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THE TEAK PROJECT:
TRAVELING ENGINEERING ACTIVITY KITS
Heat Transfer
Partial support for this project was provided by the National Science Foundation's Course, Curriculum, and Laboratory Improvement (CCLI) program under Award No. 0737462. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Partial support for this project was provided by the American Society for Heating, Refrigeration, and Air-Conditioning Engineering (ASHRAE) through a Senior Projects grant. Any opinions findings and conclusions or recommendations expressed here are those of the author(s) and do not necessarily reflect the views of ASHRAE
ACTIVITY OVERVIEW
Heat Transfer Kit Overview
Your sled dog has abandoned you in the middle of a race, and you’re left with nothing but a few supplies in your backpack to keep you warm! In this kit, students will learn how to use heat transfer principles to save their intrepid adventurer. Engineers, designers, architects, technicians, and many others frequently encounter heat transfer in their daily work. Just as engineers test and collect data about certain materials in order to make good design decisions, the students will do the same to help keep their character warm.
Activity Time Description
Heat vs. Temperature (Conduction) 20 - 25 min Experience the difference between heat and temperature and compare the effects of mass and material on heat transfer. Convection Currents 10 - 15 min Observe the way hot and cold water interact with each other. Keeping-Heat-In Design Challenge (Radiation) 25 - 30 min Design a shelter to keep an IDITAROD Dog Sled Team warm! Optional Extender: Wind Chill 15 - 20 min Experience the wind changing the perceived temperature but not the actual temperature.
Learning Objectives
By the end of this lesson, students should be able to…
- Describe what heat transfer is and what the three basic forms of heat transfer are
- Describe heat versus temperature based on experimental observations
- Work in teams to satisfy a design scenario
- Explain how wind chill affects temperature
NYS Learning Standards
Standard 1 : Students will use mathematical analysis, scientific inquiry, and engineering design, as appropriate, to pose questions, seek answers, and develop solutions. Students will:
- Interpret organized observations and measurements, recognizing simple patterns, sequences, and relationships
- Discuss how best to test the solution; perform the test under teacher supervision; record and portray results through numerical and graphic means; discuss orally why things worked or did not work; and summarize results in writing, suggesting ways to make the solution better Standard 4: Energy exists in many forms, and when these forms change energy is conserved. Students will:
- Describe the sources and identify the transformations of energy observed in everyday life
- Describe situations that support the principle of conservation of energy
INSTRUCTOR PREPARATION GUIDE
Definitions
Heat (Thermal) Energy
Heat energy is a form of energy that is present in the molecules and atoms of an object. When an object is hot, its molecules have a lot of energy and therefore move fast. When an object is cold, the molecules begin to slow down thus decreasing the overall amount of energy. The faster the molecules are moving, the more space they take up.
Heat vs. Temperature
Heat is the energy present in an object. Heat energy depends on many factors, such as how fast particles are moving as well as how many particles are present. Temperature is a measure of the average kinetic energy of the molecules in an object. Temperature is not dependent on number or size. While heat and temperature are different, they are directly related. When an object heats up, its molecules become more excited thus increasing the overall speed at which they travel. A temperature reading of this object will detect the increased kinetic energy of the molecules thus generating a higher temperature reading.
Heat Transfer
Heat transfer is the movement of thermal energy from one object to another. According to the Second Law of Thermodynamics, heat will always transfer from a hotter object to a cooler one. Once heat has begun to transfer from one object to another, it can never be stopped (only slowed down). Heat transfer can also occur when an object is at a different temperature than its surroundings. In this case, the object will gain or lose energy until it is the same temperature as its surroundings. This is known as thermal equilibrium.
Conduction
Conduction is heat transfer through direct contact. When adjacent atoms vibrate or exchange electrons, heat energy is transferred between them. Since conduction requires the physical touching of atoms, it is most common in solids. Substances that easily transfer heat energy are called thermal conductors. Substances that resist heat transfer are called thermal insulators.
Convection
Convection is heat transfer between a solid object and the liquid or gas that is passing by it. The faster the liquid or air is moving, the greater the convective heat transfer will be. There are two types of convection: natural and forced. Natural convection is distinguished by the lack of an external source. The motion of the fluid is caused by temperature variations in the fluid. For example, when air passes over a fire, it heats up and the particles spread out (making it less dense). This causes the air to rise. As the air gets farther from the fire it begins to cool down and the particles contract. This causes it to become denser and sink downward. Forced convection occurs when there is an external source, such as a fan or a pump. The fluid will travel in the path it is directed, as opposed to the rise and fall path of natural convection. An example is a furnace, where air is heated up and forced to follow ducts to certain areas of a house/building.
