Heat Transfer Laboratory
Laboratory Agreement for working in MEEN 464 Heat Transfer Laboratory
When I am working in the Lab;
I will follow all written and oral instructions given by the lab instructor or coordinator.
I agree to follow all warnings given in the lab manual about any piece of equipment.
I will only use the equipment in the way the lab manual says the equipment should be used.
I will wear proper personal protective equipment (PPE) throughout the lab.
If I have a correction or suggestion or state concerns regarding the lab manual, I will discuss it with the lab coordinator before implementing my idea.
I acknowledge that because of the possibility of harm or injury, I will be respectful of my fellow students, my instructor, coordinator, and myself at all times while I am in the lab.
I understand that any horseplay or rough-housing in the lab will not be tolerated. I understand if I exhibit such behavior I can be removed from lab and receive a zero for my work that day.
I will not remove any equipment and/or components from the laboratory.
I will not attempt to use any equipment in the lab for personal experiments that I have not discussed first with the lab coordinator.
I understand that if I make a habit of not listening to the lab instructor or coordinator, not obeying the instructions I am given in lab, or not following any of the above rules I have agreed to, I can be removed from lab permanently and even be asked to drop the course.
I know the location and use of first aid and fire extinguishing equipment.
I refrain from eating, drinking, smoking, chewing gum or applying cosmetics in the laboratory.
I keep my work area clean and free of clutter during lab class.
I will abide by all required safety rules applicable for this laboratory.
I understand and realize that many accidents are caused by carelessness and being in a hurry. I will come to class prepared to be responsible so that the safety and welfare of myself and others is not jeopardized.
I have read these written safety rules prepared by my lab coordinator and agree to follow these and any other rules.
Date _________________ Student___________________________________
In case of accident or emergency contact:
Name:_____________________________ Phone #______________________
Name:_____________________________ Phone #______________________
Please list any known allergies or health problems: (If additional space is needed, please use the back of this sheet.): ______________________________________
Students must know and follow these safety rules and sing the safety agreement before participating in the labs. Students acknowledge that if the student refuses to sign this safety agreement or the student subsequently repeatedly refuses to follow these safety rules and procedures, the student will be banned from participation in the labs.
AMERICAN DISABILITIES ACT
The American Disabilities Act (ADA), is a federal anti-discrimination statute that provides comprehensive civil rights protection for persons with disabilities. Among other things, this legislation requires that all students with disabilities be guaranteed a leaning environment that provides for reasonable accommodation of their disabilities. If you believe you have a disability requiring an accommodation, please contact the Director of Counseling and each of your course instructors at the beginning of the semester.
For many years Aggies have followed a Code of Honor, which is stated in this very simple verse: “An Aggie does not lie, cheat, or steal or tolerate those who do.” As such, it is the responsibility of students and faulty members to help maintain scholastic integrity at the University by refusing to participate in or tolerate scholastic dishonesty. The Aggie Code of Honor and the Scholastic Dishonesty sections in the TAMUQ University Rules handbook will be the standard upon which scholastic integrity is maintained in this course. Students determined to have committed an act of academic dishonesty will be prosecuted to the full extent allowed by university policy. Collaboration on assignments either in-class or out-of-class is forbidden unless permission to do so is granted by your professor. For more information on university policies, see http://student-rules.tamu.edu/aggicode.htm and http://www.tamu.edu/aggiehonor/.
Students required are to attend the class session for each experiment. Students will be grouped in teams of 3 or 4. Each group will conduct the experiments and then prepare a formal report.
Laboratory reports are due in week after the lab time. More details on the format of the lab report is attached.
Student’s presence in the laboratory is required. Absence in a lab session will result losing the credit for that lab to be lost.
Americans with Disabilities Act (ADA) Policy Statement
The Americans with Disabilities Act (ADA) is a federal anti-discrimination statute that provides comprehensive civil rights protection for persons with disabilities. Among other things, this legislation requires that all students with disabilities be guaranteed a learning environment that provides for reasonable accommodation of their disabilities. If you believe you have a disability requiring an accommodation, please contact Disability Services, in Cain Hall, Room B118, or call 845-1637. For additional information visit: http://disability.tamu.edu.
Aggie Honor Code: “An Aggie does not lie, cheat, or steal, or tolerate those who do.”It is the responsibility of students and instructors to help maintain scholastic integrity at the university by refusing to participate in or tolerate scholastic dishonesty.” (pg. 48 Texas A&M University at Qatar, ed. 131Q). Details are available through the Office of the Aggie Honor System
An excerpt from the Philosophy & Rationale section states:
“Apathy or acquiescence in the presence of academic dishonesty is not a neutral act — failure to confront and deter it will reinforce, perpetuate, and enlarge the scope of such misconduct. Academic dishonesty is the most corrosive force in the academic life of a university.”
