Why the CDU is the Unsung Hero of AI Data Center Acceleration

Just like a Formula 1 pit crew, Cooling Distribution Units don’t usually get a place on the podium but are critical to winning the AI infrastructure race.

At the recent Hungarian Grand Prix, Racing Bulls’ pit crew set a record for 2026 and changed four tyres on a Formula 1 car in 1.99 seconds — much faster than it took you to read this sentence.

But outside of die-hard fans, the pit crew won’t get much attention. The driver gets the trophy, the podium spray, the highlight reel. But perhaps shave even half a second off that stop and the driver might never make the podium at all.

The Cooling Distribution Unit (CDU) is effectively the data center liquid cooling’s pit crew. It rarely gets the spotlight — that’s reserved for the liquid cooled GPUs, the AI supercomputer, the latest LLM breakthrough.

A CDU is the hydraulic component that sits between a data center’s facility water supply and the cold plates embedded in liquid-cooled IT equipment, regulating coolant flow, pressure, and temperature to keep high-density AI servers operating reliably.

But those other innovations can only happen because something upstream is precisely metering, filtering, and pressurizing the coolant that keeps the entire system at its thermal optimum. Without the CDU, the “car” doesn’t even leave the garage, let alone get the chequered flag.

As a company that has spent decades engineering precision thermal management systems for mission-critical environments, Airsys is closely tracking this shift as liquid cooling moves from a niche solution to a foundational requirement for AI infrastructure.

“CDUs act as the hydraulic heart of many liquid cooling systems,” explains industry analyst Alex Cordovil from Dell’Oro. “Sitting between facility water and the cold plates embedded in IT systems, these units regulate flow, pressure, and temperature, while providing isolation, monitoring, and often redundancy.”

What Roles Does a CDU Perform in a Data Center?

The modern CDU fulfills at least three distinct yet connected roles in high-density data centers:

• The Regulator: CDUs control coolant flow to heat-generating IT equipment, maintaining optimal operating temperatures to ensure stable and reliable performance.
• The Mediator: CDUs bridge the gap between the data center’s cooling infrastructure and liquid-cooled servers, ensuring clean, thermally efficient, and protected heat exchange.
• The Strategist: Equipped with intelligent sensors and control systems, liquid cooling CDUs optimize energy use and cooling capacity, driving greater energy efficiency and seamless system operation.

But while CDUs aren’t exactly well known outside of hardcore data center circles, just like the intense rivalry in Formula 1, the innovation and competition in the CDU market is intensifying and attracting more attention and investment.

How Big Is the CDU Market?

Liquid cooling is mission-critical for modern AI data centers, according to Dell’Oro. The firm’s latest research puts thermal management as the fastest-growing segment of the Data Center Physical Infrastructure (DCPI) sector, with liquid cooling the fastest-growing technology “as rack densification moves the technology from an option to a precondition”.

As such it’s not surprising that competition to build and supply CDUs is also intensifying. The Data Center Direct Liquid Cooling (DLC) market could reach close to $6 billion by 2029, Dell’Oro states. The analyst firm has identified around 40 companies producing CDUs but believes there is room for “multiple vendors to thrive.”

Not all CDUs are created equal and there are a range of different CDU types from in-rack designs to liquid to air systems. The vendors that will prove most successful over time are those that understand that CDUs are an integral element of an entire system. “Successful vendors take a system-level approach, anticipating challenges across the deployment and leveraging the CDU as hardware tightly integrated with multiple elements to ensure seamless operation,” the analyst states.

Also, as with any product or service, it’s meeting the needs of the customer which is key to long-term success. A large portfolio of CDU products is useful in order to meet diverse customer needs but specialisation can also be key. “Breadth of portfolio helps hedge across deployment types, but it is not the only path to success. Vendors with a sharp edge in specific technologies can also capture meaningful share,” Cordovil explains.

What Makes CDU Commissioning Challenging?

Just like the focus on performance and safety in Formula 1, CDUs — like the rest of the liquid cooling thermal chain — also need to be tested and deployed in the right way. That means that processes such as commissioning become even more critical. Data center certification and services organisation Uptime Institute defines commissioning as a critical part of the design and build process: “The goal of commissioning is to prove a data center’s readiness to support the IT load at design capacity by demonstrating and documenting the performance of power and cooling systems,” Uptime explained in a recent research report.

