Immersion Cooling Technology: The Future of Data Center Heat Management

As rack power consumption soars to unprecedented levels, the data center industry is undergoing a massive transformation. Driven by compute-intensive Artificial Intelligence (AI) and High-Performance Computing (HPC) applications, data centers have rapidly transitioned from using air cooling strategies for racks dissipating 10-20 kilowatts to now requiring cooling systems capable of handling 120-kilowatt racks powered by NVIDIA's Grace Blackwell superchips—just for the cooling needs of a single server cabinet!

Traditional air cooling technology is no longer sufficient to address such high heat dissipation demands, paving the way for the development of advanced liquid cooling solutions. The current mainstream liquid cooling options are primarily divided into two categories: "direct-to-chip" and "immersion" cooling. Unlike traditional air cooling methods, these technologies use liquid mediums such as water or insulating fluids to dissipate heat from the equipment.

This article explores immersion cooling technology, analyzing its working principles, advantages, challenges, and its potential applications in high-power environments.

Immersion Cooling Technology: Fully Submerged Components

Immersion cooling technology completely submerges servers and other electronic components in an insulating liquid. As the equipment generates heat during operation, this heat is transferred to the surrounding cooling medium. The heated liquid rises to the surface, is directed to the cooling system to dissipate the heat, and then returns to the initial liquid reservoir housing the equipment.

There are two types of immersion cooling:

1. Single-Phase Immersion Cooling

This system fully submerges all servers and IT equipment in an insulating liquid. When the temperature of components such as CPUs or GPUs increases, the fluid absorbs the heat generated. The heated fluid is then pumped to a heat exchange unit where it is cooled, and the cooled fluid is returned to the equipment’s liquid reservoir. 

Advantages:

●Complete heat absorption: All heat generated by servers (GPU, CPU, memory modules, etc.) is collected and dissipated by the cooling system.

●Insulating liquid: Ensures that the components remain protected from short circuits.

Challenges:

●Thermal Design Power (TDP) limitations: When the GPU’s TDP exceeds 700 watts, single-phase immersion may struggle to provide effective cooling.

●Infrastructure investment: Significant investments are required for the redesign of data center infrastructure, including large, heavy liquid reservoirs. This makes it better suited for new data centers or existing facilities that can accommodate large-scale renovations and structural reinforcements.

●Compatibility with insulating liquids: All components (servers, connectors, printed circuit boards, etc.) must be compatible with the insulating liquid to prevent damage. This often requires custom equipment or modifications to the servers.

●Mechanical redesigns: Some server components, like fiber optic connectors, do not function properly in an immersion environment and need mechanical modifications.

●Fire hazard: The fluids used in immersion cooling, often hydrocarbon-based, are flammable and pose significant risks if a fire occurs in the data center.

●Maintenance difficulties: Any maintenance work requires cranes to remove servers from the liquid reservoir, followed by a 30-minute waiting period for the fluid to drain before repairs can begin.

●Contamination issues: If the cooling fluid becomes contaminated (e.g., water), the reservoir needs to be drained and cleaned, which could result in downtime for up to a day.

2. Two-Phase Immersion Cooling

Similar to single-phase immersion, this system submerges the servers and IT equipment in an insulating liquid. However, when the components heat up, the fluid begins to boil and generate steam. This steam rises to the top of the liquid reservoir, where a cooling water pipe network is installed. The steam condenses upon contact with the cooling pipes, turning back into liquid and dripping back into the reservoir. Meanwhile, the heated water in the cooling pipes carries the heat away from the equipment and out of the data center. 

Advantages:

●Complete heat absorption: Like single-phase immersion, this system fully absorbs all heat from servers (GPU, CPU, memory modules, etc.) for efficient cooling.

●Supports high TDPs: Two-phase immersion cooling can handle much higher heat loads compared to single-phase systems.

●Insulating liquid: Prevents short circuits, ensuring safe operation of the equipment.

Challenges:

●Compatibility with insulating liquids: Similar to single-phase immersion, all components must be compatible with the insulating liquid to avoid damage, requiring specialized equipment or server modifications.

●Cavitation damage: The boiling process in two-phase systems can cause cavitation, which may damage IT components, printed circuit boards, and solder joints.

●Infrastructure investment: Like single-phase systems, two-phase immersion cooling demands heavy investment in infrastructure, including large reservoirs and reinforced building structures to accommodate the additional weight.

●Maintenance challenges: Due to the weight of the reservoirs and immersion devices, maintenance work typically requires cranes, leading to prolonged downtime.

●Environmental impact: Each time the liquid reservoir is opened for maintenance, perfluoroalkyl substances (PFAS) vapors are released into the atmosphere. This results in about a 10% annual loss of the cooling fluid (hundreds of liters), contributing to environmental concerns.

Conclusion: The Future of Data Center Cooling

Immersion cooling technology, with its ability to handle extremely high heat loads efficiently, is fast becoming a key solution for modern data centers, particularly those designed to support AI, HPC, and other intensive applications. While there are clear benefits to these systems in terms of heat management and energy efficiency, the significant infrastructure requirements, potential for environmental impact, and maintenance challenges should be carefully considered.

As the demand for high-performance computing continues to grow, immersion cooling systems are poised to play a critical role in ensuring that data centers can scale effectively while managing their increasing power consumption and heat dissipation needs.

At Tongyu Technology, we are a leading provider of thermal solutions. Feel free to reach out to us for customized cooling solutions tailored to your data center's needs.