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How does a precision air conditioner work?

Precision air conditioner (precision cooling) is used to control the temperature and humidity to precision level for mission-critical environments such as data centers, hospitals, laboratories. Unlike house air conditioners, which are designed to cool people,precision cooling cools IT equipment. As a result, they must operate 24 hours a day, 365 days a year. So how do precision air conditioners work?

how does a precision air conditioner work

The working principle of PAC

Precision air conditioners do not work by creating cold air. They work by removing the heated air
In the room and transfer it outside. Before digging into the working principle of precision air conditioners. You need to know the truth: Fusion, vaporization, and sublimation are endothermic processes, whereas freezing, condensation, and deposition are exothermic processes. Here are the components of the PAC system:


PAC systems work step by step as below:

Step 1: Heat is absorbed by the evaporator coil
The warm air inside your room is drawn in through a vent and blows over the cold evaporator coil. As the refrigerant absorbs the heat from the passing air, it changes from a liquid state to a gaseous state and continues to travel along with the loop system toward the compressor.

Step 2: Compressor compresses refrigerant
The compressor decreases the gas’ volume. Usually this is done by squeezing the gas tightly between two solid objects. This raises the pressure and temperature of the refrigerant, preparing it for the condensing process.

Step 3: Heat is transferred to the outside
The refrigerant, now a superheated vapor, reaches the condenser (which is located outdoors) and is exposed to the outside air. The outside air absorbs the heat from the refrigerant, lowering the temperature of the refrigerant and changing the state from a gas back into a liquid.

Step 4: Refrigerant gets cold; process repeats
Once the heat from the refrigerant is removed to the outdoors, the cold refrigerant travels back indoors to the evaporator to repeat the process over again. The process continues until the inside temperature of your room reaches you set temperature.

There are different types of precision cooling technology such as air-cool, free cooling, dual cool, chilled water and refrigerants R410A and R407C. They share a similar working process but use a different medium to transport heat generated inside the data center to the outside environment. 
For example, the chilled-water type precision air conditioner uses water, instead of refrigerant to cool the space. AC unit inside the data center transfers the heat generated by IT equipment to chilled water. The water gets hot and the room gets cold.

Further reading about precision air conditioner: