The data center is generally a large warehouse, which mainly stores the server and other computer devices connected to the Internet. These devices save most of the data on the Internet, and provide the computing power for cloud computing. It can be expected that the data center will generate a lot of heat, it is reported that its energy density is more than 100 times that of an ordinary office building.
Data centers and equipment internal thermal load must be effectively managed, in order to cool the data center, the data center has taken various measures. So, what is the development of cooling technology in data center? Which cooling methods are most favored by the manufacturers?
Natural cooling, using only the temperature difference between the external air temperature and the equipment to cool the equipment, is one of the earliest cooling schemes in the data center, but this cooling method is restricted by the area, so the data center usually uses some form of air conditioning to cool the IT.
The air-conditioning equipment used for cooling the data center has also experienced a period of development. From the early ordinary air conditioning to the 70s precision air conditioning, the air cooling has been developing faster because of the low cost, but as the equipment continues to increase, the server is more and more dense, and the air cooling is gradually unable to fill the cooling demand, and availability and green energy saving. Dynamic cooling has become the main direction of innovation. Liquid cooling technology is favored by many manufacturers because of its outstanding performance.
Liquid cooling refers to the replacement of air by liquid to take away the heat generated by CPU, memory strip, chipset, expansion card and other devices in operation. According to the current technological research process, liquid cooling is classified as water cooling and refrigerant cooling. The refrigerants available include water, mineral oil, electronic fluoride solution, etc. According to the cooling principle, the liquid cooling is divided into two systems: cold plate liquid cooling (indirect cooling) and submerged liquid cooling (direct cooling).
If the previous air cooling is to let the server blow the fan, then the liquid cooling is to allow the server to shower or bathe. At present, there are three main liquid cooling technologies in the industry: cold plate, spray and immersion.
Cold plate liquid cooling is the flow of cooling water from the special water injection port, through the closed heat pipe flow into the main engine, take away the heat of CPU, memory and hard disk and other components out.
Spray type liquid cooling means to retrofit IT equipment, deploy corresponding spray devices, and cool the overheated devices when the equipment is running.
In contrast, submerged liquid cooling is more special. It is understood that the heat dissipation effect of immersion liquid cooling technology is first appeared abroad. It can be understood as making the server in the liquid, although it can achieve high density, low noise, low heat transfer temperature difference, natural cooling and so on. But the immersion liquid cooling technology is very difficult and cost high. At present, the industry only has single machine test and single machine. It is shown that server cluster deployment is not yet available.
In fact, the concept of liquid cooling has appeared many years ago, but it has only arisen in recent years. This is mainly because with the rapid development of the data center industry, especially the deployment of high density and even ultra-high density servers, the challenges facing the data center refrigeration are increasingly severe. How to further reduce the high power consumption, how to achieve the green development of the data center while guaranteeing the performance, has become the concern of the industry. And the focus of the breakthrough.
At present, the mainstream manufacturers at home and abroad are vigorously promoting the research of liquid cooling technology. For example, Facebook is launching a new indirect cooling system, the StatePoint liquid cooling (SPLC) solution, developed in collaboration with the Nortek air solutions company. Since it was developed in 2015, the technology (Nortek patent) uses a liquid air heat exchanger, cooling water through membrane separation layer evaporation technology, and cooling the air in a data center facility with cold water, and the diaphragm can prevent cross contamination between water and air.
In addition, the spray cooling data center, which is the core of the combined liquid cooling technology, is a new liquid cooling method, which is different from the traditional air cooling and soaking cooling mode. It directly sprinkled the insulated liquid cooling medium into the heating device inside the server or the radiator with its contact, and the cooling fluid was absorbed quickly. The heat of the chip is transmitted through the liquid cooling system to the outdoor atmosphere, which not only solves the problem of low air cooling efficiency, but also solves the problem of high cost of soaking and maintenance.
According to the industry news, the liquid cooling scheme is rising, with the technology driven by AI and the network edge computing, and also the decline of the data center reduction. At present, more and more manufacturers use liquid cooling technology to cool down the data center. For example, Google I/O 2018 first introduced liquid cooling in Data Center for cooling of AI chips.
Innovation is the first driving force to lead the development of science and technology. As a kind of efficient, energy-saving and safe cooling technology, liquid cooling technology is becoming the inevitable choice of most data centers.
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