To be comfortable in using an infrared camera you must be very familiar with the three modes of heat transfer: conduction, convection, and thermal radiation. I’ll use the glossary of the ASNT Nondestructive Testing HANDBOOK, Volume 3 Infrared and Thermal Testing to define these three modes. Conduction is defined as: “Heat transfer occurring when more energetic particles collide with – and thus impart some of their heat energy to – adjacent less energetic (slower moving) particles. This action is passed on from one atom (or free electron) to the next in the direction of cooler regions. Thus, heat always flows from a warmer to a cooler region.” Convection is defined as: “Type of heat transfer that takes place in a moving medium and is almost always associated with transfer between a solid (surface) and a moving fluid (such as air), whereby energy is transferred from higher temperature sites to lower temperature sites.” Thermal radiation is defined as: “Mode of heat flow that occurs by emission and absorption of electromagnetic radiation, propagating at the speed of light and, unlike conductive and convective heat flow, capable of propagating across a vacuum; the form of heat transfer that allows infrared thermography to work because infrared energy travels from the target to the detector by radiation.”
The following infrared images were taken with Fluke IR cameras and they demonstrate very nicely what missing insulation looks like, both in the summer and winter. All three modes of heat transfer are taking place in both of these images. Of course you will always see IR radiation no matter what the situation. All surfaces emit infrared energy waves. In the first image we see a ceiling bay that is transferring a lot of heat into the room. This image was taken in the cooling season where the heat source is outside. So, the heat transfer is from outside to inside. In an uninsulated bay (the red area in the 1st image) two modes of heat transfer are occurring: (1) convection and (2) IR radiation. In a properly insulated bay (the blue area in 1st image) the mode of heat transfer is conduction. The purpose of insulation is to slow down conductive heat transfer. In the second image, which was taken in the heating season, we are looking at a loss of heat (blue area in 2nd image) due to a lack of insulation. Again, we have convection and IR radiation. The warm areas are insulated areas where conductive heat transfer is being “resisted” (R-factor).
It’s important to slow down and think on a molecular level. Identify the mode or modes of heat transfer and see the movement of heat (thermo – dynamics).
How’s your comfort level in thermography?
(The above comments represent my opinion).
Rod Hoff / Restoration Consultants Inc
Thermography Instructor / IR camera sales
3284 Ramos Circle, Sacramento CA 95827
toll free 888-617-3266 ext 301
Provider of Fluke TiS, TiR, TiR1, Ti, Ti25, TiR27, Ti27, TiR29, Ti29, TiR32, Ti32, TiR3, and TiR4 infrared cameras.
See DEMO www.moistureview.com/demo.html