Data Center Cooling System

There are various forms of refrigeration in data centers, which are classified according to different dimensions. The refrigeration systems commonly used in data centers are: fluorine refrigeration system, water refrigeration system, and air refrigeration system.

There are two main types of fluorine refrigeration systems: air-cooled fluorine pump system and glacier phase change system. The air-cooled fluorine pump system has mature and stable technology and has a wide range of application scenarios in the data center field. The glacier phase change system combines the advantages of the fluorine pump system based on technological iteration and reduces the resistance loss of the equipment to further improve the energy efficiency of the equipment.

Air-cooled fluorine pump system: composed of compressor, condenser, circulation pump, expansion valve and other components. It has two modes: compression refrigeration and fluorine pump circulation refrigeration. When the outdoor ambient temperature is lower than the system control set point, the compressor in the air-cooled air conditioning system will stop working and be replaced by a fluorine pump. At this time, the refrigerant after the heat exchange between the evaporator and the indoor air will directly enter the air-cooled condenser to exchange heat with the outdoor cold source and cool it into a liquid state. Under the action of the fluorine pump, the liquid refrigerant overcomes the tube resistance and returns to the evaporator to continue heat exchange, thereby achieving energy saving effects. In short, when the outdoor ambient temperature is lower than the set point, the air-cooled air-conditioning system will use a fluorine pump instead of the compressor for refrigeration, thereby achieving better energy-saving effects.

Glacier phase change system: In recent years, with the continuous updating and iteration of technology, technology has developed. On the basis of fluorine pump air conditioning technology, it adopts evaporation and condensation, magnetic levitation compressor, natural cooling, power heat pipe and other technologies. The glacier phase change system has the advantages of being widely used in water-scarce areas, high system energy efficiency, and long free cooling time.

Water cooling system technology is mature and widely used in medium and large data centers. Compared with traditional air cooling technology, it has higher energy efficiency and better stability of equipment and systems. This article mainly introduces two systems: air-cooled cold water system and water-cooled cold water system.

Air-cooled cold water system: uses air cooling to cool the refrigerant in the condenser through a fan, directly expelling heat into the air for cooling. Compared with the water-cooled chilled water system, it does not need to be equipped with cooling towers, cooling water pumps, pipelines and other components, and can ensure the normal operation of equipment refrigeration in water shortage environments. Air-cooled chilled water systems are simple, reliable, and easy to maintain, so they are widely used in medium and large data centers.

Water-cooled chilled water system: The system uses large refrigerated water chiller equipment equipped with plate exchangers, cooling towers, water pump pipelines and other components. It uses water pump circulation power to overcome the resistance in the pipes. It is also equipped with pools and cold storage tanks to ensure water replenishment and cold storage in the data center. The heat in the computer room is transferred to the plate exchanger/cooler through the chilled water through the heat exchange of the precision air conditioner. The cooling water carries the heat to the cooling tower and transmits it to the outdoors. Natural cooling of water-cooled chillers generally involves adding a plate heat exchanger between the cooling water and chilled water circuits. When the outdoor temperature is low, the chiller is shut down and low-temperature cooling water is directly used as a cold source to cool the cold water circuit through the heat exchanger.

The air cooling system mainly introduces the indirect evaporative cooling system. Currently, the financial industry is gradually adopting and trying to use the indirect evaporative cooling system to meet the overall energy consumption indicator supervision of the data center. An air-to-air heat exchanger is used to realize heat exchange between indoor air and outdoor air, and at the same time, the outdoor wet bulb temperature can be reduced through spray evaporation. When air heat exchange cannot meet the cooling capacity demand, the equipment turns on mechanical refrigeration. Compared with the traditional water cooling system, the heat exchange link is reduced and the heat exchange efficiency is further improved. Indirect evaporative cooling has the characteristics of no terminal equipment indoors and can be widely used in areas with superior natural conditions.

Through a comprehensive comparative analysis of the refrigeration system in terms of power consumption, water consumption, technology maturity and operation and maintenance difficulty, the data center architecture design is adapted. It is necessary to consider the surrounding environment, water resources, power resources of the project location and whether the construction party’s technology is widely adopted in the industry.

Summarize

The data center cooling system is a complex system engineering that requires comprehensive consideration of multiple factors for design and optimization. Through reasonable refrigeration method selection, system design, maintenance and other measures, we can ensure the stable supply of cold sources and efficient management of the equipment environment in the data center.

As the demand for computing power increases, the power and energy consumption of single cabinets have increased. Traditional air cooling has gradually been unable to meet the efficient heat dissipation requirements brought about by the increase in computing power in supercomputing centers. The advantages of liquid cooling technology have become increasingly obvious.