Department of Mechanical Engineering

MEP341 Thermal Engineering Laboratory (0-0-3)

II Semester 2011-2012

Jan 2, 2012

Importance of Experimentation

Most students today wonder why we should do any experimentation in the present world of computations. Computers should have replaced experiments fully by now!

It needs only a bit of serious thought to realize that this view could be only of a frog in a well. The experiments are still important due to a variety of reasons:

• A computer is capable of giving us ‘some’ output for ‘some’ input. However, to verify whether that output truly represents the physical phenomenon under consideration, careful experimentation is indispensable.
• Very often, even computational modelling requires input parameters which need to be determined experimentally.
• Engineers use experimentation extensively both in industry and research. In industry, performance characteristics of various devices are largely determined experimentally.
• Moreover, only experimental observations can help discovery of new phenomena.

This course in ‘Thermal Engineering Laboratory’ is essentially a step in training for carrying out experiments in industry or research. One way to get a feel for experimental work in an educational environment is to carry out experiments on standard set-ups. The experimenter, then, only has to measure the outputs for certain values of inputs and carry out the analysis of the data obtained to verify the theory. However, if the student is able to take a few steps back and conceptualise the set-up to achieve certain objectives and subsequently, put the set-up together within the flexibility available in an educational environment, the learning value of the laboratory exercise gets enhanced manifolds. In view of this, the course design has been modified this semester. The main features of the modified laboratory course are as follows:

The students will be required to do three sets of experiments in the entire semester. Four experimental turns will be devoted to each set of experiments. The broad objectives in each set will be spelt out. The First turn will be spent in conceptualizing the experimental set-up and doing the background study. The second and the third turns will be used in putting the set-up together, actual experiments and the analysis of the data. In the fourth turn, each sub-group will be required to make a presentation of their experimental experience and the results obtained.

Needless to say an experiment must be setup with greatest care to give meaningful results, so that the experimenter is able to correlate theory with physical phenomenon. However, if in a certain situation, the experiment does not give expected results, it offers a very valuable opportunity for learning the art of trouble-shooting, through in-depth analysis of the functioning of the entire experimental set-up with a need to understand the behaviour of every component of the set-up.

The class will be divided into sub-groups of 3 or 4. At a time, one or two subgroups shall carry out one set of experiments. The broad category of

It is expected that the students would carry out the experiments in this lab in the above spirit and make the best of this opportunity to supplement the text book knowledge.

Time Table

The scheduled time table for the five groups is:

Tue – G1; Wed – G2; Thu – G3; Fri – Gr4; Mon – Gr 5

Time: 2.00 p.m. to 5.00 p.m. Venue: Thermal Science Lab II 156.

There will be 9 regular experiments in all which will run in a single cycle. Each group will be sub-divided into subgroups of 2 students each. Subgroup doing experiment no.9 in a certain turn, will do experiment no. 1 in the next turn. This time we are also introducing an exercise in design of an experiment and setting up the rig from the material available in the lab. This will constitute the 10^th experiment which will be done by all the groups in the 11^th, 12^th and 13^th weeks of the lab. The evaluation of this turn will be carried out in the 14^th week of the lab. First class will be meant for preparation for the forthcoming experiments, which includes understanding the experimental rigs and familiarization with the instruments used in the laboratory.11^th turn will also serve as the make-up turn for those who had valid reasons for missing the lab.

The class schedule will be as follows:

Week	Activity	Monday Group	Tuesday Group	Wednesday Group	Thursday Group	Friday Group
1	Preparation for experiments	Jan 10	Jan 4	Jan 5	Jan 6	Jan 7
2	Conducting Experiments	Jan 17	Jan 11	Jan 12	Jan 20	Jan 13 (Thu)
3	-do-	Jan 22 (Sat)	Jan 18	Jan 19	Jan 27	Jan 21
4	-do-	Jan 24	Jan 25	Feb 2	Feb 3	Jan 28
5	-do-	Jan 31	Feb 1	Feb 9	Feb 10	Feb 4
6	-do-	Feb 14	Feb 15	Feb 23	Feb 17	Feb 11
7	-do-	Feb 21	Feb 22	Mar 9	Feb 24	Feb 18
8	-do-	Mar 7	Mar 8	Mar 16	Mar 10	Feb 25
9	-do-	Mar 14	Mar 15	Mar 23	Mar 17	Mar 11
10	-do-	Mar 21	Mar 22	Mar 30	Mar 31	Mar 18
11	Introduction to Design of Experimental rigs & make-up turn	Mar 28	Mar 29	Apr 6	Apr 7	Apr 1
12	Design of experimental rigs	Apr 4	Apr 5	Apr 13	Apr 14	Apr 8
13	-do-	Apr 18	Apr 19	Apr 20	Apr 21	Apr 15
14	Evaluation of the design exercise	Apr 25	Apr 26	Apr 27	Apr 28	Apr 29

