Types of Test Chamber Cooling System
Types of Test Chamber Cooling SystemThere are two major types of chamber cooling systems, expendable refrigerants and mechanically cooled.Expendable RefrigerantsExpendable refrigerants are liquid/gases that can be injected directly into the space being cooled or into heatexchangers, similar to mechanical systems. As the liquid enters the chamber (directly or through a fin coil) itabsorbs heat and flashes to a gas. The gas is then vented out of the chamber and should be ducted outdoors.The two most popular refrigerants are liquid nitrogen (LN2) and liquid carbon dioxide (CO2). Cryogenictemperatures down to - 184˚C can be achieved with LN2. CO2 on the other hand can only achievetemperature down to -68˚C. Both of these gases are environmental safe andcan be vented to the atmosphere. Note: it is imperative that the gases be ventedoutdoors. These gases displace oxygen and asphyxia can occur if the chamber is notproperly vented.Mechanically cooledMechanically-cooled refrigeration systems are fundamentally the same as those usedin home refrigerators. They utilize a compressor and circulate a refrigerant around aclosed loop system. The ultimate low temperature required by your testingdetermines the type of refrigeration system needed.Single StageSingle-stage refrigeration systems typically can pull the temperature in the chamber down to - 34˚C.Some manufacturers rate their single stage systems down to -40˚C. However, due to the refrigerant usedthere is very little cooling capacity available at -40˚C and can be difficult to achieve. For continuous operation at-40˚C and below most manufacturers recommend a cascade refrigeration system.CascadeCascade refrigeration systems have two separate refrigeration systems working to cool the chamber down to anultimate low of -73˚C and -85˚C on industrial freezer models. The first stage refrigeration system coolsand condenses the refrigerant in the second stage. The second stage refrigerant flows through an evaporatorlocated in the chamber which cools the air. These systems can become very complex depending on yourapplication.