Course Learning Outcomes
1. Conduct test runs to acquire experimental data, reduce and analyze the data, and present and discuss the results in a written report
2. Prepare formal technical reports that follow the American Society of Mechanical Engineers
guidelines for technical papers
3 Using instruments to measure and control temperatures and heat transfer rates, such as
temperature measuring devices, constant temperature baths, computer-controlled data acquisition systems, electric heaters, digital temperature indicators, and thermometers
4 To help students better understand the heat transfer phenomena they learned in MEEN 461
5 To help students identify, formulate, and solve engineering problems involving heat transfer; i.e. conduction, natural and forced convection, radiation, and heat exchangers.
1 Introduction and overview:
Uncertainty analysis in experimental data 1
2 Temperature and heat measurement:
Calibration of an RTD, temperature measurements, and Stirling cycle 2
3 1-D steady conduction heat transfer:
Heat flux, Conductivity, Fourier’s Law of conduction, contact resistance. 4
4 Forced Convection and fins:
Forced Convection over Extended Surfaces 6
5 Natural convection:
Balance of energy in Natural convection and Radiation heat transfer 9
6 Radiation Heat Transfer:
Effects of temperature on radiation heat transfer 11
7 Heat exchangers
Introduction to Heat Exchangers 13
Relationship of course to Program Outcomes
Course Learning Outcome Assessment Method Program Outcome
1. Ability to apply knowledge of mathematics, science and engineering related to heat transfer problems Quizzes,
2. Ability to design and construct experiments, and analyze and interpret data Quizzes,
3 Ability to work and function in teams Quizzes,
4 Ability to identify, formulate and solve
engineering problems related to conduction, convection, and radiation Quizzes,
5 Ability to write technical report and communicate effectively Project report
6 ability to use the techniques, skills, and modern engineering tools necessary for engineering practice Quizzes,
Technical Report Format
The technical report format for this laboratory falls into nine sections. Please note that poor report preparation (editing mistakes, grammar and typos) will affect the grade of the corresponding section.
1. Cover page 2%
The cover page should include the class name, date assigned, date turned in, class professor, title of experiment, and members of the group.
2. Introduction and Objectives (1 pg.) 8%
The introduction starts with a table of content and should acquaint the reader to the experiment. It should cover the basic concepts being covered in the lab—what they are, why they are important, and how they are to be established through the report. The introduction should provide insight as to why the experiment was conducted in the first place and what the relevant industrial applications may be. The introduction should be brief.
The objectives section should be concluded by clearly stating the objective of the experiment in the lab in no more than one paragraph. It can typically be reworded from the lab experiment handout.
3. Theory and nomenclature (2-3 pg.) 10%
The theory section covers the scientific bases of the experiment and provides the theory that is going to be used to analyzed data or perform other relevant calculations. The relevant equations should be clearly introduces, explained, and numbered. Derivations, if appropriate, should be included. Coping from any text book materials are prohibited.
An organized list of nomenclature should precede the theory. All symbols or variables should be outlined and briefly described.
4. Experimental Apparatus and Procedure (1-2 pg. + Figures) 15%
A description of the apparatus should be provided, a diagram or schematic of the apparatus is
appropriate. In this section the procedure that your group specifically took throughout the experiment should be described. This section should clearly explain what you did in the lab with proper description of the system and methods used. The experimental procedure from the lab experiment handout should not be copied verbatim. Including schematic of the test section, when applicable, is very important and helps you to explain the test clearly.
5. Results (1-2 pg. + Figures) 30%
In this section you present your raw and processed results. The theoretical calculation for the data points are also listed here and compared with the experimental values if your lab requires comparison of experimental values with theory. Pertinent data plots and figures should go here. Figures and tables need to be numbered and have a caption describing the content of the figures.
Plots need to have their axis labeled with proper physical units. If several sets of data is presented in one plot different symbols need to be used for each data set to clearly identify them. Description of the symbols needs to be included either as legend in the plot or in the caption. Students are strongly advised NOT to connect the data points with lines, or even worse, just show a curve fit! This will disqualify all your results section. A sample calculation showing how the equations used, as outlined in Theory and Nomenclature, must be provided for each calculated data point either tabulated or used in the plots. Adequate uncertainty analysis for the data should be incorporated in the figures, if possible.
