Introduction - Heat Transfer

1. 103306-Heat Transfer
King Mongkut’s University of Technology North Bangkok
Faculty of Engineering
Department of Mechanical Engineering

2. Relevance of Heat Transfer
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 Electric Power Generation
 Alternate Energy Systems
 Combustion/Propulsion Systems
 Building Design
 Heating & Cooling Systems
 Domestic Appliances
 Materials/Food Processing
 Electronics Cooling & Packaging
 Cryogenics
 Environmental Processes
 Space Vehicle Systems

3. Course Description
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 Basic Heat Transfer,
 Introduction to conduction, convection, and radiation
heat transfer;
 heat exchangers

4. Outcomes
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By the end, the students should be able to:
 have a good understanding of heat transfer
fundamentals.
 have a theoretical and practical background in heat
transfer.
 have the ability to analyse thermal systems.
 be able to use their knowledge of heat transfer to solve
a problem.

5. Objective of this course
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 Students will learn the fundamental principles of
heat transfer.
 Students will learn to solve ordinary and partial
differential equations.
 Students will be able to analyse a heat exchanger.
 Students will be able to work on multimode heat
transfer applications.

6. Prerequisites
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 Thermodynamics
 Fluid Mechanics
Students who do not have the proper prerequisites
CANNOT take this course.

7. Assessment
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 Quizzes, Homeworks 10%
 Midterm Exam 40%
 Final Exam 50%
!!! NO extra work will be given to individual students
to improve grades. !!!

8. Course materials
Heat Transfer 103306Course Introduction
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 Heat Transfer and Mass Transfer, A Practical
Approach, Yunus A. Cengel, 3rd Edition (SI Unit)

9. Heat Transfer 103306Course Introduction
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 Ch 1: Introduction and Basic Concepts
 Ch 2: Heat Conduction Equation
 Ch 3: Steady Heat Conduction
 Ch 4: Transient Heat Conduction
 Ch 6: Fundamental of Convection
 Ch 7: External Forced Convection
 Ch 8: Internal Forced Convection
 Ch 11: Heat Exchangers
 Ch 12: Fundamental of Thermal Radiation
 Ch 13: Radiation Heat Transfer
Topic

10. Heat Transfer
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 When two objects of different temperatures are
placed in thermal contact, the temperature of the
warmer decreases and the temperature of the cooler
increases
 However, this doesn't happen instantaneously, it takes
time for the transfer of energy to take place.
 Different materials transfer the heat at different
rates.

11. 3 Methods of Heat Transfer
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 Conduction: heat transfer which occurs by atoms and molecules
bumping into each other and passing momentum and energy
through collisions.
 Convection: heat transfer which occurs due to molecules moving
about and mixing while carrying the energy along with them.
 Radiation: heat transfer which occurs due to the emission and
absorption of electromagnetic radiation between bodies.

12.  The molecules vibrate about
their equilibrium positions
 Particles near the stove coil
vibrate with larger amplitudes
 These collide with adjacent
molecules and transfer some
energy
 Eventually, the energy travels
entirely through the pan and its
handle
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Conduction

13. Conduction, cont.
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 In general, metals are good conductors
 They contain large numbers of electrons that are relatively
free to move through the metal
 They can transport energy from one region to another
 Conduction can occur only if there is a difference in
temperature between two parts of the conducting
medium

14. Convection
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 Energy transferred by the movement of a substance
 When the movement results from differences in density,
it is called natural convection
 When the movement is forced by a fan or a pump, it is
called forced convection

15.  Air directly above the
flame is warmed and
expands
 The density of the air
decreases, and it rises
 The mass of air warms
the hand as it moves
by
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Convection, cont.

16. Radiation
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 Radiation does not require physical contact
 All objects radiate energy continuously in the form of
electromagnetic waves due to thermal vibrations of the
molecules
 Rate of radiation is given by Stefan’s Law

17. Objectives of a Heat Transfer
Calculation
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 ANALYSIS
 Calculate T(x,y,z,t) or q for a system undergoing a specified
process
 e.g., calculate daily heat loss from a house
 e.g., calculate operating temperature of a semiconductor chip with
heat sink/fan
 DESIGN
 Determine a configuration and operating conditions that yield a
specified T(x,y,z,t) or q
 e.g., determine insulation needed to meet a specified daily heat loss
from a house
 e.g., determine heat sink and/or fan needed to keep operating
temperature of a semiconductor chip below a specified value