# ME204: Heat Transfer

Unit 3: Convection   *In this unit, we will study the second mode of heat transfer: convection.  While conduction is the major mode of heat transfer in solids (as you learned in Unit 2), convection is the major mode of heat transfer in fluids.  Convection occurs because of movements of fluids.  Heat is carried away and dispersed thorough the fluid.  Convective heat transfer occurs in nature (e.g. cooling down effects of wind) and in engineering systems (e.g. heating of homes, cooling of equipment).

We will examine two major types of convective heat transfer: forced convection and natural convection.  In forced convection, movement of fluid is due to external forces such as a pump, while in natural convection, it is due to density differences driven by non-uniformity of temperature. *

This unit will take you approximately 32 hours to complete.

☐    Subunit 3.1: 3 hours

☐    Subunit 3.2: 3 hours

☐    Subunit 3.3: 4 hours

☐    Assignment: 1 hour

☐    Subunit 3.4: 2 hours

☐    Subunit 3.5: 2 hours

☐    Subunit 3.6: 2 hours

☐    Subunit 3.7: 8 hours

☐    Video Lectures: 4 hours

☐    Subunit 3.8: 8 hours

☐    Video Lectures: 4 hours

☐    Subunit 3.9: 8 hours

☐    Video Lectures: 4 hours

Unit3 Learning Outcomes
Upon successful completion of this unit, the student will be able to:

• Define Nusselt and Sherwood numbers.
• Calculate heat transfer in convective boundary layers.
• Calculate heat transfer of flows over plane wall, sphere, and cylinder.
• Calculate heat transfer of pipe flows.
• Calculate heat transfer of free convection.

• Web Media: YouTube: Julius Summer Miller’a “Heat Energy Transfer by Convection – Part 1” and “Heat Energy Transfer by Convection – Part 2” Link: YouTube: Julius Summer Miller: “Heat Energy Transfer by Convection – Part 1” and “Heat Energy Transfer by Convection – Part 2” (YouTube)

Instructions: Please watch these two science demonstration video, in which Dr. Julius Summer Miller performed several simple experiments to illustrate heat convection.  You may want to repeat some of these experiments at home.

• Reading: MIT: Professors John Lienhard IV and John Lienhard V’s A Heat Transfer Textbook: “Chapter 6”

Link: MIT: Professors John Lienhard IV and John Lienhard V’s A Heat Transfer Textbook: “Chapter 6” (PDF)

3.1 Introduction to Boundary Layers   Note: This topic is covered by the reading below the Unit 3 introduction.

3.2 Local/Average Convection Coefficients for Heat and Mass Transfer   Note: This topic is covered by the reading below the Unit 3 introduction.

3.3 Laminar and Turbulent Flow   - Reading: MIT: Professors John Lienhard IV and John Lienhard V’s A Heat Transfer Textbook: “Chapter 6” Link: MIT: Professors John Lienhard IV and John Lienhard V’s A Heat Transfer Textbook: “Chapter 6” (PDF)

`````` Instructions: For this unit, please read sections 6.2-6.8 in
“Chapter 6: Laminar and Turbulent Boundary Layers (pp 278-323).”
Note that the reading will cover the material that you need to know
for subunits 3.3-3.6, and any inclusive sub-subunits.  In Section
6.2, you may want to skim through page 288 and focus on equation
6.24 on page 289.  Make sure that you understand figure 6.11.  Pay
attention to sections 6.4 and 6.6, which provide detailed
discussions on the Prandtl number, boundary layer thicknesses, and
the Reynolds analogy.  Browse through section 6.5, because we are
going to revisit this section in subunit 3.7.

displayed on the webpage above.
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3.3.1 Velocity Boundary Layers   Note: This topic is covered by the reading below subunit 3.3.

3.3.2 Thermal Boundary Layers   Note: This topic is covered by the reading below subunit 3.3.

3.4 Boundary Layer Equations   Note: This topic is covered by the reading below subunit 3.3.

3.5 Discussion over Dimensionless Parameters   Note: This topic is covered by the reading below subunit 3.3.

3.6 Reynold's Analogy   Note: This topic is covered by the reading below subunit 3.3.

3.7 External Flow   - Reading: MIT: Professors John Lienhard IV and John Lienhard V’s A Heat Transfer Textbook: “Chapter 7”

``````Link: MIT: Professors John Lienhard IV and John Lienhard V’s A Heat
Transfer Textbook: “[Chapter
7](http://web.mit.edu/lienhard/www/ahtt.html)” (PDF)

you fill in relevant information about you, you will be able to
form is your city, country, and occupation.  The book is in PDF
format (17.2 MB).  Save a copy of the book for future use in this
course.  This is one of the best books on heat transfer.  For this
Configurations” (pp. 342-388).  Note that the reading will cover the
material that you need to know for subunits 3.7 and 3.8.  This
reading will introduce you to heat transfer for external flows, such
as flows over a cylinder, a sphere, and across tube fields and
forced convection heat transfer.