6. Discussion (2-3 pg.) 20%
In the discussion you should interpret and explain the results, both experimental and comparison with theory, if required. It is important to explain any sources of error that may have been involved in the experiment, including uncertainty in process or measurement systems—what effect does the uncertainty have on your conclusions and the final results? It is here that you demonstrate your understanding of the fundamental concepts being covered.
7. Conclusion (1 pg.) 10%
The conclusions section provides the answers to the outlined objectives as drawn from your results and discussion. Future recommendations and considerations about the lab can also be made here.
8. References and attachments 5%
A list of references must be provided in MLA or any other standard format. Also, you may attach any other information that clarifies the report.
Appendices may contain your raw data, other sample calculations or graphs you had made, and other materials used for the report but not included in the above sections as seen appropriate by the authors. This section will be graded as part of the grads for the sections that it belongs to.
Experiment 1: Temperature Measurements systems
Temperature is one of the principal parameters of thermodynamics. It is a physical property that underlies the common notions of hot and cold. The ability to correctly measure temperature in a system is a fundamental skill required in many engineering and scientific disciplines. The “correct” assessment of temperature requires as much skill on the part of the engineer as it does of the equipment being used. Sensor type, placement, and data reduction are all parts of the temperature measurement equation. While temperature is an inherently obvious quantity to all of us, its precise measurement can prove extremely challenging. This experiment is designed to help student become familiar with different temperature measurement devices and their accuracy. Moreover, in this experiment students learn how to use LabView system to read the output of temperature, and other, sensors attached to a thermofluidic system.
Temperature measurement can be handled in various different ways. In thermometers variation of specific volume of a liquid with temperature allows one to “read” the change in temperature. In a thermocouple, changes in the voltage potential as per the Seabeck effect occur at the interface of two dissimilar metals. The change depends on the temperature of the metals and measuring it allows one to measure the temperature. In resistive temperature devices (RTD) and other thermo-resistors, the resistance of the device changes as temperature of the device changes allowing one to measure the temperature. Light (electromagnetic) emission from an object can be recorded to determine the temperature at the surface if the emissivity of the surface is known.
All of these temperature sensing methods have their potential benefits and drawbacks. Fluid thermometers can only be read as best as the graduations and experimenter’s ability, confusion may arise from the reading around the meniscus of the fluid; on the other hand they are simple, durable, and inexpensive. Thermocouples need to be cold junction calibrated, and, as they are voltage based sensors their readout changes based on the length of thermocouple wire used. Additionally one has to use the same type of metal wire to extend the leads. RTDs generally have a lower resolution than thermocouples and generally require more extensive wiring. While infrared temperature sensors measure surface temperatures very quickly, they are line-of-sight devices and surface conditions can throw off IR based sensors (in terms of surface finish and emissivity). Additionally one cannot record temperatures lower than the temperature of the sensor itself making them generally unusable for cryogenic type applications.
The temperature range and accuracy of the reading also affects one’s ability to make an acceptable reading. The following chart is reproduced from Capgo Measurement, a company that manufactures various temperature sensors.
No measurement device in perfect in responding to change in the magnitude of the property it is measuring. In other words, there is always a time delay between the initial status of the system to the time the measurement system reaches the final value of what it is measuring in the new environment it is placed. For thermal systems, Newton’s Law of Cooling states that the rate of change of the temperature of a body is proportional to the difference of the temperature of the body and the environment it is in
. ?T(t)=?T_0 e^(-t/t) (1)
Where t is the thermal time constant (At t=t => ?T = 0.37). As t goes to infinity increases, ?T approaches 0. From this we can describe the thermal time constant as the time it takes the system to reach 63.2% (or 100%-36.8%) of the initial value.
Application of temperature measurement in a Stirling Cycle:
A Stirling engine is a heat engine that operates by cyclic compression and expansion of air or other gases, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work1. The engine is like a steam engine in that all of the engine’s heat flows in and out through the engine wall (external Engine). Unlike the steam engine’s use of water in both its liquid and gaseous phases as the working fluid, the Stirling engine encloses a fixed quantity of permanently gaseous fluid such as air or helium. As in all heat engines, the general cycle consists of compressing cool gas, heating the gas, expanding the hot gas, and finally cooling the gas before repeating the cycle.
The idealized Stirling cycle consists of four thermodynamic processes acting on the working fluid as shown in the p-v diagram below:
Isothermal Expansion. The expansion-space and associated heat exchanger are maintained at a constant high temperature, and the gas undergoes near-isothermal expansion absorbing heat from the hot source.
Constant-Volume (known as isovolumetric or isochoric) heat-removal. The gas is passed through the regenerator, where it cools transferring heat to the regenerator for use in the next cycle.
Isothermal Compression. The compression space and associated heat exchanger are maintained at a constant low temperature so the gas undergoes near-isothermal compression rejecting heat to the cold sink.
Constant-Volume (known as isovolumetric or isochoric) heat-addition. The gas passes back through the regenerator where it recovers much of the heat transferred during const-volume heat removal, heating up on its way to the expansion space.
Theoretical thermal efficiency equals that of the hypothetical Carnot cycle – i.e. the highest efficiency attainable by any heat engine. However, though it is useful for illustrating general principles, the text book cycle it is a long way from representing what is actually going on inside a practical Stirling engine and should not be regarded as a basis for analysis.
Two different experiments to be carried out within this laboratory:
Using various temperature sensors to verify their relative accuracies of and their response time constants. This includes validating the RTD response curve.
Measuring operating temperatures, and pressure, within a Stirling cycle to determine cycle efficiency, ?_cycle. Creating a PV diagram and measuring RPM indirectly.
The specific reportable objectives of this experiment are to:
Temperature measurement experiments
Plot the temperatures measured from the various temperature sensors at room temperature, in a cold bath, and hot bath.
Determine the thermal time constant for the various sensors.
Calibrate the RTD and plot results accordingly.
Discuss the relative accuracy of the various measurement systems.
Stirling cycle application
Determine the steady-state operating temperatures of the Stirling cycle to calculate idealized thermodynamic cycle efficiency. Perform uncertainty calculations for temperature measurements.
Measure output voltage drop across a resistor for the cycle. Calculate the power. Determine the overall system efficiency (including mechanical and thermodynamic losses).
Plot the pressure variation in the Stirling engine for loaded and unloaded conditions.
Create a P-V diagram of the Stirling cycle off measured data, (make appropriate assumptions).
Determine the speed (RPM) at which the cycle runs during steady state operation in loaded and unloaded conditions. (use the pressure plot)
The experimental materials for the calibration of the RTD and temperature measurements are as follows:
(1) Omega Type ‘T’ Thermocouple
(1) Omega RTD, 0-100 C.
(1) Labview PXI with SCB-68 and CDAQ
(1) 200 O resistor
(1) Temperature controlled hot-bath
(1) Ice bath
The experimental materials for the Stirling cycle are as follows:
(1) A3BS Stirling Cycle with Alcohol Burner
Maximum volume: 44 cm3
Minimum volume: 32 cm3
Volume displacement: 12cm3
Approx max power: 1W
(3) Omega type ‘T’ thermocouples
(1) Agilent U1251A Digital multi-meter
(1) Setra pressure transducer
(1) 200 O nominal resistor
(1) Labview PXI with SCB-68
Experimental Apparatus and Procedure
The experimental apparatus for the temperature uncertainty experiment consist of hot and cold baths, various temperature sensors, a Labview system, and Agilent multi-meter. Sensors will measure the ambient air temperature, then hot bath temperature, then cold bath temperature. The response time from measuring the hot bath to cold bath temperature time will be tracked. The hot baths is an electrical water heater while the cold bath is an ice bath in a large bucket.
The overall experimental station is centralized and shown below. Both experimental setups are to the right of the experimental station.
The Labview Station is setup in a manner that will allow you to conduct both the temperature measurement experiment and Stirling engine experiment with a minimal need to rewire the hardware. The thermocouple data acquisition card is shown below.
The sensors for this experiment are shown below:
The experimental apparatus for the Stirling engine consists of a small Stirling engine, thermocouples, Labview DAQ system, multi-meter, Setra 25 PSIA pressure transducer, and 200 O nominal load resistor.
The Stirling engine is shown above. The alcohol burner provides the heat for the hot side of the cycle. Expanding gasses push the piston forwards and are channeled through the regenerator where they cool down. The cycle beings to compress the cold side piston where the gas is channeled back through the regenerator where they are preheated and enter the hot side piston. The cycle then repeats itself.
The three way switch allows the user to select the output mode of the engine. In the neutral position there is no load on the cycle. In the up position the motor is engaged with the light bulb, adding a load. When the switch is pushed down the output terminals are engaged and, in this case, the cycle is loaded against a 200 O resistor. As hot water and open flame will be used during this experiment proper safety equipment and operating protocols must be used at all times.
Startup Procedure for Temperature Uncertainty Experiment
Read and review all warnings and directions before proceeding.
Turn on the heater (hot bath).
