**Unit 5: Radiation**
*In this unit, we will study the third mode of heat transfer:
radiation. Unlike conduction (Unit 2) and convection (Unit 3), thermal
radiation does not require matter to act as its medium of transference.
In this unit, we will first look at the basic terminology and
fundamental equations of radiation. You will first be introduced to
blackbody radiation heat transfer and then move onto how to calculate
exchange of radiative energy between two surfaces.*

**Unit 5 Time Advisory**

This unit will take you approximately 20 hours to complete.

☐ Subunit 5.1: 2 hours

☐ Subunit 5.2: 4 hours

☐ Video Lecture: 1 hour

☐ Reading: 3 hours

☐ Subunit 5.3: 4 hours

☐ Video Lecture: 1 hour

☐ Reading: 3 hours

☐ Subunit 5.4: 4 hours

☐ Video Lecture: 1 hour

☐ Reading: 3 hours

☐ Subunit 5.5: 6 hours

☐ Video Lecture: 1 hour

☐ Reading: 5 hours

**Unit5 Learning Outcomes**

Upon successful completion of this unit, the student will be able to:
- Calculate radiation heat transfer between surfaces and their
enclosures.
- Define radiation properties of materials.
- Explain the mechanisms underlying solar radiation.
- Calculate heat transfer with combined conduction, convection and
radiation.
- Explain Kirchhoff’s Law.
- Calculate radiation heat transfer between two gray bodies.

**5.1 Fundamentals of Radiation**
- **Reading: Infrared Imaging Experiments’ “Conduction, Convection and
Radiation from A Light Bulb”**
Link: Infrared Imaging Experiments’ “Conduction, Convection and
Radiation from A Light
Bulb” (YouTube)

Instructions: Please click on the above link, which will take you
to a webpage of heat transfer experiments captured by Infrared
video. Browse to the sections titled “Conduction, Convection and
Radiation from A Light Bulb”. Read the descriptions and watch the
video. Click on the link “Read more” if you are interested in a
more detailed description of the experiment. Feel free to watch
other experiments on the website.

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**Reading: MIT: Professors John Lienhard IV and John Lienhard V’s A Heat Transfer Textbook: “Chapter 10: Radiative Heat Transfer”**Link: MIT: Professors John Lienhard IV and John Lienhard V’s A Heat Transfer Textbook: “Chapter 10: Radiative Heat Transfer” (PDF)Instructions: For this unit, please read sections 10.1-10.4 of “Chapter 10: Radiative Heat Transfer” (pp. 527-565), which will introduce you to basic concepts and governing equations of thermal radiation. The reading will cover the material that you need to know for subunits 5.1-5.6.

You should start by reviewing section 1.3, pages 27-32, to make sure that you know all the key ideas of radiation (e.g. blackbody, electromagnetism, absorbance).

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**Lecture: YouTube: Indian Institute of Technology (IIT) Bombay: Professor S.P.Sukhatme and Professor U.N.Gaitonde’s “Lecture 10: Thermal Radiation,” “Lecture 11: Thermal Radiation-2,” “Lecture 12: Thermal Radiation-3,” “Lecture 13: Thermal Radiation-4,” “Lecture 14: Thermal Radiation-5,” and “Lecture 15: Thermal Radiation-6”**Link: YouTube: Indian Institute of Technology (IIT) Bombay: Professor S.P.Sukhatme and Professor U.N.Gaitonde’s “Lecture 10: Thermal Radiation,” “Lecture 11: Thermal Radiation-2,” “Lecture 12: Thermal Radiation-3,” “Lecture 13: Thermal Radiation-4,” “Lecture 14: Thermal Radiation-5,” and “Lecture 15: Thermal Radiation-6” (YouTube)

Instructions: Please watch these videos (about 55-56 minutes for each lecture), which will introduce you to the basic concepts of radiation heat transfer. This video will cover the material that you need to know for subunits 5.1-5.6.

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**5.1.1 Emittance**
*Note: This topic is covered by the resources below subunit 5.1. Read
pages 529-532 of section 10.1 of the Lienhard-Lienhard textbook.*

**5.1.2 Intensity of Radiation**
*Note: This topic is covered by the resources below subunit 5.1. Read
pages 532-535 of section 10.1 of the Lienhard-Lienhard textbook.*

**5.2 Kirchhoff's Law**
- **Reading: MIT: Professors John Lienhard IV and John Lienhard V’s A
Heat Transfer Textbook: “Chapter 10: Radiative Heat Transfer”**
Link: MIT: Professors John Lienhard IV and John Lienhard V’s A Heat
Transfer Textbook: “Chapter 10: Radiative Heat
Transfer” (PDF)

Instructions: For this unit, please read section 10.2 of “Chapter
10: Radiative Heat Transfer,” which will introduce you to
Kirchhoff’s Law. The law states that at thermodynamic equilibrium,
a body emits as much energy as it absorbs from each direction and at
each wavelength. Make sure that you understand the gray body
approximation on page 538.

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**5.3 Radiation Exchange between Two Finite Black Bodies**
- **Reading: MIT: Professors John Lienhard IV and John Lienhard V’s A
Heat Transfer Textbook: “Chapter 10: Radiative Heat Transfer”**
Link: MIT: Professors John Lienhard IV and John Lienhard V’s *A
Heat Transfer Textbook*: “Chapter 10: Radiative Heat
Transfer” (PDF)

Instructions: For this unit, please read section 10.3 of “Chapter
10: Radiative Heat Transfer” (pp. 527-565). You will learn about
how to calculate radiation heat exchange between two finite black
bodies. Make sure that you can explain view factor reciprotiy (pp
540-541). Work through examples 10.1.

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**5.3.1 Calculation of View Factor**
*Note: This topic is covered by the resources below subunit 5.3. Read
pages 542-550 of section 10.3 of the Lienhard-Lienhard textbook. Make
sure that you understand table 10.2 on page 545, which will allow you to
calculate the view factor for a number of two-dimensional
configurations.*

**5.4 Radiation Exchange between Two Gray Bodies**
- *A
Heat Transfer Textbook*: “Chapter 10: Radiative Heat
Transfer”(PDF)

Instructions: For this unit, please read section 10.4 of “Chapter
10: Radiative Heat Transfer” (pp. 527-565). You will learn about
how to calculate radiation heat exchange between gray bodies. Make
sure that you can define irradiance and radiosity, then explain the
analogy between Ohm’s law for electricity and radiation exchange
between two gray bodies. Work through Example 10.5 on page 553.

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**5.5 Solar Radiation**
- **Assessment: The Saylor Foundation's “Unit 5 Assessment”**
Link: The Saylor Foundation's “Unit 5
Assessment”
(PDF)

Instructions: Please complete the linked quiz. When you are done,
check your work against The Saylor Foundation's “Unit 5 Assessment
Answer
Key”
(PDF)

*A Heat Transfer Textbook*: “Chapter 10: Radiative Heat Transfer” (PDF)

Instructions: For this unit, please read section 10.6 of “Chapter 10: Radiative Heat Transfer.”Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.