Liquid Cooling : Analysis and Comparison of Three Liquid Cooling Technologies

With the explosive growth of data volume, a large amount of computing power needs to be supported by massive servers. Due to limited data center construction area and environmental regulations, increasing the power density of single cabinets has become a key solution to balance the growing demand for computing power and the limited carrying capacity of data centers. The massive data throughput and computation pose unprecedented challenges in energy consumption, heat dissipation, and noise reduction for data centers, which are emerging technologies such as artificial intelligence and big data.
In this context, liquid cooling data centers that apply liquid cooling technology and liquid cooling servers have emerged, providing new solutions for the cooling of data centers.

Liquid cooled server is a server system that uses liquid cooling technology to reduce server temperature. Traditional servers usually use air cooling for heat dissipation, while liquid cooled servers use liquid media to directly contact the heat dissipation components, effectively absorbing and eliminating the generated heat. Liquid cooled servers are divided into two types: direct cooling and indirect cooling. Currently, direct cooling is mainly immersed liquid cooling, while indirect cooling is mainly plate type liquid cooling

Analysis of Immersion Liquid Cooled Server:
Immersion liquid cooling is the process of immersing all heating components of IT equipment in a coolant to achieve heat dissipation. It can be divided into single-phase liquid cooling and phase change liquid cooling based on whether the working fluid undergoes phase change. Among them, coolant is the heat exchange medium for data centers, with high insulation, low viscosity, and strong compatibility characteristics, making it the main medium for immersion liquid cooling technology. The heat dissipation performance of the surface of heating devices such as motherboard chips greatly affects the heat transfer intensity of medium boiling. If the chip surface is smooth, the heat transfer coefficient of the liquid on the heat transfer surface is higher, thereby improving the rate of heat dissipation. The cooling liquid after heat absorption is cooled or condensed by circulating cooling or condensation methods such as air cooling or water cooling.
Analysis of Contact Liquid Cooling Server:
Spray type liquid cooling generally does not require significant changes to the infrastructure of data centers. It only relies on pump pressure or gravity drive to accurately spray cooling liquid onto IT equipment circuit boards from top to bottom according to heating element requirements. The heat absorbing cooling liquid is circulated and cooled through methods such as air cooling or water cooling. The spray type liquid cooling server is the main internal component of the entire spray system. With its high performance, low energy consumption, and highly reliable operation characteristics, it can effectively reduce the energy consumption of data centers.
Analysis of Cold Plate Liquid Cooling Server:
Cold plate liquid cooling is non-contact liquid cooling, and the cooling liquid does not directly contact the heating device. The cold plate liquid cooling system mainly consists of heat exchange cold plates, heat exchange units, circulation pipelines, cold sources, and other components. Cold plate liquid cooling transfers heat to the cooling liquid in the circulation pipeline, taking away the heat generated by the server through the refrigeration characteristics of the liquid itself, improving the cooling efficiency of the cold plate, significantly reducing energy consumption in the data center, and having strong noise reduction performance of the cold plate liquid cooling server. Cold plate materials are generally composed of materials with high thermal conductivity, making the surface of the cold plate close to isothermal, taking away a large amount of concentrated heat. The application of cold plates also reduces the pollution of cooling media on electronic components, improves the service life of data center facilities, and the noise of cold plate liquid cooled servers is much lower than that of air cooling, truly achieving a quiet data center.

Cold plate liquid cooling technology has strong application advantages in maintainability, space utilization, compatibility, and quiet noise reduction; However, in terms of cost, due to the separate customization of the cold plate device, the cost of technology application is relatively high. The spray type liquid cooling technology, on the other hand, significantly reduces the construction cost of data center infrastructure by transforming old servers and cabinets. Compared with the other two technologies, immersion technology has better performance in terms of space utilization and recyclability, although the maintainability and compatibility of the devices are poor, reducing energy consumption in data centers.

Market data comparison
At present, cold plate technology is mature and leading the commercial implementation. In the first half of 2023, cold plate accounted for 90% of the Chinese liquid cooled server market, mainly depending on the attention of traditional data centers to the cost and difficulty of original infrastructure renovation, as well as the high maturity of current cold plate solutions and good commercial foundation. Cold plate liquid cooling technology developed earlier, and currently, cold plate liquid cooling data center products have a relatively high market share. However, in the long run, the immersed type has significant advantages over the cold plate type in terms of heat dissipation efficiency, single cabinet power, space utilization, etc. Therefore, how to reasonably optimize infrastructure renovation and construction costs, as well as improve the application range and maintainability of electronic fluorinated liquids or other cooling liquids, has become a necessary condition for building a sustainable green data center.