Inside an Environmental test chamber

To achieve a set level of temperature the chamber must be able to both heat and cool to achieve and control at the desired level.

Heating – this is done using electrical heating elements sized accordingly to the chamber specification and positioned in the airflow to give even distribution and uniformity.

Cooling – this is done using a mechanical cooling system with close loop control. The main parts of a single stage cooling system are compressor, condenser, expansion valve, solenoid valves and cooling coil (Evaporator). Evaporators are sized to achieve a specific cooling duty and are generally located in a conditioning plenum to give even distribution into the test area. A single stage system will achieve temperatures down to -40°C.

A cascade system is a two stage cooling system and has the addition of a second compressor. The system uses two refrigerants, one type for the first stage and another for the second stage. A cascade system will achieve temperatures down to -65°C.

To achieve a set level of humidity the chamber must be able to both humidify and dehumidify in order to achieve and control at the desired level.

Humidity – this is done by introducing steam into the test area, the steam is generated outside the test area and is pulsed into the conditioning plenum in a controlled manner.

Dehumidity – this is done by creating a controlled cold surface using the main refrigeration cooling system, moisture from the turbulent airflow is then condensed on to this cold surface.