According to Uptime, best practices for commissioning liquid-cooled data centers are still maturing, including commissioning of CDUs. “The commissioning of CDUs and the connected equipment in the technology cooling loop is not always straightforward for a range of reasons,” explains Uptime analyst Jacqueline Davis.

Part of that difficulty comes down to hydraulic balance — ensuring consistent coolant flow and pressure across every rack and cold plate in a loop, even as rack density and server configurations vary across a facility. Uneven hydraulic balance can leave some racks under-cooled while others receive more coolant than they need, undermining the reliability the CDU is meant to guarantee. Approach temperature — the difference between the coolant’s inlet temperature and the temperature it’s meant to bring components down to — is another key variable commissioning teams must validate, since a wider approach temperature signals less effective heat transfer at the cold plate.

Some issues, potentially related to the competition in the market identified by Dell’Oro, may be down to the fact that certain CDU suppliers simply lack data center experience. “Some of these companies had not sold any products to data centers before introducing their CDUs,” Uptime explains, and highlights the need for factory witness testing (FWT) — a pre-shipment verification process — to confirm that CDUs can withstand real-world operating conditions.

Why Does Manufacturing Footprint Matter for CDU Deployment?

As with the F1 pit team at the Hungarian Grand Prix, the CDU obviously has a critical role to play and deserves more adulation than it receives — hopefully that will change over time. And Formula 1 teams aren’t the only ones pushing technical boundaries in the central European country. Airsys — which specialises in liquid cooling including CDUs — recently opened its European manufacturing facility close to the country’s capital Budapest. The facility adds to a growing global footprint including a new US HQ in South Carolina.

As Dell’Oro analyst Alex Cordovil noted at the time, the Hungarian facility will enable one of the core drivers for CDU success — meeting specific customer needs. “A global manufacturing footprint is increasingly a prerequisite for serving data center customers at scale,” he said. “Airsys’ European facility strengthens its ability to support complex air and liquid cooling deployments as infrastructure designs become more bespoke and timelines continue to compress.”

The new European facility adds to a growing global footprint including a new US HQ in South Carolina. The site in Woodruff serves as the company’s global hub for high-efficiency, zero-water cooling technologies supporting the rapid growth of AI and edge infrastructure. By localizing production and engineering in South Carolina, Airsys is positioning operations closer to its North American customers while strengthening control over its global manufacturing processes

What’s Next for CDU Technology?

But just as pit crews may eventually get replaced by dextrous robots, and perhaps drivers by AI, innovation is likely to continue in the liquid cooling space with potential advancement beyond current CDU designs — for example much larger Facility Distribution Units (FDUs), which serve multiple racks or rows rather than a single rack. However for now, the CDU remains a critical, if somewhat unsung hero, of the AI era.

Check out FluidCool-X for more on Airsys CDUs. With integrated features delivering rated thermal efficiency and an ultra-low PUE below 1.05, a 4°C (7.2°F) Approach Temperature that surpasses industry standards, and triple-layer redundancy delivering 99.999% uptime, FluidCool-X embodies the precision and resilience required in modern facilities.

Related Reading

While direct-to-chip and immersion are leading alternatives for high-density racks, 80% of data hall square footage still requires precision air control — which is where modular CRAH and edge air platforms like Airsys’ Optima2™ fill the gap.

📖 Read our deep dive: Just Like Hybrid Powertrains, Air Cooling Remains Essential to High-Density AI Infrastructure

In Part 2 of this series, we’ll take a closer look at how Airsys’ CDU engineering stands apart from newer market entrants — and why that distinction matters for operators evaluating long-term reliability.

FAQ

What does a CDU do in a data center?

A CDU regulates coolant flow, pressure, and temperature between a facility’s water supply and the cold plates in liquid-cooled IT equipment, enabling stable operation of high-density AI servers.

Why is the CDU market growing so quickly?

Rising AI compute density is driving demand for liquid cooling. Dell’Oro projects the Direct Liquid Cooling market could reach close to $6 billion by 2029, with around 40 companies now producing CDUs.

What is hydraulic balance in a CDU system, and why does it matter?

Hydraulic balance refers to consistent coolant flow and pressure across every rack and cold plate in a cooling loop. Poor hydraulic balance can leave some racks under-cooled, undermining system reliability.