As the computing power and power consumption of new generations of computer equipment have increased significantly, how to increase the power density per cabinet in traditional data centers has become increasingly important. Intel's research shows that the same computing power required 25 cabinets and 128KW of energy consumption (5.1KW / per cabinet) in 2002, but only one cabinet and 21KW of energy consumption (21KW / per cabinet) in 2008 . In contrast, we saved 107KW of energy consumption, and also greatly saved the physical size and structure of the data center.
This substantial increase in computing power is mainly due to the rapid development of virtual computing, memory systems, multi-core CPU systems, CPU speed and GPGPU technology. Virtual computing greatly improves the efficiency of the server, thereby directly increasing the heat density of a single cabinet. With the rapid development of memory capacity and speed, the latest DRAM technology is that the calorific value of memory has also been greatly improved. Applications such as engineering and scientific research make extensive use of graphics floating-point operations. GPGPU increases the heat output of graphics cards from 25W to more than 300W. Although the power consumption of servers continues to increase, the performance and power consumption ratios continue to decline. As can be seen from the above example, if the data center air-conditioning system can efficiently cool the cabinet, we will greatly reduce the total energy consumption of the data center, so that in essence we can really have a green data center.
Improving the cooling efficiency of air conditioners and saving energy are only an important part of data center management. However, the increasing heat density of each cabinet brings us more challenges. At present, the average heat density of each cabinet in the global data center is about 6.5KW, but ASHRAE2 predicts that the average cooling capacity of each cabinet in the data center in 2014 is 37KW. This leap in heat density of 5 times requires our continuous innovation in the data center to solve. This article will discuss the current series of technological innovations and evaluate the advantages and disadvantages of various solutions
Physical isolation of hot and cold air (baseline)
Studies have shown that in an unreasonably designed data center, 60% of the cold air supply of air conditioners is wasted due to the unreasonable air flow organization. At present, the traditional open hot aisle structure data center is facing two major airflow management problems: the mixing of cold and hot air and the waste of air conditioning and cold air supply. These two phenomena greatly reduce the efficiency of air conditioning and refrigeration. Among them, the mixing of hot and cold air refers to the mixing of hot air generated by the equipment and the cold air supply of the air conditioner to increase the air inlet temperature of the equipment; the waste of the cold air supply of the air conditioner refers to the The cold air supply does not enter the equipment, and it cools the equipment and returns directly to the air conditioner. The mixing of hot and cold air is also the main reason for the temperature inconsistency in the data center, and this phenomenon also greatly reduces the cooling efficiency and capacity of the data center air conditioner. How to solve these two phenomena is actually the simplest and most effective method is to physically separate the hot and cold air.
Intel3 years of research and experiments have shown that good air distribution management can greatly reduce the mixing of cold and hot air and the waste of air conditioning cold air supply. The heat density of Intel's current data center has also increased from 310WPSF to 781WPSF in a single cabinet (15kW per cabinet increased to more than 40kW). In addition, Dell4 and HP5 data centers are also using cold or hot pool technology. Using cold pool or hot pool technology, the cooling capacity of the data center air conditioner only needs to meet the cooling capacity of the equipment. However, this technology also has certain limitations, which will be discussed in detail below.
Cold pool and hot pool
Hot aisle closure or hot pool (HAC) is to seal the hot aisle and return the hot return air to the data center air conditioning system through the return air pipe (as shown in Figure 1). Compared with the hot pool, the cold pool (CAC) is to seal the cold aisle. Both of these technologies isolate the cold air supply and the hot return air of the air conditioner, and increase the return air temperature of the air conditioner to improve the cooling efficiency of the air conditioner. The difference between these two methods is mainly scalability, thermal management and the suitability of the working environment.
The scalability of the cold pool is mainly limited by the under-floor air supply and how to send the under-floor cold air into multiple cold pools. At present, there are many misunderstandings about this technology in the world. Many people think that as long as the air output of the air conditioner can meet the cooling air volume of the device. But they ignored the pressure drop and space limitations of the cold air supply under the raised floor for multiple cold pools. In contrast, the hot pool uses the entire data center as a cold aisle to solve this problem, because it expands the space of the cold aisle. In this way, the hot pool has more air conditioning redundancy than the cold pool, and the extra hot aisle space will provide a few minutes of valuable repair time when the air conditioning system fails. Finally, with the improvement of the heat dissipation capacity of the server equipment, the heat dissipation air volume required by the server will be greatly reduced. Now the temperature of the hot air of many servers can reach 55oC. The temperature of the unisolated part of the cold pool will be much higher than that of the traditional data center, which will greatly increase the comfort of the data center staff and reduce the service life of other data center equipment. In summary, although these two methods can greatly increase the heat density of each cabinet, when the heat pool is used reasonably, the efficiency of the heat pool should be much more effective and reliable than that of the cold pool.
Through the above comparison, we can find that the hot pool has more advantages than the cold pool. On this basis, we talk about two different heat pool schemes: fully enclosed heat pool and partially enclosed heat pool. Fully enclosed heat pool is to send all the hot return air back to the air conditioning system. Chimney cabinets and rigid wall isolation hot aisles are two different solutions. In the partially enclosed heat pool, the gaps and spaces in the enclosed material will greatly waste the air volume of the cooling air supply to the equipment. Usually some of the enclosed heat pools we see include rigid or soft materials to seal the heat channels. The use of fully enclosed heat pools can greatly increase the heat density of each cabinet, but there are often reasons such as construction budget and site restrictions that cannot be achieved. When we can not achieve a fully enclosed heat pool, we can use rigid or soft baffles and other objects to maximize the sealing of the heat channel, so that although we can not completely eliminate the hot return air return and cold air supply waste like the fully enclosed system Phenomenon, but we sealed up a lot of hot return air. In data centers that use partially enclosed heat pools, hot spots in the data center may still exist, and the location of fire protection facilities also needs additional attention, but we can greatly increase the heat density of each cabinet compared to traditional data centers. However, to reach the heat density of 37KW per cabinet in 2014, these are far from enough.