Radiation
Radiation is heat transfer in the form of electromagnetic waves that carry energy from one object to another. There is no physical medium needed for radiation to occur; it will even work in a vacuum. The most common example of radiation is energy from the sun.
Thermal Conductor
A thermal conductor is a material that allows heat to be transferred through it.
Thermal Insulator
A thermal insulator is a material that reduces the rate of heat transfer by limiting the amount of conduction and/or convection that occurs.
Wind Chill
Wind chill is the apparent temperature felt by a person due to the combination of air temperature and wind speed. While the temperature difference can be perceived, it cannot be measured. Although wind chill is usually associated with winter, it can be felt in warmer weather as well. In the winter, cool breezes make the outside temperature fell colder than it is. When it’s warm out, a fan blowing on a person moves air across their skin and helps it evaporate moisture. The evaporation causes a perceived cooling effect, making the air feel cooler than it actually is.
HEAT TRANSFER INTRODUCTION
Background Information
Heat transfer is the movement of thermal energy from one object to another. According to the Second Law of Thermodynamics, heat will always transfer from a hotter object to a cooler one. Once heat has begun to transfer from one object to another, it can never be stopped (only slowed down). Heat transfer can also occur when an object is at a different temperature than its surroundings. In this case, the object will gain or lose energy until it is the same temperature as its surroundings. This is known as thermal equilibrium.
Simplified Definitions: 5 Minutes
- Heat Energy
- Heat energy is a form of energy that is present in the molecules and atoms of an object.
- The motion of atoms and molecules results in heat energy.
- Conduction
- Conduction is heat transfer through direct contact. When adjacent atoms vibrate or exchange electrons, heat energy is transferred between them. EX: Heating a pot on a stove
- Insulator
- A material that reduces the rate of heat transfer by limiting the amount of conduction and/or convection that occurs.
- Prevents heat moving from one place/object to another.
- Conductor
- A material that allows heat to be transferred through it.
Heat Energy Group Discussion: 5 Minutes
(Pose the following questions to the group and let the discussion flow naturally…try to give positive feedback to each child that contributes to the conversation.)
Q: Do you know what the Universe is made up of?
- Matter and Energy o Matter is made up of atoms and molecules (groupings of atoms). o Energy causes the atoms and molecules to always be in motion - either bumping into each other or vibrating back and forth.
Q: Does matter still have heat energy, even in the coldest environment you can imagine?
- Heat energy is present in all matter.
- Even in the coldest voids of space, matter still has a very small but still measurable amount of heat energy.
Q: What are some ways you can think of to heat up a substance?
- By increasing the speed of its molecules
- By adding energy to it o For example, when we are cold, we can jump up and down to get warmer. o The more energy that goes into a system, the more active its molecules and atoms are.
Q: So then what would happen if we were to take energy away?
- When you take energy away, it cools down.
Q: Do you think the amount of heat a substance has is determined by how fast its molecules are moving?
- Yes - the faster molecules move, the more heat or thermal energy they create.
- How fast the molecules are moving also depends on how much energy is put into them.
Q: Do you think temperature is the same thing as heat?
- No, heat and temperature are different.
- Temperature is a measure of how fast the atoms or molecules of a substance are moving.
- It’s a way to measure how hot or cold and object is.
Q: Heat travels from a hot object to a cold object. So if you pick up an ice cube, which way is heat flowing?
How about if you pick up a cup of hot chocolate?
- From your hand to the ice cube.
- From the hot chocolate to your hand Idea obtained from the ASHREA Cool Science Kit, Module #2 – Part 3.
Learning Objectives
By the end of this exercise, students should be able to…
- Feel/understand that heat and temperature are different
- Observe how mass and temperature affect heat
Materials
Included in each kit are:
- (1) Thermometer
- (1) Spoon
- Paper Towels
- (4) Large Metal Balls
- (4) Small Metal Balls
- (4) Rubber Balls
Safety Precautions
Do NOT use boiling water! Stress that if something is too hot or too cold, to put it down immediately.
Heat vs. Temperature Activity – 15 Minutes
CONVECTION INTRODUCTION
Simplified Definition: 2 Minutes
Convection
- Convection is heat transfer between a solid object and the liquid or gas that is passing by it. The faster the liquid or air is moving, the greater the convective heat transfer will be. EX: Furnace, fire
Convection Group Discussion: 5 Minutes
(Pose the following questions to the group and let the discussion flow naturally…try to give positive feedback to each child that contributes to the conversation.)
Q: Thermal expansion and contraction is when materials grow or shrink when they are heated or cooled.
When something is heated do you think it expands (grows) or contracts (shrinks)?
- It expands when heated.
- It contracts when cooled.
