Talking about Data Center Cooling Technology
The rapid growth of data center construction has led to more and more equipment in the computer room, which provides a constant temperature and humidity cooling environment for the data center.
The power consumption of the data center will greatly increase, followed by a proportional increase in cooling systems, power distribution systems, UPS and generators, which poses a major challenge to the energy consumption of the data center.
At a time when the whole country is advocating energy conservation and emission reduction, if data centers blindly consume social energy, they will inevitably attract the attention of the government and people. Not only is it not conducive to the future development of data centers, but also runs counter to social morality, so energy consumption has become the most concerned content of data center construction.
In order to develop a data center, it is necessary to continuously expand its scale and inevitably increase equipment. This cannot be reduced, but the utilization of equipment needs to be improved. Another big part of energy consumption is heat dissipation. The energy consumption of a data center air conditioning system accounts for almost one-third of the energy consumption of the entire data center. If you can work harder on this, the energy saving effect of the data center will be improved. Immediately. So, what cooling technologies are available in the data center, and which are the future development directions? The answer will be found in this article.
Air cooling system
The air-cooled direct expansion system becomes an air-cooled system. In the air-cooled system, half of the refrigerant circulation loop is located in the data center computer room air conditioner, and the rest is located in the outdoor air-cooled condenser. The heat inside the machine room is squeezed into the outdoor environment through the pipeline that uses the refrigerant to circulate. The hot air transfers the heat to the evaporator coil, and then to the refrigerant. The high temperature and high pressure refrigerant is sent to the outdoors by the compressor The condenser, and then radiate the heat to the outdoor atmosphere. The air-cooling system has relatively low energy efficiency and directly dissipates heat by the wind. From a cooling perspective, the main energy consumption is generated by the compressor, indoor fan, and air-cooled outdoor condenser. Due to the centralized layout of the outdoor units, when the outdoor units are all turned on in summer, the phenomenon of local heat accumulation is obvious, which will reduce the cooling efficiency and affect the use effect. Moreover, the noise of the air-cooled outdoor unit has a greater impact on the surrounding environment, and is prone to impact on surrounding residents. Natural cooling cannot be used, and energy saving is relatively low. Although the air-cooling system has low heat dissipation efficiency and high energy consumption, it is still the most widely used heat dissipation method in data centers.
Liquid cooling system
Air-cooled systems have their inevitable shortcomings. Some data centers have begun to switch to liquid cooling, and the most common is water-cooled systems. The water cooling system removes the heat through plate exchange, and the refrigeration is stable. An outdoor cooling tower or dry cooler is needed to replace the condenser for heat exchange. The water cooling eliminates the air-cooled outdoor unit, which solves the noise problem and has a small impact on the environment. The water cooling system is more complex, costly, and difficult to maintain, but it can meet the cooling and energy-saving requirements of large data centers. In addition to water cooling, there is oil cooling. Compared with water cooling, oil cooling system can further reduce energy consumption. If the oil cooling system is adopted, the dust problem faced by traditional air cooling will no longer exist, and the energy consumption will be much lower. Unlike water, oil is a non-polar substance, which will not affect the electronic integrated circuit and will not damage the internal hardware of the server. However, liquid cooling systems have always been thunderous and rainy in the market, and few data centers will adopt this method. Because the liquid cooling system, whether it is immersion or other methods, requires the liquid to be filtered to avoid problems such as the accumulation of contaminants, excessive sediments and biological growth. For water-based systems, such as those liquid cooling systems that use cooling towers or evaporation, etc., in a given volume, it is necessary to deal with the sediment problem along with the removal of steam, and it needs to be separated and "drained" for disposal, even then The treatment of this may cause environmental problems. Evaporative or adiabatic cooling system.
Evaporative cooling technology is a method of cooling air by using a drop in temperature. When water encounters flowing hot air, it begins to vaporize and turn into gas. Evaporative heat dissipation is not suitable for refrigerants that are harmful to the environment, and the installation cost is low. It does not require the use of traditional compressors, has low energy consumption, and has the advantages of energy saving, environmental protection, economy and improvement of indoor air quality. The evaporative cooler is a large fan that draws hot air onto the wet water pad. When the water in the wet pad evaporates, the air is cooled and pushed out. The temperature can be controlled by adjusting the airflow of the cooler. Adiabatic cooling means that during the process of adiabatic rise of air, the air pressure decreases with the increase in height, and the air block does work externally due to its volume expansion, which leads to a decrease in the temperature of the air itself. For the data center, these cooling methods are still novel.
Closed cooling system
The radiator cover of the closed cooling system is sealed and an expansion tank is added. During operation, the coolant vapor enters the expansion tank and flows back to the radiator after cooling, which can prevent a large amount of evaporation loss of the coolant and increase the boiling point temperature of the coolant. The closed cooling system can ensure that the engine does not need to add cooling water for 1 to 2 years. In use, the seal must be ensured in order to receive the effect. The coolant in the expansion tank cannot be filled up, leaving room for expansion. After two years of use, it will be discharged and filtered, and the composition and freezing point will be adjusted before continuing to use. Enclosed means that the air flow is insufficient, which can easily cause local overheating problems. Closed cooling is often combined with water cooling or liquid cooling, and the water cooling system can also be made into a closed system, which can more effectively dissipate heat and improve cooling efficiency.
In addition to the heat dissipation methods described above, there are many wonderful heat dissipation methods, and some have even been put into practical use. For example, using natural heat dissipation, the data center is built in cold Nordic countries or built to the seabed, and the equipment in the data center is cooled through "extremely deep cold". Like the data center built by Facebook in Iceland, Microsoft is building a data center under the sea. In addition, water cooling can be used without standard water, sea water, domestic wastewater or even hot water can be used to dissipate heat for the data center. For example, Alibaba uses the water of Thousand Island Lake for heat dissipation. Google has established a data center in Hamina, Finland that uses sea water for heat dissipation. eBay built its data center in the desert. The average outdoor temperature of the data center is about 46 degrees Celsius. .
The above introduces the commonly used technologies for data center cooling, some of which are still in the process of continuous improvement and are still laboratory technologies. For the future trend of data center heat dissipation, in addition to high-performance computing centers and other Internet-based data centers, most data centers will be moved to places with lower prices and lower power costs. By adopting more advanced heat dissipation technologies, Further reduce data center operation and maintenance costs and improve energy efficiency.
