Insulation of Commercial Walk-in Freezers Checked with Thermal Imaging
Enterprises that need to store large amounts of goods at temperatures well below the freezing point of water often install large walk-in freezers on their premises. These large freezers are capable of keeping entire rooms full of these goods, usually foodstuffs, at very low temperatures.
There is just one downside, cooling requires a lot of energy so it is very important that no outside heat leaks in. To make sure that the insulation of the freezers is working properly, thermographers inspect the insulation material with thermal imaging cameras. In essence, inspecting walk-in freezers, cold rooms and other types of large commercial refrigeration units is very similar to building insulation inspections, the only difference is the direction of the heat. Building insulation inspections generally try to detect heat leaking from the inside of the building to the outside air. With refrigeration units we want to detect heat leaking inwards, but the mechanism of heat leakage is just the same.
Case Example
A thermography consultant is called out to Leeuwarden to inspect two walk-in freezers. Any heat leakage can cause huge unnecessary expenditure on energy bills, so detecting these heat leaks at an early stage allows the owner to fix the insulation defects and prevent soaring energy bills. With the continuously rising energy prices the demand for walk-in refrigerator and freezer inspections is also growing. “This particular freezer which I’m inspecting at the moment seems to be very well insulated, but you’d be surprised to see how often newly built refrigeration units have a faulty construction. Sometimes the joints between the insulation panels are not protected properly which creates heat bridges causing lots of unnecessary energy consumption. In other cases older units might develop insulation faults over time due to wear. In both scenarios the best way to detect these insulation defects is by using thermal imaging cameras. Other methods, like spot pyrometers and such, really are not an option in this type of inspection as it is simply too easy to miss problems that can be relatively easily detect using thermal imaging.”
Thermal image shows an example of improperly connected joints between insulation panels, causing heat leakage.
Tools
The FLIR P640 thermal imaging camera has an image resolution of 640x480, thermal sensitivity of 30 mK (0.03 °C) and an accuracy of ± 2 °C or ± 2 % of the reading, This means that the camera is capable of producing high-quality thermal images which are needed in order to draw the right conclusions.
Another important thermal imaging camera feature for this particular application is the calibration range. The camera is calibrated to a minimum temperature of – 40 °C which is very important to allow accurate temperature measurements. Most freezers are kept at temperatures between –20 °C and –30 °C but some exceptionally cold freezers cool their contents down to –50 °C or even –60 °C. Even at temperatures below the official calibration range, thermal imaging cameras are still capable of visualizing insulation leaks.
The Importance of Training
A good camera is just half of the solution, the knowledge and skills of the thermographer are just as important. It is important that inspectors have at least a level I thermography and preferably level II certificate from the Infrared Training Center (ITC).
The cameras are used for a wide variety of applications, including inspections of building insulation, industrial maintenance inspections, HVAC systems, airplane composite materials water ingress and refrigeration unit insulation inspections.
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