Immersion Cooling for Data Centres: How It Works
Data centre power densities continue to rise, and traditional air cooling is reaching its practical limits. High-performance computing (HPC), artificial intelligence (AI) and machine learning generate concentrated heat loads that challenge conventional thermal designs.
As rack heat loads increase, the industry faces a practical question: What is the future of data centre cooling - immersion cooling or direct-to-chip liquid cooling?
This article explains what immersion cooling is, how it works in data centres, and whether it is worth adopting compared with other liquid cooling approaches.
What Is Immersion Cooling?
A liquid-based cooling method that submerges IT equipment in a thermally conductive liquid. Instead of removing heat using chilled air, the liquid absorbs heat directly from electronic components.
How Immersion Cooling Differs from Air Cooling
Air-cooled data centres rely on airflow, raised floors, fans and containment to move heat away from servers. Liquid based cooling systems remove the air path entirely.
Key differences include:
- No server fans or airflow management
- Direct heat transfer from components to liquid
- Higher achievable rack power densities
Why Liquid Is More Effective Than Air for Heat Removal
Liquids have a much higher heat capacity and thermal conductivity than air. This allows liquid based cooling systems to remove heat more efficiently with less energy input, particularly at high densities.
How Immersion Cooling Works
At a basic level, immersion cooling replaces air with liquid as the heat transfer medium inside the IT environment.
The Role of Dielectric Fluids
Immersion systems use dielectric fluids that do not conduct electricity. These fluids are engineered to:
- Safely contact live electronics
- Remain chemically stable over time
- Transfer heat efficiently
Heat Transfer and Thermal Management Explained
Heat generated by processors and other components moves directly into the surrounding liquid. The system then transports this heat away using pumps, heat exchangers or secondary cooling loops connected to facility infrastructure.
Types of Immersion Cooling Systems
Data centres use several liquid immersion system designs, each with different operating principles and performance characteristics.
Single-Phase Immersion Cooling
In single-phase systems, the dielectric fluid remains in a liquid state. The warmed fluid circulates through a heat exchanger and returns to the tank once cooled.
Two-Phase Immersion Cooling
Two-phase systems use fluids that boil at low temperatures. When components heat the fluid, it vaporises. The vapour then condenses on a cooled surface and returns as liquid.
Key Differences Between Single-Phase and Two-Phase Systems
- Single-phase systems are mechanically simpler
- Two-phase systems can offer high heat transfer efficiency
- Fluid cost, handling and maintenance differ significantly
Why Immersion Cooling Is Gaining Traction in Data Centres
Growing rack densities and more demanding workloads are pushing data centres to look beyond traditional air-based cooling methods.
Although immersion cooling receives strong industry attention, it is not yet a mainstream data centre solution. Adoption remains concentrated in specialised AI and high-performance computing environments, particularly in purpose-built facilities.
Supporting High-Density and High-Performance Computing
Immersion cooling supports rack densities far beyond typical air-cooled limits. This makes it suitable for environments where space, power and performance must align.
Meeting the Cooling Demands of AI and Machine Learning Workloads
AI workloads often produce sustained, high thermal output. Immersion cooling provides consistent temperature control, which supports performance stability and reduces heat-related performance slowdowns.
Key Benefits of Immersion Cooling
Liquid immersion systems offer measurable benefits across energy use, infrastructure design and hardware performance.
Improved Energy Efficiency and Lower PUE
By reducing reliance on mechanical cooling and fans, immersion cooling can significantly lower cooling energy consumption.
Reduced Cooling Infrastructure and Fan Power
Without airflow management, data centres can reduce:
- Fan energy
- Air handling units
- Complex containment systems
Increased Hardware Reliability and Lifespan
Stable operating temperatures and the removal of airborne contaminants can improve component reliability.
Lower Noise and Reduced Airflow Requirements
Immersion environments operate quietly and without high-velocity airflow.
Challenges and Considerations of Immersion Cooling
Liquid-based cooling introduces operational, design and maintenance considerations that data centre operators must assess carefully.
Infrastructure and Facility Design Implications
Immersion systems require changes to:
- Rack design
- Floor loading
- Cooling distribution architecture
These changes reshape both the physical layout of the data hall and how cooling systems connect to IT equipment.
Maintenance, Servicing and Operational Change
Technicians must adapt to new servicing processes, including fluid handling and specialised procedures. These changes often require additional training, updated safety procedures and adjustments to standard maintenance workflows.
