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Materials/Processes

Selection of Materials
Specific Metals
  Metal Ores
  Iron and Steel
  Decarburization
  Aluminum/Aluminum Alloys
  Nickel and Nickel Alloys
  Titanium and Titanium Alloys


General Manufacturing Processes

Metallic Components
Ceramic and Glass Components
Polymers/Plastic Components
Composites

Manufacturing Defects
Metals
Polymers
Composites

Service Induced Damage
Metals
Polymers
Composites
Material Specifications

Component Design, Performance and NDE
Strength
Durability
Fracture Mechanics
Nondestructive Evaluation

Thermal Conductivity

Thermal conductivity (λ) is the intrinsic property of a material which relates its ability to conduct heat. Heat transfer by conduction involves transfer of energy within a material without any motion of the material as a whole. Conduction takes place when a temperature gradient exists in a solid (or stationary fluid) medium. Conductive heat flow occurs in the direction of decreasing temperature because higher temperature equates to higher molecular energy or more molecular movement. Energy is transferred from the more energetic to the less energetic molecules when neighboring molecules collide. 

Thermal conductivity is defined as the quantity of heat (Q) transmitted through a unit thickness (L) in a direction normal to a surface of unit area (A) due to a unit temperature gradient (ΔT) under steady state conditions and when the heat transfer is dependent only on the temperature gradient. In equation form this becomes the following:

Thermal Conductivity = heat × distance / (area × temperature gradient)

λ
= Q × L / (A × ΔT)

Approximate values of thermal conductivity for some common materials are presented in the table below.

 Material

Thermal Conductivity
W/m, oK

Thermal Conductivity
(cal/sec)/(cm2, oC/cm)

 Air at 0 C

0.024

0.000057

 Aluminum

205.0

0.50

 Brass

109.0

-

 Concrete

0.8

0.002

 Copper

385.0

0.99

 Glass, ordinary

0.8

0.0025

 Gold

310

-

 Ice

1.6

0.005

 Iron

-

0.163

 Lead

34.7

0.083

 Polyethylene HD

0.5

-

 Polystyrene expanded

0.03

-

 Silver

406.0

1.01

 Styrofoam

0.01

-

 Steel

50.2

-

 Water at 20 C

-

0.0014

 Wood

0.12-0.04

0.0001