Data Center Liquid Cooling Technologies: DTC, RDHx and Immersion

As AI and high-performance computing push rack densities higher, liquid cooling has moved from an emerging technology to an important part of data center infrastructure planning.

But “liquid cooling” is not a single technology.

Direct-to-chip cooling, rear door heat exchangers and immersion cooling each address heat differently and have different implications for the data center environment. Understanding those differences is important when evaluating how to support higher-density infrastructure.

Why Liquid Cooling?

Traditional air cooling remains effective for many enterprise environments. The challenge emerges as compute density increases.

AI servers and GPU clusters generate significantly more heat than traditional enterprise infrastructure. As rack densities increase, moving enough air through the environment becomes increasingly difficult and inefficient.

Liquid has significantly greater heat-transfer capacity than air, allowing heat to be captured closer to the source and removed more efficiently.

For high-density environments, this can provide several advantages:

• Support for higher rack densities
• Improved thermal efficiency
• Reduced dependence on server fans
• Greater flexibility in data center space utilization
• More consistent thermal performance for high-density compute

The question for data center operators is increasingly not whether liquid cooling will play a role, but which approach is appropriate for the environment.

Three Approaches to Data Center Liquid Cooling

Direct-to-Chip Liquid Cooling

Direct-to-chip, or DTC, cooling uses cold plates mounted directly to high-heat components such as CPUs and GPUs.

Coolant circulates through the cold plates, absorbs heat from the components and transfers that heat through the liquid cooling infrastructure.

DTC has become particularly important for high-density AI infrastructure because it removes heat directly from the components generating it while allowing other server components to continue using air cooling.

A DTC environment may include:

• Cold plates
• Server manifolds
• Rack manifolds
• Coolant distribution units
• Facility water connections
• Supply and return piping
• Leak detection and monitoring
• Controls and commissioning systems

This creates an important distinction. DTC is not simply a different way of cooling a server. It introduces a new physical infrastructure layer that must be integrated with the IT environment.

For large AI deployments, that integration must also happen repeatedly and consistently across potentially hundreds of racks.

Rear Door Heat Exchangers

Rear door heat exchangers, or RDHx, use a liquid-cooled heat exchanger mounted at the rear of the rack.

Instead of bringing liquid directly to individual processors, the system captures heat from the hot exhaust air as it leaves the servers.

RDHx can be particularly useful for organizations that need to support higher rack densities while retaining more of their existing air-cooled IT infrastructure.

Potential advantages include:

• Increased cooling capacity within an existing footprint
• Reduced hot aisle temperatures
• Support for higher-density racks
• Less modification to IT equipment than DTC
• Flexibility for hybrid air and liquid cooling environments

RDHx can provide an effective bridge between traditional air cooling and more extensive liquid cooling architectures.

However, implementation still requires careful consideration of water distribution, rack configuration, floor loading, airflow, maintenance access and facility infrastructure.

Immersion Cooling

Immersion cooling takes a fundamentally different approach.

Servers or components are submerged in a dielectric fluid that absorbs heat directly from the equipment. The heat is then transferred from the fluid to the facility cooling system.

Because immersion eliminates much of the traditional air-cooling infrastructure around the server, it can support very high compute densities and provide excellent heat-transfer efficiency.

However, immersion also changes how equipment is installed, serviced and operated.

Considerations can include:

• Specialized tanks or enclosures
• Hardware compatibility
• Different maintenance procedures
• Fluid handling
• Facility layout changes
• Equipment access
• Operational training

For these reasons, immersion tends to be considered for specialized environments where its density and efficiency advantages justify the larger operational change.

DTC vs. RDHx vs. Immersion

There is no single liquid cooling architecture that is right for every data center.

Direct-to-chip cooling is increasingly relevant for high-density AI and GPU infrastructure where heat needs to be removed directly from high-power components.

Rear door heat exchangers can provide a practical way to increase cooling capacity while retaining conventional air-cooled server infrastructure.

Immersion cooling can support extremely high-density environments but requires more substantial changes to equipment, operations and data center design.

The right approach depends on more than rack density. Facility infrastructure, workload requirements, existing equipment, deployment schedules, scalability and operational requirements all need to be considered.

For a deeper look at when liquid cooling makes sense and what successful deployment requires, read our guide to Data Center Liquid Cooling: When and How to Deploy for AI Infrastructure at Scale.

The Infrastructure Behind Liquid Cooling

Regardless of the technology selected, successful liquid cooling requires coordination between facility infrastructure and IT infrastructure.

That becomes especially important with direct-to-chip cooling.

CDUs, manifolds, piping, cold plates, racks, servers, power, networking and monitoring systems must ultimately function as one integrated environment. Installation sequencing, connection procedures, testing, documentation and commissioning all become part of the deployment.

And as AI infrastructure scales, so does the execution challenge.

A liquid-cooled environment with a handful of racks presents a very different deployment challenge from an AI environment with hundreds of racks, thousands of GPUs and compressed deployment schedules.

This is where experience in physical infrastructure execution matters.

From Cooling Technology to Operational Infrastructure

Liquid cooling technology continues to evolve, but the larger shift is already underway.

Higher-density compute is changing how data centers are designed, deployed and operated. Direct-to-chip cooling, RDHx and immersion each provide different ways to address those requirements.

Choosing the technology is only one part of the equation.

The next challenge is turning that technology into operational infrastructure.

Silverback Data Center Solutions supports the physical deployment and integration of high-density data center and AI infrastructure, including direct-to-chip liquid cooling environments. Our teams bring the operational discipline of enterprise data center services to the speed and scale required for next-generation infrastructure.

If you have questions about Liquid Cooling or other Data Center Solutions such as migration, relocation, deployment, staffing, auditing or decommissioning, please reach out to Silverback Data Center Solutions at info@teamsilverback.com.