

Background

Fick’s first law defines the diffusion of a dissolved component in an isothermal, isobaric system. In one dimension, the Fick rate equation is:

dxdCDJ A

ABxA −=,

where =xAJ , constant molar flux of A (sm

kmolw ⋅

) in the x-direction, ABD = diffusion

coefficient of A through B ( sm2 ), and

dzdCA = concentration gradient of A in the x-

direction.

The total mass transfer rate (in one dimension) due to diffusion can be determined by multiplying the flux rate times the cross-sectional diffusion area.

dxdCADM A

ABxA −=,!

where xAM ,! is the total transfer rate ( s

kmol ).

In dilute solutions, the concentration of an ionic (salt) solution can be monitored by measuring the electroconductivity of the solution. The molarity of a solution can be determined directly.

€

M =kCM


29

where M = molarity (mole/L), k = conductivity (µS cm-1), and CM = proportionality factor (µS cm-1 M-1). CM varies with salt. For NaCl, CM = 9.67 µS cm-1 M-1.

Incorporating this into the previous equation:

dxdCAD

dtdk

CV A

ABM

−=

where V = volume of reactor into which mass is being transferred.

The diffusion coefficient, DAB, can be determined by:

AM

AB dCdx

dtdk

ACVD −=

Reference: Welty, J.R., Wicks, C.E., and Wilson, R.E. Fundamentals of Momentum, Heat, and Mass Transfer. 3rd ed., John Wiley & Sons, Inc., 1984.

Experimental Apparatus

The liquid diffusion apparatus consists of a variable speed magnetic stirrer and stir bar for agitation of the test solution. A specially designed diffusion cell is mounted to the top of the stirred vessel and clamped into position using the locking screw. At the base of the stirred vessel is a connection for the conductivity cell, which is connected to the conductivity meter with data acquisition system.

The apparatus uses vertical capillaries 5 mm long and 1mm bore (inside diameter) to restrict the diffusion to one dimension. Salt concentration will be effectively zero in the water end and 2M at the concentrated salt solution end.

Procedures

1. Completely fill the diffusion cell with 2M NaCl solution. Wipe of any excess. Clamp cell into position. DO NOT SPILL into the outer vessel. Fill the outer vessel with distilled or equivalent water. Record the amount and temperature of water used to fill the vessel.

2. Check the conductivity meter and make sure the initial reading is below 10-4 Ω-

1.

3. Turn on the magnetic stirrer to GENTLY agitate the water. Record the conductivity at regular intervals.

4. Generate a calibration curve to confirm the constant Cm


30

Figure 4.3 Schematic of one-dimensional diffusion cell.

Suggested Discussion Question to Address in the Laboratory Report Discussion the relative magnitudes of diffusion coefficients for gases, liquids, and solids.


31

Exercise #5 - Wetted Wall Absorber Experimental Objectives A wetted wall absorber is commonly used to study gas-liquid mass transfer. This device provides a well-defined area of contact between the two phases. A thin liquid film flows along the wall of the absorption column while in contact with a gas phase. The objectives for this laboratory exercise are

1) to determine the relationship between mass flow rate and the mass transfer coefficient, kL, and to compare the experimental results with other empirical relationships reported in engineering textbooks.

2) to prepare an appropriate plot of Sh versus Re for the experimental data. Determine the slope of the resultant best-fit line and compare results to the Vivian and Peaceman equation

Wetted wall absorption apparatus The wetted wall absorption apparatus consists of an absorption column connected to a feed chamber of water. A pump is used to deliver the water to the top of the absorption column, where it cascades down the sides of the column to develop a falling water film that is ideal for air-water gas exchange. The apparatus allows the water flow rate to be controlled between ~100 and 300 cc/min. An air compressor delivers airflow outside the falling film, with the rate of air flow controlled by regulator between 1000 and 3000 cc/min.

Adjacent to the absorption column is a deoxygenator column, through which water from the supply tank first passes. In the deoxygenator column, nitrogen gas can be used to remove oxygen from the feed water supply, thereby creating a low dissolved oxygen concentration at the top of the absorption column (check with TA to make sure the water is being degassed properly during operation). Dissolved oxygen probes are provided at the top and bottom of the absorption column to allow oxygen concentration to be monitored during absorption column operation. A thermometer is also available so that the temperature of water can be measured during operation.

Procedures

1. Turn on the supply switch and start the deoxygenator vessel feed pump. Admit nitrogen into this vessel and regulate the nitrogen flow until a constant


32

stream of gas bubbles fills the vessel. (NOTE: If a plug flow pattern occurs, the nitrogen flow rate is too high.)

2. Start the compressor and regulate the air flow rate until it reads 1,000 cc/min. Start the wetted wall column feed pump and set the flow rate to 100 cc/min.

3. After the water overflows the top section of the wetted wall column and runs down the inside wall, make sure the whole perimeter is wetted by carefully sliding a brush down the inside of the tube.

