With the development of society and the process of digitization, the demand for data centers is increasing. Data centers accounted for about 2.7 percent of society's total electricity consumption in 2020, according to an industry white paper. According to incomplete statistics, the energy consumption of refrigeration in most data centers currently in operation has accounted for about 45% of the energy consumption of data center room.

Cold source can be generally divided into direct expansion air cooling source, freezing main engine cooling source, natural cooling cold source.

Air-cooled precision air conditioners generally use scroll compressors for refrigeration (generally installed in precision air conditioners). The energy efficiency ratio is relatively low, which is generally between 1.5 and 3 in Beijing area (low in summer, high in winter). Air-cooled precision air conditioners are generally suitable for use in small data centers.

Centrifugal water-cooled air conditioning system is the preferred solution of the new generation of large data centers, which is characterized by large cooling capacity and high energy efficiency ratio of the whole system (generally between 3 and 6). Centrifugal refrigerating unit in small load (generally less than 20% of the full load) prone to surge, can not operate normally. Therefore, a small screw type water cooling unit or air cooled water cooling unit is usually installed as a transition in the design of water cooled air conditioning system in data centers.

Free cooling technology refers to the whole or part of the use of natural free cold source refrigeration to reduce the energy consumption of the compressor or freezer. In the cold weather or low temperature for a long time area is very suitable for the use of free refrigeration technology. Air cooling natural cooling is one of the commonly used free cold sources. In winter or spring and autumn, outdoor air is directly sent into the room after filtration as a cold source. This kind of natural cooling method is simple in principle and low in cost.

Water cooling air conditioning system + free cold technology, when the outdoor environment temperature is low, you can close the refrigeration unit, the use of plate heat exchanger for heat exchange, known as water cooling natural cooling. This reduces the time to turn on the cooling machine, reducing a lot of energy consumption. The wet bulb temperature below 4℃ can satisfy the complete natural cooling, and the wet bulb temperature between 4 and 10℃ can achieve partial natural cooling.