The RTD is connected to the SCB with a 200 O resistor. (See appendix II)
Set the RTD power supply to approximately 12.5 volts.
Calibrate the RTD.
The calibration is done by measuring the temperature in the hot and cold bath with the RTD and the thermometer. Once the thermometer reads 100°C and 0°C respectively measure the output voltage from the RTD. Use these two values to get the calibration equation.
Open and run the corresponding Labview VI.
Operating Procedure for Temperature Uncertainty Experiment
Record the ambient room temperature with, RTD, Thermocouple, and IR thermometer.
Once the hot water bath reaches a continuous boil, measure the temperature of the hot bath starting with the thermocouple. Record the temperature in the chart in the appendix.
WARNING: Be very careful around the boiling water bath! Safety glasses are required.
NOTE: When measuring the temperatures of the baths with the RTD, thermometers, and thermocouple, place the sensor near the top of the bath and try to keep it stationary. Do not move or shake the sensor when it is in the bath. When using the IR thermometer, quickly measure the temperature of the bath from approximately 20-50cm above the bath pointing straight down.
Quickly switch the thermocouple from the hot bath to the cold bath for temperature to reach steady state. Then switch back again from the cold bath to the hot bath until temperature reaches steady state. Do this procedure for 3 runs.
Repeat steps 2 and 3 for the rest of the temperature sensors.
When calibrating the RTD, use the Agilent handheld multi-meter to determine when the RTD temperature has reached steady state conditions. Average this reading for 5-10 seconds using the average function.
For all temperature sensors estimate the uncertainty ranges in your readings.
Shutdown Procedure for Temperature Uncertainty Experiment
Turn off the water heater. Unplug it from the power strip. Replace the lid to the boiling water bath.
Turn off RTD power supply.
Startup Procedure for Temperature Measurements on a Stirling Cycle
Inspect the Stirling engine.
Ensure that three thermocouples have been inserted into the temperature measurement areas or connected to the cold side of the regenerator.
Check to see that methanol has been added to the alcohol burner.
Ensure that the motor mode selector is in the neutral position (middle position).
Attach the BNC cables from the motor outputs so they run across the 200 O resistor.
Record the pressure range values on the pressure transducer.
Open the VI that reads three thermocouples from the engine.
WARNING: Methanol is a dangerous compound. Avoid skin and eye contact. Safety glasses are required.
Operating Procedure for Temperature Measurements on a Stirling Cycle
WARNING: Do not touch any parts of the Stirling engine during or after operation. The Flywheel is capable of spinning at high (1000 RPM+) rotation and the glass coverings may reach temperatures as high as 600 C.
Uncap the alcohol stove. Raise the wick to a height of approximately 5mm.
Use the provided lighter to ignite the wick.
Start the Labview VI.
As the engine heats up spin the flywheel clockwise. The flywheel may spin for only a short time and stop. This is normal.
Continue to try to rotate the flywheel until it spins freely on its own.
Watch the temperature chart on the VI until the temperatures reach steady state. Average the steady state readings.
Set the motor mode selector to output (down).
Using the Agilent multi-meter, measure the average voltage drop across the resistor for a minimum of ten seconds. Record this average in the appendix.
Record the average temperatures in the chart in the appendix.
Operating Procedure for Pressure Measurements on a Stirling Cycle
Open the LabView VI that will read analog voltage input from the pressure transducer.
Turn on the power supply for the transducer to the recommended voltage range.
With the Stirling engine warmed up on either a loaded or unloaded condition run the VI and collect data for approximately 5 seconds. Stop VI and save data.
Change the load condition (to/from unloaded/loaded) and run the VI again for another 5 seconds.
Shutdown Procedure for Temperature Measurements on a Stirling Cycle
Retract the alcohol stove wick and wait until the flame dies down.
Carefully replace the alcohol stove cover. Be careful to avoid touching the Pyrex piston cylinder!
WARNING: Do not touch the Stirling engine at this time!
Data Charts for Experiment 1
Time (s) Cold-Hot Time (s) Hot-Cold
Sensor Run 1 Run 2 Run 3 Average Run 1 Run 2 Run 3 Average Uncertainty
Omega Type ‘T’ TC
Chart 1: Temperature and uncertainties for various sensors
Avg. Forward Hot-side TC (°C)
Avg. Rear Hot-side TC (°C)
Avg. Cold-side TC (°C)
Avg. Voltage Drop (V)
Chart 2: Temperature and voltage drop averages for the Stirling engine running at steady-state conditions.
Heat Transfer Laboratory