In-Row Cooling Solution
When the data center uses a fully enclosed system, another solution is In-row Cooling. Precise matching refrigeration also requires a closed side panel to isolate hot and cold air. The advantage of accurate matching cooling is that the data center does not require expensive floors or ceilings, and the cooling unit is much closer to the server equipment, which reduces the air supply path. But the biggest disadvantage of this scheme is that the small refrigeration system is not as efficient as the large refrigeration system. Table 1 is a comparison table of the supply air volume and energy consumption of the four frequency conversion refrigeration systems of Delta Electronics 6. The comparison table clearly shows that under the same working wind pressure, the air supply volume and energy consumption ratio of the large refrigeration system are smaller, which means that it is more effective and energy-saving than the small refrigeration system. In addition, we must also face various challenges such as: the redundancy of accurate matching refrigeration, the inability to use air economizers, the need for a large amount of installation space and the leakage of cooling water, etc. Accurate matching refrigeration is a fully enclosed system, but data center managers must have good preparation and analysis when using the system.
Vertical exhaust pipe fully enclosed system and cabinet-level solution
In addition, another solution is a cabinet-level cold and hot air isolation system. This system is usually an extension of the cabinet. The most common system is the cabinet vertical exhaust pipe system, or chimney cabinet system. The vertical exhaust duct system directs the hot return air from the enclosed cabinet to the ceiling. Compared with precise matching refrigeration, the chimney cabinet system has huge advantages. First of all, for a row of cabinets, the isolation of the hot and cold air system of the chimney cabinet is simpler and more effective than the exact matching refrigeration system to isolate the hot and cold air of the entire row of cabinets. Closed system. In addition, the chimney cabinet system is not connected to the air conditioning system, so that we can increase the cabinet arbitrarily as the demand increases, so that we have higher scalability. Finally, as shown in Table 1, the independence of the system and the air-conditioning system ensures that the data center can use a large air-conditioning system to improve cooling efficiency and save energy. Using the vertical exhaust pipe system, cold air can be supplied using raised floors (common air supply methods) or directly blowing cold air into the data center to supply air, and can be combined with air economizers to achieve better energy-saving effects.
The first challenge of the vertical exhaust pipe system cabinet is that we must use a ceiling or return air duct. In contrast, precise matching cooling does not require any ceiling or return duct. In this way, the data center needs additional height. The second challenge is the difference in wind pressure. We must ensure the wind pressure in front of and behind the cabinet so that cold wind can enter the cabinet to dissipate heat from the cabinet. This challenge is mainly reflected in the supply air pressure at the front of the cabinet, the air pressure at the back of the cabinet, the influence of the functional areas such as the cable management at the rear of the cabinet on the wind pressure, and the size and vertical exhaust pipe on the top of the cabinet. length. Therefore, we must be particularly careful in the design to ensure that the vertical exhaust pipe system does not cause erroneous pressure differences. But from the vast majority of cases, this passive cooling solution is currently the best solution.
Active chimney cabinets will only be used when the cabinet uses very long server equipment and the functional area at the rear of the cabinet is particularly tight. Active chimney cabinet refers to the addition of fans in the vertical exhaust duct. Active equipment adds a new layer of system structure, which directly affects the efficiency and complexity of the system. When it is not necessary, you should avoid installing active equipment.
In addition, there is a rack machine cooling scheme called backplane water cooling scheme, which is usually used in the rear door of the cabinet to cool the hot return air of the equipment, and report the cooled cold wind to the room. There is also a back-plate water cooling scheme with pipes at the rear of the cabinet, and the cooled cold air is sent into the front of the cabinet through the pipes to form an independent air circulation. The advantages of this solution are the same as the advantages of the exact matching cooling type cooling solution: the cooling system is very close to the server equipment being cooled, and the temperature of the room is suitable for the operating temperature of the operator. But it is precisely because of the existence of the cooling system at the rear of the cabinet that there is a tough problem: how to solve the difference in wind pressure and return air in the front and rear of the cabinet. In addition, we must also choose to face a series of problems such as the cost of using coolant such as cold water, investment cost, equipment failure and maintenance, and redundancy. These problems have been described in detail in the exact matching refrigeration refrigeration scheme. All three rack-level cooling solutions can increase the heat density of each cabinet by cooperating with the data center design and air conditioning system.
in conclusion
Both cold aisle sealing and hot aisle sealing (cold pool and hot pool) can improve the air flow organization of the data center, increase the heat density of each cabinet, and increase the temperature of the hot return air to improve the cooling efficiency of the air conditioning system. Just like the different characteristics of each scheme, the hot pool (HAC) has more scalability than the cold pool, the cooling efficiency and the comfort of working in the room, and the precise matching cooling is not limited by height and so on. If there is a ceiling or return air duct in the data center room, the vertical exhaust duct system has higher efficiency and redundancy performance in all solutions.
Marble Wood Cutting Board is regarded as a elegant decoration in modern kitchen. The marble part remains cool in room temperature, this low temperature marble surface makes it good for dough to keep firmed and need no constant flour powdering when you are creating delicious cakes or bread. The wood part keeps the board from rust and bacteria. A cutting or Chopping Board is a durable board on which to place material for cutting. The kitchen Cutting Board is commonly used in preparing food; other types exist for cutting raw materials such as leather or plastic.
Marble Cheese Board,Marble Cheese Kitchen Board,Marble And Wood Cheese Board,Marble And Wood Cutting Board
V-Boom's Industrial Co.Ltd , https://www.v-booms.com