4. Allow the system to reach steady state, about five minutes, then take oxygen readings from both the inlet and outlet.

5. Increase the water flow rate. Allow the system to reach steady state again. Take oxygen readings from both the inlet and outlet. Repeat at various water flow rates of.

6. Repeat the experiment for two other air flow rates.


33

1. Absorption column 17. Air compressor 2. Bearing and knife-edge gimbal 18. Sintered metal disk 3. Feed chamber 19. Not available 4. Discharge section 20. Toggle selector switch (not used) 5. Sintered metal disk 21. Deoxygenator vessel feed pump switch 6. Discharge line 22. Wetted wall column feed pump switch 7. Drain valve 23. Air compressor switch 8. Supply tank 24. Main supply switch 9. Sensor probe 25. Not available 10. Adjustable feet 26. Nitrogen tank 11. Dissolved oxygen probe 27. Water flowmeter 12. Sensor probe 28. Air flowmeter 13. Deoxygenator column 29. Electronics cabinet 14. Nitrogen inlet valve 30. Support framework 15. Deoxygenator feed pump 31. Support ring 16. Absorption column feed pump

Reference: Welty, J.R., Wicks, C.E., and Wilson, R.E. Fundamentals of Momentum, Heat, and Mass Transfer. 3rd ed., John Wiley & Sons, Inc., 1984.

Suggested Discussion Question to Address in the Laboratory Report In this experiment, a convective mass transfer coefficient (a kL value) is used to describe mass transfer of oxygen between air and water in the wetted wall absorption column. At a specific point along the columns flow path, derive an expression that relates kL to DO2/water, the diffusion coefficient for molecular oxygen in water.


34

Exercise #6 - Pipe Flow and Fittings Headloss Please design and conduct experiment to achieve the following objectives

1) to determine the relationship between headloss (energy loss) and flow velocity for both laminar and turbulent flow through a pipe and to compare experimental results with the Moody diagram (figure 6.10 in Fluid Mechanics for Chemical Engineering, Third Edition).

2) to determine the relationship between headloss and flow velocity for turbulent flow through various common pipe fittings and to compare experimental results with data found in handbooks.

Experimental Apparatus

Experimental apparatus consisted of fluid friction apparatus with manometer, stop watch, ruler, calipers, and thermometer. Figure 1 shows the diagram of the fluid friction apparatus. The unit consists of a tubular steel framework which supports the network of pipes and fittings for test. Pipe friction experiments can be carried out using four smooth pipes of different diameters, plus one roughened pipe. Short samples of each size test pipe are provided loose so that the students can measure the exact diameter and determine the nature of the internal finish. The test pipe diameters for smooth pipes are 19.1 mm O.D. X 17.2 mm I.D., 12.7 mm O. D. X 10.9 mm I. D., 9.5 mm O. D. X 7.7 mm I. D., 6.4 mm O. D. X 4.5 mm I. D. The diameter of the roughened pipe is 19.1 mm O. D. X 15.2 mm I. D. The test pipe lengths are 1000 mm.

The most common source of errors in this type of system is failure to maintain a “primed” system. “Priming” refers to the process of purging all air from the system and manometers so that only liquid fills the system. Once primed, the system will remain free of air bubbles as long as the pump operates. Also, valves must be opened and closed in the proper order to exclude air from the system. BEFORE THE PUMP IS TURNED ON, ALL valves should be closed. Once the pump is turned on, open the inlet flow control valve (V2) completely. It will remain open throughout the entire experiment. Flow rate is controlled by the outlet flow control valve (V6). DO NOT OPEN V6 YET. To bleed air from the system, open the air bleed valves (V3) in succession. You can see air being purged through the clear tubing. When no more air bubbles are present in the first tube, close that valve and repeat the process for the second valve.

The manometer systems (20 & 21) are fitted with quick connect fittings for easy placement into any desired location. Whenever the pump is shut off or whenever the probes are disconnected, the corresponding manometer valves (V7) must be closed. This procedure ensures that air will not enter the manometers. Pressure drops across two points are measured by placing the probes in appropriate locations, opening the manometer valves (V7), and observing the relevant manometer. Use the water


35

manometer (21) for low pressure differences and the mercury manometer (20) for high pressure differences. It is always safest to start with the mercury manometer.

Flow rate through the system is determined by taking timed readings of the volume collected in the collection tank (22). Volumetric readings can be read from the sight tube (27). Filling and draining of water in the collection tank is controlled by the dump (ball) valve. NOTE: It takes a while for the volume readings to stabilize after the dump valve is closed.

Figure 4.1 Schematic of fluid friction apparatus.

References:

Nevers, N. Fluid Mechanics for Chemical Engineering, 3rd edition, McGraw-Hill’s, 2005

Fox, R.W. and McDonald, A.T., Introduction to Fluid Mechanics, 4th edition, John Wiley & Sons, Inc., 1992.

Brater, E.F. and King, H.W., Handbook of Hydraulics for the Solution of Hydraulic Engineering Problems, 6th ed., McGraw-Hill, Inc., 1976.

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