Q: Think about when you are up and running around in gym class, you use a lot of space in the gym and
you get really warm. But when you come back to the classroom and slow down you take up less space and you start to really cool down. The same is true for atoms and molecules, when they are moving fast they take up more space and when they are moving slowly they take up less space.
Q: When atoms and molecules are moving fast and they expand, do you think they rise up or sink lower?
Why?
- They will rise upwards.
- This is because when they separate, they become less dense. For example, if three students are sitting next to one another, they will weight a certain amount. If those same three students get excited and run away from each other, they will weigh the same amount but their weight will be spread out over a greater area.
Q: If hot air rises because it expands, what does cold air do?
- It sinks towards the ground.
Convection Currents Activity – 5 Minutes
Learning Objectives
By the end of this exercise, students should be able to…
- See/understand the way hot and cold fluids move
- Understand the concept of convection
Materials
- Large container with lid
- Small container with lid
- Food coloring
Procedure
- Fill the large container with cold water.
- Fill the small container with hot water and food coloring. ****Try to do the first two steps before starting the lesson****
- Have all the students gather around so that they can see.
- Place the small container into the larger container and remove the lid.
- Explain what is happening to the students. Relate the movement of water to the movement of air. Use the expected results paragraph for a guide of what to mention.
- Replace the lid on the larger container, and empty after the lesson is over.
Expected Results
The warm water will rise out of the small container, since it is less dense than the cold water surrounding it. As the warm water gets cooler it will start to sink towards the bottom of the container. This is because heat is always transferred from hot to cold objects. Eventually, the hot water will become the same temperature as the cold water. This is called thermal equilibrium. The movement of the water demonstrated the concept of natural convection. Some examples of natural convection are: weather, smoke from a fire rising into the air, a loft being warmer than ground level.
End Convection Currents Activity
Learning Objectives
By the end of this exercise, students should be able to…
- Understand the concept of radiation
- See/understand how radiation transfers heat by using thermal crystals
Materials
Each group gets:
- (1) K’nex structure
- (1) Bag of materials
- (2) Thermal crystals Other materials:
- (3) Clip lamps
- (1) Surge Protector
- (3) Laminated Test Layouts
Setup Procedure
(For instructor’s purpose only...DO NOT have students help with this)
- Room Arrangement This activity requires 3 working stations. They all need to be around a central location so that the power cords will reach. Design A: The activity was designed and tested with the clip lamp attached to the back of a chair and the materials set up on a table. This setup allows the students to see what is happening and to easily manipulate the activity. Design B: If the desks and chairs cannot be moved, using only chairs is a suitable alternative.
Keeping-‐Heat-‐In Design Activity – 20 Minutes
- Clip Light Arrangement Make sure that the clip lamps are set up facing away from each other so that they don’t interfere with other groups’ thermal crystals. Design A: Attach clip lamp to the back of the chair
- Structure Arrangement a. Place one test layout at each workstation. Make sure that the layout is in proper position, and then tape it down. The structures/solar panels will go in the labeled boxes on the test layout.
a. While the groups are doing this, the instructor should set up the three clip lamps (making sure that each lamp is set up to allow enough working space for two groups). The instructor should attach each lamp to the surge protector, and plug it in (making sure to switch it off). The instructor should also set up a test layout at each test station. See Setup Procedure for more details.
- Assign each group to a clip lamp. Have the students bring their structure, materials, and thermal crystals to their lamp.
- The instructor should remind the students that the lamps get hot, and they are not to touch them for any reason. Read the instructions to the students step by step. Have a different student perform each step. Have students raise their hands after they complete a step so the instructor knows to move on.
- Record the color of the room temperature thermal crystal. When the lamp is turned on, all students will need to watch the thermal crystals and see the order in which they change colors.
- Place the thermal crystal in the structure box on the test layout. (This is done with no insulation so the students can see how the crystals change color.)
- INSTRUCTOR: Flip the switch on the surge protector to turn on the lamps, then count to 15. When 15 seconds are up, flip the switch back off.
- Record the color of the heated crystal.
- Put the K’NEX structure in the appropriate box on the test layout.
- Put a thermal crystal into the structure. (Make sure that the students hold the crystals on the sides, so as to transfer as little heat as possible to them.)
- Put a material onto the structure. It should be resting on the green pegs and leaning back against the incline. a. INSTRUCTOR: Quickly walk around to make sure that all materials are leaning against the structure so that the thermal crystal will be covered.
- INSTRUCTOR: When everyone is ready, flip the switch to turn the lights on and remind the students not to look into the light. Start the timer when the lights are switched on.
- INSTRUCTOR: When one minute is up, turn the lights off.
- Remove the material from the K’NEX structure and look at the color of the thermal crystal. (This needs to be done quickly, so that the crystal doesn’t start to change colors.)