List of Experiments

1. Measurement of properties of steam using a Marcet Boiler.

2. (a) Determination of calorific value of a solid/liquid fuel.

(b) Calibration of thermocouples

3. Measurement of temperature profile in a pin fin.

4. Determination of effectiveness of a heat exchanger.

5. Determination of performance characteristics of an air turbine.

6. Study of four stroke SI and CI engines and their components.

7. Determination of heat transfer coefficient in free convection

8. Determination of coefficient of performance of a Vapour Compression Refrigeration system

9. Determination of emissivity of a surface

10. Design of an experiment and setting up the rig.

Guidelines for Laboratory Work

During the preparatory turn, the students are required to spend sufficient time on each rig so as to gain clear understanding of the experimental set-up. Following are the guidelines for the preparatory turn.

Guidelines for Preparation for the Experiments.

The experiments in this course are of two kinds – those involving measurements and those involving only careful study of certain equipment without any measurements.

The guidelines given here are for the first category of experiments.

• Any experiment is first characterized by its OBJECTIVES. Please identify the objectives very clearly.
• To start with, do not look at the experimental rig. Instead try to visualize what kind of experimental set-up would be needed to achieve the given objectives and what measurements would be essential for attaining the objective.
• Only after the above step, should you look at the actual set-up. You must, then, try to understand the actual set-up on your own, identifying all the measurements to be made and try to establish the procedure of the experiment on your own. In the process, you must identify what all information must be provided to you for you to be able to do the experiment. Subsequently, you should verify what you have understood on your own with the instructor. If you carry out all this exercise independently before you start taking measurements, the entire process of experimentation will be much more meaningful to you.
• List the measuring instruments used for various measurements. Think whether these instruments can be replaced by others for measuring the same quantity.
• In any experiment, certain conditions will be more critical than the others. Identify the most critical ones, and not so critical ones for the set-up under study.
• Which quantities do you think need to be measured most accurately in the set-up under study? How should this question be answered?
• Can the same set-up be used for attaining some other objectives pertaining to the phenomena under consideration? What modifications will be required for the purpose?
• Which are the fundamental laws relevant to the phenomena under study? How are they being used for attaining the objectives of the experiment?
• If you were to evaluate someone else doing the experiment, what questions other than those listed above, would you like to ask them?
• Make a list of questions for which answers may not be available readily but have to be searched for.

Guidelines for Doing the Experiment

• You must carry A4 size sheets with objectives and the methodology of the experiment to be carried out already written, graph papers, lab handouts and relevant books for every class.
• You should start recording the measurements only after you have understood the basic principles behind doing the experiment and importance of each measurement. This must be done prior to the lab class hours.
• You must draw a schematic of the set-up used and understand the importance of each component in the set-up.
• All the measurements must be neatly recorded on the final record sheets directly and must be signed by the instructor/TA after the experiment is over. This should be a part of the report of the experiment.
• Every measurement has an uncertainty associated with it. You must carry out an uncertainty analysis in every experiment in which you are making measurements and determine the expected error limits on your experimental results. Hence identify the quantity which should be measured with high accuracy to reduce the overall error substantially.

Guidelines for Report

• Every report must have a cover page with the following information
• Title of the experiment.
• Names and Entry numbers of students who have done that experiment. .
• Group and sub-group.
• Date on which the experiment was done.
• Date on which it was submitted to the instructor/TA for evaluation.

