As summer temperatures soar into the high thirties and low forties, how do devices cope with constant exposure to heat when people seek refuge in air-conditioned rooms?

With AI computing power growing exponentially towards high performance, density, and energy consumption, AI servers are nearing the limits of air cooling efficiency. Liquid cooling, known for its superior efficiency and lower energy consumption, is emerging as the preferred solution for high-density computing environments.

Advantages of Liquid Cooling

1. Rapid Heat Dissipation: Liquids, with their high thermal conductivity and specific heat capacity, can absorb over 3000 times more heat per unit volume compared to air, making liquid cooling significantly more efficient than air cooling.

2. Energy Efficiency: Aligned with national carbon neutrality goals, the Power Usage Effectiveness (PUE) index is a critical measure of equipment efficiency. Liquid cooling systems, with fewer power-intensive components like compressors and fans, mainly using water pumps and sensors, can drastically reduce PUE.

3. Enhanced Space Utilization: For instance, immersion cooling can significantly increase server density per unit space in data centers, supporting high-density computing more effectively.

Mainstream Liquid Cooling Technologies

• Cold Plate Liquid Cooling: Uses cold plates to directly cool high-power devices such as CPUs and GPUs, alongside air cooling for other components.

• Spray Cooling: Stores liquid at the top of the chassis and sprays it onto heat-emitting components, akin to a shower, for effective device cooling.

• Immersion Cooling: Fully submerges heat-emitting devices in coolant liquid, similar to taking a bath in cool water. This can be classified into single-phase and two-phase immersion cooling based on whether phase change occurs during the cooling cycle.

Currently, cold plate liquid cooling dominates the market with over 90% share due to lower costs, mature technology, and compatibility with existing operational habits. However, immersion cooling offers superior heat dissipation efficiency in the long term, especially as server power consumption increases. Future advancements may see immersion cooling as the ultimate solution.

Limitations of Liquid Cooling

Challenges include unstable technologies, such as phase transition issues in cold plate systems, which can lead to flow instability and deteriorated heat transfer efficiency. High costs also hinder widespread adoption, encompassing equipment costs like tanks and coolant, as well as maintenance costs for pumps, heat exchangers, filters, and sensors.

The maturity of the industry chain remains another obstacle. The close coupling of cooling and heating sources requires system integrators to possess both cooling and heating source handling capabilities and understand ICT architecture. Current barriers upstream and downstream in the industry chain have yet to be fully addressed.

Despite higher initial costs compared to traditional air cooling, as technology iterates and equipment costs decrease, the tipping point in liquid cooling's total cost of ownership (TCO) advantage may soon be reached. This could pave the way for a significant surge in the liquid cooling market.