Thermal Testing

Heat leakage's of insulated containers, trailers, vehicles, or cabinets can be determined in the CRT environmental test chambers. For this test, the environmental chamber air is maintained at a constant temperature in the range 0 C to +10 C.

A metered quantity of electrical heat is fed continuously into the insulated test unit to maintain the internal temperature at least 20 C above the chamber temperature.

Once stable conditions are established, mean internal and mean external temperatures are calculated from twelve temperature sensors around and twelve inside the test unit. Dividing the measured heat input by the mean temperature difference determines the thermal heat leakage, which is calculated in W/k. Effectively Watts of energy for each °C of temperature difference.

If the thermal value is required a “U” value, then the root mean area of the test unit is calculated from measurement of external and internal length, width and height.

The overall heat transfer coefficient in W/m/k is calculated from the thermal heat leakage divided by the root mean area. CRT offers thermal tests to ATP, BS EN1496 part 2 and our own cost effective quick test known as the “Cambridge K test.”

Thermography

If further analysis of the structure is required to try to determine where the weakness in the thermal insulation envelope actually is, then CRT can carry out a thermal imaging investigation.

Infrared thermography is a detection procedure using a special camera that converts heat energy invisible to the naked eye into a visible picture. IR cameras provide a non-contact means to study the thermal properties of components while under load. This can be useful in detecting weak areas of insulation caused by thermal bridging, missing foam, delamination and water ingress.

Especial benefit is obtained when investigating container thermal properties in conjunction to our test chamber as with the stable temperature achievable it is easy to determine the weaknesses.

In the photographs given below, in a recent investigation on a refrigerated truck, the wheel arch of a refrigerated vehicle is shown, leaking so much heat it is actually illuminating the wheel.