Understanding Infrared Thermography Reading 3

Transient Heat Exchange
The previous discussions of the three types of heat transfer deal with steady
state heat exchange for reasons of simplicity and comprehension. Heat
transfer is assumed to take place between two points, each of which is at a
fixed temperature. However, in many applications, temperatures are in
transition so that the values shown for energy radiated from a target surface
are the instantaneous values at the moment measurements are made. In
many instances, existing transient thermal conditions are exploited to use
thermography to reveal material or structural characteristics in test articles. In
infrared nondestructive testing of materials, thermal injection or active
thermography techniques are used to generate controlled thermal transient
flow based on the fact that uniform structural continuity results in predictable
thermal continuity. These techniques will be discussed in greater detail in
Chapter 5.
Charlie Chong/ Fion Zhang