· A template for the above is being provided. Please make copies of this template to be used for each report.

· Please do not reproduce theory from books in your report. The report must give the objectives clearly, a schematic of the experimental set-up with its brief description. The raw data recorded in the laboratory must be a part of the report along with a sample calculation for getting the desired result.

· Only one sample calculation should be done by hand. Repetitive calculations can be performed using a software.

· However, due to lack of printing facility in the lab, the important results will have to be handwritten in the report. The same is also important for you to get the feel for numbers.

· The graphs must be plotted on a graph sheet manually.

· The uncertainty analysis must be included in the report wherever applicable

· The report must include discussion where you give your comments on the results obtained, with possible problems, sources of error, suggestions for improvement etc.

· It is recommended that the group report be prepared jointly so that every member of the group gets to learn each experiment well.

· The report must be prepared in the class itself and submitted at the end of the class. No late submission will be accepted.

Attendance

• Attendance is compulsory in all 14 classes as mentioned above. Missing any one of these turns will be considered equivalent to missing one experiment. Please report in time.
• In general, a student missing a turn will not be allowed to make-up for the missed turn.
• Only if a student is unwell and sends information about the same by the beginning of the lab class, he/she may be allowed to make-up for the missed experiment on verification of the genuineness of the cause.
• If a student is missing the class for Robocon or any other academic event, prior and written permission of the instructor must be sought if the missed experiment has to be made-up for.
• In any case, no student will be allowed to make-up for more than one experiment during the entire semester.
• Missed experiment must be done only during the make-up turn in the last week of the semester.
• Students must report in time. Students arriving late will not be allowed to work in the lab.

Evaluation

Ø Evaluation in the lab for each experiment will have two components : (a) the preparedness for the experiment and the seriousness with which the experiment is conducted. (b) the report and the clarifications on the report, if any.

Ø There will be a self-study component in the course : the students will be expected to read about the various measuring instruments used in thermal engineering. An outline of the same with references is being provided.

Ø There will be two common quizzes. The first one will be to test the self-study part covering the basic concepts of the different measuring instruments. The second quiz will be to test the students’ understanding of the experiments performed by them.

Weightages

Laboratory work and reports 60%

Common Quiz I 15%

Common Quiz II 25%

Tentative dates for Quizzes

Common Quiz I : Feb 15 (Tue), 2010, 5.00-6.00 p.m. (Venue to be announced later)

Common Quiz II: April 19 (Tue), 2010, 5.00-6.30 p.m. (Venue to be announced later)

Instructors :

Dr Prabal Talukdar (Office : III 368) : For Monday, Wednesday and Thursday

Dr Sangeeta Kohli (Office : III 367) : For Tuesday and Friday (Course Co-ordinator).

Topics for Self-study

Errors in Experimentation – Systematic and Random errors; Precision and Accuracy of Measuring Instruments; Uncertainty Analysis

Basic Principles of the Following Measurements

Temperature : Thermocouples, Resistance Temperature Detectors (RTDs), Thermistors

Pressure : Manometers, Bourdon Gauge, Pressure Transducers.

Fluid Flow : Pitot Probe, Pitot-Static Probe, Turbine Flowmeters, Venturimeter, Orificemeter, Vane type Anemometer, Hot wire Anemometer, Rotameter.

Torque : Different types of Dynamometers – belt, eddy current, hydraulic.

Force : Load Cells.

References

1. E.O. Doeblin, Measurement Systems – Application and Design, McGraw Hill.
2. J.W. Dally, W.F. Riley and K.G. McConnell, Instrumentation for Engineering Measurements, John Wiley & Sons.
3. B.C. Nakra and K.K. Chaudhry, Instrumentation, Measurement and Analysis, Tata McGraw Hill.
4. www.omega.com
5. Any other book on instrumentation and measurements from the library (several books are available).

MEP341 Thermal Engineering Laboratory

Lab Report

Group :

Subgroup :

Experiment No.

Title :

Date of Conducting the Experiment :

	Entry No.	Name
1
2

Date of Report Submission :

TA’s Initials (after report correction)

Instructor’s Signatures with Date

Grade/Marks (to be given by the instructor):