Understanding Infrared Thermography Reading 3

Heat Capacity
The heat capacity of a malerial or a structure describes its ability to store heat.
It is the product of the specific thermal energy C p and the density ρ of the
material. When thermal energy is stored in a structure and then the structure
is placed in a cooler environment, the sections of the structure that have low
heat capacity will change temperature more rapidly because less thermal
energy is stored in them. Consequently, these sections will reach thermal
equilibrium with their surroundings sooner than those sections with higher
heat capacity, The term thermal capacitance is used to describe heat capacity
in terms of an electrical analog. where loss of heat is analogous to loss of
charge on a capacitor. Structures with low thermal capacitance reach
equilibrium sooner when placed in a cooler environmcnt than those with high
thermal capacitance. This phenomenon is exploited when performing
unstimulated nondestructive testing of structures, specifically when locating
water saturated sections on flat roofs. This is discussed in greater detail in
Chapter 5,
Charlie Chong/ Fion Zhang