- Record the color of the thermal crystal.
- INSTRUCTOR: Repeat steps 1 2 - 17 so the students can test their other two materials. b. It may be necessary to repeat the experiment a 4th^ time, in case groups mess up on one of their tests.
End Keeping-‐Heat-‐In Design Activity
Concluding Discussion: 5 Minutes
Q: What material do you think is best to keep the heat in Emmy’s shelter?
Q: Why do you think these materials worked best?
- They are clear and plastic, so they allow radiation in but don’t let heat escape.
- They are not reflective (like the wrapper) so they allow radiation through them.
Q: Did you expect these materials to work best? Why or why not?
- Can be whatever answer the think is correct.
Q: Do you think the idea of trapping radiation/heat is used in engineering today?
- YES! Passive Design
- Engineers and architects use large windows that face the sun to heat up buildings in the winter. The buildings include special overhangs to allow the sun to come in during the winter and to keep it out during the summer.
Q: If you were going to build a structure to try to keep heat out, which materials would work best? Why?
- Insulated foil because the air filled pockets disrupt the heat transfer and the reflective surface keeps radiation from getting through.
- The energy bar wrapper because it reflects the radiation rays away.
Trouble-Shooting Guide
- Crystals turn color without being touched. a. If the classroom is warm, the crystals may show “warmer” colors without being touched.
- The crystals aren’t turning the color ranges described on the handout answer key a. Make sure the structure is in the box on the test layout. b. Make sure that the test layout is positioned correctly. c. Make sure the lamp is angled down so that it is aiming at the structure. d. Make sure the students are checking the thermal crystal color promptly after the light is turned off.
WIND CHILL INTRODUCTION
Background Information
Wind chill is the apparent temperature felt by a person due to the combination of air temperature and wind speed. While the temperature difference can be perceived, it cannot be measured. Although wind chill is usually associated with winter, it can be felt in warmer weather as well. In the winter, cool breezes make the outside temperature fell colder than it is. When it’s warm out, a fan blowing on a person moves air across their skin and helps it evaporate moisture. The evaporation causes a perceived cooling effect, making the air feel cooler than it is.
Simplified Definition: 1 Minute
- Wind Chill o The temperature felt by a person due to the combination of air temperature and wind speed. While the temperature difference can be felt, it cannot be measured.
Group Discussion: 5 Minutes
(Pose the following questions to the group and let the discussion flow naturally… try to give positive feedback to each child that contributes to the conversation)
Q: Has anyone heard of or experienced wind chill? When was it?
- Hopefully people have heard of wind chill. If not, mention winter months and how schools usually close if the wind chill is too bad.
- Usually, people associate wind chill with the winter months.
Q: Does anyone think that wind chill can happen in warm weather?
- The students may answer yes or no.
- Either way, explain that a fan blowing on a person when it’s warm out creates a wind chill effect. The fan blows air across a person’s skin and helps moisture evaporate. The evaporation makes the person feel cooler than they are. This temperature difference is only felt; it cannot be measured.
TEAK Heat Transfer Lesson Plan Page 20
Learning Objectives
By the end of this exercise, students should be able to…
- Understand the concept of wind chill
- Feel a perceived temperature difference
Materials
- (3) Clip Lamps
- IR Thermometer
- (3) Mini-fans
Safety Precautions
The lamps get very hot! Instruct the students NOT to touch the lamps for any reason. They should ask for assistance if they need to adjust their lamp.
Procedure
- The instructor will need to paint/color a small black square onto their hand. A piece of construction paper could also be taped on. This needs to be done so that the IR Thermometer will get an accurate reading (just using your skin will cause jumpy, inaccurate temp. measurements).
- Have all of the students gather around one clip light. The instructor should plug in the clip light.
- The instructor should put his/her hand under the light. Count to 20 and then measure the temperature of the square using the IR thermometer.
- Have a student turn on a mini-fan and aim it at the instructor’s hand. Count to 20 seconds again, and then retake the temperature of the square. The temperature should be the same (or very close). The instructor should tell the students if their hand feels colder.
- Have the students return to their assigned clip light from the previous activity.
- Have students take turns putting their hands under the light with and without the fan to experience the perceived temperature change. Remind the students that the temperature of their skin is not changing, as demonstrated by the IR thermometer.
- After everyone has had a turn, unplug all the clip lights and put them away.
Concluding Discussion: 1 Minute
Q: Did this activity help you to see that wind chill can be felt in a warm area too?
- Whatever answer they give will be correct.
Q: Did it surprise you that your hand felt cooler, but it was actually the same temperature?
- Whatever answer they give will be correct.
Wind Chill Activity – 10 Minutes
End Wind Chill Activity
