Laboratory 6:
Thermal Insulation
General Engineering
Polytechnic University
Overview
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Objective
Heat
Equilibrium
Heat Transfer
Conduction
Convection
Radiation
Thermal Insulation
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Materials for Lab
Problem Statement
Guidelines
Procedure
Written Assignment
Written Topics
Recitation Topics
Closing
Objectives
• Understand the concept of heat as a form of
energy
• Learn how heat moves to different objects
• Use your new knowledge to create a
container that keeps an egg from cooling
Heat
• Energy transferred from one object to
another due to a difference in temperature
Equilibrium
• The temperature at all points in a system are
the same
65o
70
73o
70
70o o
125
70o
25
70o
95
70o
39
70o
90
70o
58
50o
70
70o
80
Heat Transfer
• A result of all systems trying to reach
equilibrium
• Heat always travels from higher to lower
temperature
• There must be 2 or more substances in contact
with each other
Direction
• Three types of heat transfer
of Heat
– Conduction
– Convection
– Radiation
Now at
Hot
Cold
equilibrium
Conduction
• Energy transferred from one solid body to
another without passing through a medium
q = kA DT
DX
Iron
Aluminum
q = heat transfer
DT = difference in
temperature
k = coefficient of
DX = length of bar
A = cross-sectional area
thermal conductivity
Convection
• Heat is transferred by mass transport of atoms
• Typically when heat is transferred from a solid
material to a fluid substance (or vice versa)
q = hA DT
Iron
Water
Steel
q = heat transfer
DT = difference in
temperature
h = coefficient of
convection
A =cross-sectional area
Radiation
• Energy is admitted and absorbed by bodies
in the form of electromagnetic waves
• Can travel through a vacuum
q = esAT4
q = heat transfer
T = temperature
e = constant of emissivity
s = Stefan-Boltzman’s constant
A = cross-sectional area
Thermal Insulation
• Prevents a system from quickly reaching
equilibrium
• Examples:
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Clothing
Walls of houses
Refrigerators
Thermos bottles
Materials for Lab
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Foam chips
Plastic wrap
Tape
Cardboard
Aluminum foil
• Thermocouple and
wire connectors
• Thermal LabVIEW
program
• DAQ board
Problem Statement
• Build an insulating container to accept a
hard boiled egg that was just removed from
the hot water.
• The container should aid in reducing the
loss of heat from the hot egg.
Guidelines
• All materials must remain inside the container
• No external heat sources may be used
• Start LabVIEW program when container cover is
closed and egg is inside
• The container may not be held or covered during
temperature readings
• The egg may not be returned to the water
(i.e. No “restarts”)
Procedure
•Pre-Test
•Test
•Post-Test
• Pre-Test
– Brainstorm & sketch a suitable container to
keep the egg warm
– Include a written description of the
dimensions and construction materials
– Build the container according to the sketch
Procedure
•Pre-Test
•Test
•Post-Test
• Test
– Wait to receive boiled egg from instructor
– Attach one end of thermocouple wire to the
egg (They must remain in constant contact)
– Quickly close the container
– Connect thermocouple to pins 1 & 9 on the
DAQ Board
– Start the LabVIEW program
Procedure
•Pre-Test
•Test
•Post-Test
• Post-Test
– Once the time has finished the LabVIEW
program will generate an Excel table
– Use data on the table to create an Excel
graph of Temperature vs. Time
– Print out the graph and table
– Present the Excel data to your instructor for
his/her initials
Written Assignment
• Full Team Report (one report per team)
• Use the guidelines on page 5 for help
• Include original sketches with instructor’s
initials
• Include Excel table and graph
• Include the topics found on the next slide
• Remember to create a title page
Written Topics
• Address each of the following topics and place them in
the proper sections of report
– Describe the guidelines for this lab
– Give reasons for your design
– Find the slope of the last 5 minutes of the graph. Interpret how
the slope and the graph describes the performance of your
container
– Why are some materials better than others for the purpose of the
container?
– What factors would affect the readings you recorded?
– Describe how you would improve your container if you were to
rebuild it
Recitation Topics
• Discuss the strategy employed by the team
in the development of the design
• Discuss the choice of materials and
quantities used. Were some materials better
than others?
• Would this lab be a good competition?
Why or why not?
Closing
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The egg is VERY hot, do not burn yourself
Clean up your workstation when finished
Throw the egg in the garbage after the lab
You may keep the cup for recitation,
otherwise dispose of it properly