immersion liquid cooling application in data cennter
With the rapid development of computing intensive applications such as artificial intelligence, Internet of things, cryptocurrency and AR / VR, the increasing computing demand makes the data center gradually develop to "high performance, high density and high energy consumption". The energy consumption of the data center is roughly composed of communication and network equipment, power supply and distribution system, lighting and auxiliary equipment and cooling system, Among them, the energy consumption of the cooling part accounts for about 40% of the total energy consumption of the data center. Improving the efficiency of the cooling system of the data center and reducing energy consumption are very important to achieve the goal of "double carbon".
Common liquid cooling methods include cold plate, spray and immersion. Among them, immersion liquid cooling has the highest heat transfer efficiency and can avoid local hot spots. It is the most likely technical means to solve various problems faced by the cooling system in the high-performance computing environment.
Higher energy efficiency:
Immersion liquid cooling uses coolant as the heat transmission medium. The liquid has higher thermal conductivity and specific heat capacity, so it can conduct heat faster and absorb heat more effectively. At the same time, because the use of fans and air conditioners is reduced, the data center using immersion liquid cooling technology has lower pue.
Higher power density:
In addition, it can effectively prevent the equipment from being immersed in the air and humidity due to the poor temperature of the cooling liquid, which can effectively protect the equipment from the corrosion of the cooling liquid and the fan in the machine room.
Higher space utilization:
The excellent thermal performance of immersion liquid cooling enables the servers to be closely arranged without separation distance, and there is no need to configure fans. There is no need for air conditioning and refrigeration units in the machine room, no need to install closed facilities for cold and hot channels, and no need for raised floors. Therefore, immersion liquid cooling has higher space utilization than traditional cooling solutions.
Realization of immersion liquid cooling:
The heat generated by immersion cooling liquid can be divided into two phases: Single phase liquid immersion cooling and two-phase liquid immersion cooling .
Single phase liquid immersion cooling:
In the single-phase immersion liquid cooling system, all heating components of IT equipment are completely immersed in the circulating non-conductive coolant, and the heat emitted by the equipment is directly transmitted to the coolant. The coolant of single-phase immersion liquid cooling usually has a high boiling point, and the coolant will not change phase after absorbing heat, and will always remain in the liquid state.
Two-phase liquid immersion cooling :
When the cooling liquid is immersed in the condenser, a large amount of heat will be absorbed into the boiling liquid, and will be absorbed by the liquid cooling liquid. At the same time, a large amount of heat will be absorbed by the liquid cooling liquid which is immersed in the condenser to the boiling point, The heated cooling water in the condenser is discharged through the circulating cooling liquid system.
Problems and challenges：
1. Although the submerged liquid cooling technology has excellent heat dissipation performance, there is not a strong demand for conventional data centers to upgrade the traditional heat dissipation scheme to submerged liquid cooling except for specific scenarios such as encrypted digital currency mining.
2. Because the submerged liquid cooling technology uses liquid heat dissipation, in order to be compatible with the coolant, the hardware equipment usually needs to be properly adjusted to adapt to the submerged cooling. Although some OEMs have supported the equipment suitable for the submerged liquid cooling, many equipment manufacturers have not designed or tested the submerged liquid cooling.
3. When calculating the deployment cost of the submerged liquid cooling system, it is necessary to comprehensively consider all the actual expenses. It includes not only the price of the liquid cooling equipment tank and coolant and the subsequent maintenance cost, but also the transformation and maintenance cost of a series of other facilities such as pumps, heat exchangers, filters and sensors to meet the design practice of the liquid cooling system.
