How Do Environmental Test Chambers Work?: Environmental Test Chambers

How Do Environmental Test Chambers Work?

For those of you unfamiliar with the term, environmental test chambers are systems that allow a user to control the environmental conditions inside an enclosed space in order to run controlled tests on a subject. Chambers can run in size from half a cubic foot (which comfortable sit on a bench) to 12,000 cubic foot (which form complete drive-in rooms). The environmental conditions that can be recreated vary, from temperature and humidity to corrosion.

But how do these chambers work?
In terms of temperature and humidity conditions, these chambers utilise electric heaters to create temperature and refrigeration systems. This cools or removes temperature from the environment.

Refrigeration systems can be either mechanical or a liquid cooling based system – there are advantages and disadvantages to each option.

To introduce humidity, steam generators are utilised; to remove humidity, a mechanical dehumidifying system is used. To boost the humidity range of the chamber and allow it to reach a lower relative humidity, air dryers can be added.

To create salt spray that mimics sea spray, a salt solution is prepared and stored in the tank. Compressed air is used to force it through a nozzle, creating a mist inside the chamber.

Is this all that we need to be aware of?
Delving deeper, there are multiple types of temperature testing and different environmental test chambers have been built to accommodate them.

Steady state testing means that the chamber holds the environment at a certain temperature (and humidity, if necessary) for a long period of time. Chambers built for this type of testing have a high temperature control to ensure that the results are as accurate as possible.

Thermal cycling testing means that the chamber cycles from a selected temperature to another, focusing on the ramp rate that it takes to reach those temperature levels.

Thermal shock testing means that a product is quickly exposed to drastically different temperatures. This allows you to test for product failures, as well as testing the product’s ability to cope with different climatic zones.

Thermal cycling versus thermal shock
These types of temperature testing might be similar in name, but they’re very different in their actual procedures. Both thermal cycling and thermal shock testing require a product to be brought to two different temperature extremes, but where they differ is the time taken to reach those temperatures.

Thermal cycling is a slower process – the product is brought to two temperature extremes over a period of time. The biggest factors of such tests are the ramp rates of the chamber to the temperature extremes. The ramp rate is important because it’s what applies the level of stress. This process also has long soak periods – the product is left at a certain temperature to “soak” in that condition.

Thermal shock testing, on the other hand, is much quicker. Multi compartment chambers have two or three zones – one is the upper temperature limit, the next is the lower temperature limit and the last can be added for ambient temperature exposure. A basket is used to quickly transfer the product between the zones, which allows for it to be taken immediately between extremes.

The biggest factor in this type of testing is the recovery time.

Salt spray testing
Salt spray environmental test chambers are used to test a product’s corrosive properties. It is primarily used to test how well finishes, paints and other products can last when exposed to real world situations – you can see years of corrosive exposure in just a short amount of time.

The chambers hold the internal testing environment at a constant temperature, whereas the salt and spray is generated using compressed air to create a pressure differential in the nozzle.

Simultech is a leading supplier of environmental simulation equipment to various industries across Australia. Our product range covers test chambers, heat technology (drying cabinet, industrial drying ovens) and solar instruments (photoVoltaic, pyranometer, spectroradiometer etc.)