The document summarizes key points from a lecture on heat transfer and conduction. It introduces one-dimensional steady-state plane wall conduction and Fourier's law. It discusses how the temperature distribution in a medium is important for determining conduction heat flux, thermal stresses, expansions, and structural deflections. Finally, it notes that thermal conductivity depends on the material, with solids generally more conductive than liquids and gases due to electron and phonon transport.

1. ME 333
Heat Transfer
Lecture 3
Spring 2021

2. 2
Ch.2: Introduction to Conduction
• Simplified Conditions
• One-dimensional
• steady-state
• plane wall
Linear Temperature
Distribution
• Objectives of Ch.2:
• A deeper understanding of Fourier’s law
• Thermal conductivity dependence on the nature of the
medium
• Heat Equation that governs the temperature distribution in
a medium

3. Fourier’s Law
3
One-Dimensional Flow:
• Two Characteristics of 1-D flow  ?

4. 4
Heat Flux Vector

5. 5
The Temperature Distribution
 The temperature distribution represents how temperature
varies with position in the medium.
 If this distribution is known, it helps in determining
• Conduction heat flux at any point in the medium using
Fourier’s law,
• Thermal stresses in solids,
• Thermal Expansions,
• Structural deflections.
• Optimized Thickness of Insulation
• Compatibility of Special Thermal Coatings

6. 6
Thermal Conductivity
ksolid>kliquid>kgas
For an isotropic material;
• In solids, transport of thermal energy may be due to the migration of free
electrons and lattice vibrational waves.
• The lattice vibration quanta are termed phonons.

7. 7
Thermal Conductivity (2)
For Conducting Solids For Non-Conducting Solids
For Solids;
For Fluids;