Compatibility, Standards and Vendor Lock-In
Not all hardware is immersion-ready, and fluid compatibility varies by vendor. Standardisation is still evolving. These factors can limit hardware choice, affect long-term flexibility and increase dependence on specific suppliers.
Immersion Cooling vs Other Liquid Cooling Approaches
Data centres can choose from several liquid cooling approaches, each with different levels of complexity, performance and operational impact.
Immersion Cooling vs Direct-to-Chip Liquid Cooling
As rack densities increase, most data centre operators compare immersion cooling with direct-to-chip liquid cooling.
Direct-to-chip systems remove heat from processors and GPUs using cold plates while air continues to cool secondary components. Immersion cooling submerges the server and removes airflow from the system entirely.
Direct-to-chip cooling currently sees broader adoption because it integrates more easily into existing rack designs and facility infrastructure.
When Immersion Cooling Makes Sense - and When It Doesn’t
Immersion cooling is most effective for:
- AI and HPC workloads
- Extremely high rack densities
- Purpose-built or specialised environments
It may be less suitable for mixed-use or legacy facilities.
For many facilities, direct-to-chip liquid cooling provides a more flexible and incremental upgrade path. It allows operators to increase rack density without fully redesigning the data hall or introducing large-scale structural changes.
The Role of Immersion Cooling in Sustainable Data Centres
Cooling systems play a central role in improving the environmental performance of modern data centres.
Reducing Energy and Water Consumption
Certain liquid cooling approaches, including immersion systems, can reduce water use and support higher operating temperatures , aligning with sustainability goals. This approach can lower reliance on water-intensive cooling methods and improve overall energy efficiency.
Waste Heat Reuse and Sustainability Opportunities
Captured heat can be reused for facility heating or exported to external systems, depending on design. This creates opportunities to improve overall energy efficiency.
How Immersion Cooling Fits into Modern Data Centre Cooling Strategies
Modern data centres often combine multiple cooling methods to balance performance, efficiency and operational flexibility.
Hybrid Cooling Environments and Transitional Designs
Most modern data centres now deploy hybrid cooling environments that may include:
The Importance of Holistic Cooling Architecture
Effective cooling strategies consider workload type, density, scalability and operating impact, not just thermal performance. This broader view helps data centres align cooling design with long-term capacity planning, energy efficiency and operational resilience.
Key Takeaways: Is Immersion Cooling Right for Your Data Centre?
Immersion cooling delivers strong thermal performance in ultra-high-density environments. However, it is not yet a universal or mainstream solution.
As rack heat loads continue to grow, the future of data centre cooling will likely involve multiple liquid technologies, including direct-to-chip systems and targeted immersion deployments.
The most effective strategy aligns cooling technology with workload density, facility constraints and long-term scalability goals.
Explore data centre cooling strategies that balance performance, efficiency and long-term resilience. Contact Stulz.
FAQs
1. What is immersion cooling in a data centre?
Immersion cooling is a liquid cooling method where servers and IT hardware are submerged in a non-conductive dielectric fluid. The liquid absorbs heat directly from the components and transfers it away through heat exchangers or cooling loops.
2. Why is immersion cooling used in high-density data centres?
Immersion cooling can manage much higher heat loads than traditional air cooling. This makes it particularly suitable for high-performance computing, AI and machine learning environments where rack power densities are significantly higher.
3. What is the difference between single-phase and two-phase immersion cooling?
Single-phase immersion cooling keeps the fluid in a liquid state and circulates it through a heat exchanger. Two-phase systems use fluids that boil at low temperatures, allowing heat to be removed through evaporation and condensation cycles.
4. How does immersion cooling compare with direct-to-chip liquid cooling?
Direct-to-chip cooling removes heat from processors using cold plates while the rest of the server is still cooled by air. Immersion cooling submerges the entire server in liquid, eliminating airflow and allowing higher thermal performance.
5. What are the main benefits of immersion cooling for data centres?
Immersion cooling can reduce cooling energy consumption, support higher rack densities, remove the need for server fans and maintain more stable operating temperatures for IT equipment.
6. Is immersion cooling suitable for all data centres?
Not necessarily. Immersion cooling is most effective in specialised environments with extremely high computing densities. Many facilities adopt direct-to-chip liquid cooling instead because it integrates more easily with existing infrastructure.