displayed on the webpage above.
``````
• Lecture: YouTube: Indian Institute of Technology (IIT) Bombay: Professor S.P.Sukhatme and Professor U.N.Gaitonde’s “Lecture 18: Forced Convection,” “Lecture 19: Forced Convection-2,” “Lecture 20: Forced Convection-3,” and “Lecture 21: Forced Convection-4”

Link: YouTube: Indian Institute of Technology (IIT) Bombay: Professor S.P.Sukhatme and Professor U.N.Gaitonde’s “Lecture 18: Forced Convection, “Lecture 19: Forced Convection-2, “Lecture 20: Forced Convection-3, and “Lecture 21: Forced Convection - 4 (YouTube) .

Instructions: Please watch these videos (ranging from approximately 45-50 minutes for each video), which will introduce you to the basic concepts of forced convection.  These videos cover the material that you need to know for subunits 3.7 and 3.8.  In Lecture 18, pay attention to definitions of local heat transfer coefficient and average heat transfer coefficient.  Also, make sure that you remember the definitions of Nusselt number, Reynolds number, and Prandtl number.  In Lecture 19, Professor U.N. Gaitonde works through an example of convective heat transfer with constant heat flux at wall.

3.7.1 Introduction to External Flow   Note: This topic is covered by the resources below subunit 3.7.

3.7.2 Flow over a Flat Plate   - Reading: MIT: Professors John Lienhard IV and John Lienhard V’s A Heat Transfer Textbook: “Chapter 6”

``````MIT: Professors John Lienhard IV and John Lienhard V’s A Heat
Transfer Textbook: “[Chapter
6](http://web.mit.edu/lienhard/www/ahtt.html)” (PDF)

you fill in relevant information about you, you will be able to
form is your city, country, and occupation.   The book is in PDF
format (17.2 MB).  Save a copy of the book for future use in this
course.  This is one of the best books on heat transfer.  For this
Turbulent Boundary Layers” (pp. 278-323) carefully.  The reading
introduces you to equations that can be used to calculated heat
transfer coefficient of forced convection over a flat plate.

displayed on the webpage above.
``````

3.7.3 Flow across a Cylinder   Note: This topic is covered by the resources below subunit 3.7

3.7.4 Flow over a Sphere   Note: This topic is covered by the resources below subunit 3.7

3.7.5 Flow across Tube Fields   Note: This topic is covered by the resources below subunit 3.7

3.8 Forced Convection Heat Transfer   Note: This topic is covered by the resources below subunit 3.7.

3.9 Free Convection   - Web Media: Infrared Imaging Experiments’s “Natural Convection - A Vertical View” and “Natural Convection-A Horizontal View” Link: Infrared Imaging Experiments’s “Natural Convection - A Vertical View” and “Natural Convection-A Horizontal View” (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 “Natural Convection - A Vertical View” and “Natural Convection - A Horizontal View.”  Read the descriptions and watch the videos.  Click on the link “Read more” if you are interested in a more detailed description of the experiments.  The videos will provide you some insights into the dynamics of natural convection.

• Reading: MIT: Professors John Lienhard IV and John Lienhard V’s A Heat Transfer Textbook: “Chapter 8” Link: MIT: Professors John Lienhard IV and John Lienhard V’s A Heat Transfer Textbook: “Chapter 8” (PDF)

Instructions: For this subunit, please read sections 8.1-8.4 (pages 399-416), which will introduce you to natural convection and dimensionless numbers characterizing natural convective heat transfer.  Make sure that you know how to define the Raleigh number for different geometrical configuration of the heating surface (section 8.3).

• Lecture: YouTube: Indian Institute of Technology (IIT) Bombay: Prof. S.P.Sukhatme and Prof. U.N.Gaitonde’s “Lecture 22: Natural Convection-1,” “Lecture 23: Natural Convection-2,” and “Lecture 24: Natural Convection-3”

Link: YouTube: Indian Institute of Technology (IIT) Bombay: Professor S.P.Sukhatme and Professor U.N.Gaitonde’s “Lecture 22: Natural Convection-1,”, “Lecture 23: Natural Convection-2,” and “Lecture 24: Natural Convection-3”  (YouTube)

Instructions: Please watch these videos in their entity (about 50-53 minutes for each video), which will introduce you to the basic equations and dimensionless numbers for free convection.

Unit 3 Assessment   - Assessment: California State University Northridge: Larry Caretto's "April 11 Homework" Link: California State University Northridge: Larry Caretto's "April 11 Homework" (HTML).

`````` Instructions: Open the link above that will take you to the
homepage of ME 375 – Heat Transfer taught by Professor Larry