Thermography Flashcards
Thermography - What is it?
A normal camera takes photographs looking for light.
A thermal camera takes thermograms looking for heat.
Key attributes
Real time
Non-destructive testing (non-contact)
Multi-point analysis
Dynamic
Speed of response
Thermal signature
On-board analysis software
Where it is used?
Electrical
Mechanical
Process applications
Medical
Equine
Surveillance
Astronomy
Automobiles
Environmental
Meteorology
Civil (construction and buildings – including civil engineering projects)
Thermography - Definition
“The use of radiant heat emitted by a body to construct images of temperatures.”
Thermography - Heat vs Temperature
Heat is energy in transit.
Temperature is a measurement of this energy.
There are three forms of heat transfer: conduction, convection, and radiation.
There is also evaporation and condensation (phase changes).
Thermography - Heat Transfer - Conduction
Occurs within a substance when heat is applied.
Increased energy = molecular movement/vibration
Heat transferred from one vibrating molecule to the next.
Expansion and contraction.
Thermography - Heat Transfer - Convection
Occurs when you apply heat to a fluid (liquids & gases).
Less bonding between the molecules in convection = heat transfer through molecular displacement.
Gravity has a role to play in convection:
Hot/less dense molecules rise.
Cooler/more dense molecules fall.
Convection currents.
Thermography - Heat Transfer - Radiation
Heat transfer from one object to another through emitted thermal energy in the form of electromagnetic waves.
Infrared radiation is the primary mechanism by which thermal cameras measure temperature.
Infrared (IR) radiation was first detected by William Herschel in 1800.
Thermography - Review of the Definition
Thermography is: “The use of radiant heat emitted by a body to construct images of temperatures.”
Viewing heat in the form of infrared radiation.
Emitted from an object (such as a wall).
The camera is turning this information into an image of measurable temperatures.
All objects in the world emit heat in the form of infrared radiation.
Thermography - Temperature
Temperature is one of the most common methods of measurement.
A good indicator of performance:
If a machine is running too hot, then it may indicate imminent failure.
Our body temperature will rise if we are feeling unwell.
For buildings in particular:
Heat loss = Increased energy use = Increased cost to user/Risk of fuel poverty/Harm to the planet.
Thermography - Heat loss in buildings
Common causes of heat loss in buildings:
Cracks.
Condensation and mould.
Poor/missing/damaged insulation.
Draughty windows.
However, some defects are hard to detect using visual and non-destructive measures.
