Can compressor-assisted CDUs speed up liquid cooling adoption in existing data centres?

Liquid cooling is increasingly required for AI and high-performance computing workloads, yet most existing data centres lack the chilled-water infrastructure needed to support it. Compressor-assisted coolant distribution units (CA-CDUs) offer a potential retrofit pathway, enabling operators to introduce liquid cooling into air-cooled facilities without fundamental changes to existing cooling systems.  

Artificial intelligence and high-performance computing are changing the thermal profile of data centres. As rack densities increase, many operators are reaching the practical limits of conventional air-cooling approaches. This has accelerated plans to introduce liquid cooling into existing facilities.  

For new builds, this transition can often be incorporated into the original design. For existing buildings, it's more complex.  

Many live facilities were designed around direct or indirect air-cooling strategies and do not include chilled water infrastructure. Even where chilled-water systems exist, capacity is often fully allocated, and supply temperatures may be too high for liquid cooling applications such as direct-to-chip systems.

This raises a question for operators and hyperscalers: how can liquid-cooling capacity be introduced into an operational facility without fundamentally reconfiguring it?  

An emerging option we have researched is the compressor-assisted coolant distribution unit (CA-CDU), designed to support retrofit deployment.  

Introducing flexibility into liquid cooling

Traditional coolant distribution units (CDUs) act as the interface between liquid-cooled IT and wider facility cooling infrastructure. Typically, they provide hydraulic separation between the technical cooling systems serving IT racks and the facility water systems that ultimately reject heat from the building.  

Most CDU solutions currently assume access to chilled water. CA-CDUs remove the dependency on chilled water by integrating a refrigeration circuit directly within the unit.  

Alongside standard CDU components like pumps and heat exchangers, they use an onboard refrigeration circuit. Instead of relying on chilled-water infrastructure, heat is rejected via an external dry-air cooler connected to the unit’s condenser loop.  

This allows liquid cooling to be introduced in environments where chilled water either does not exist or cannot be practically expanded, making retrofit deployment more feasible.  

Matching cooling strategy to operating conditions

A key feature of CA-CDU technology is its ability to adapt its operation depending on ambient conditions.  

At lower outdoor temperatures, the system can operate in full free-cooling mode, transferring heat without using mechanical refrigeration, thereby reducing energy demand.  

As the outdoor temperature increases, the system transitions to mixed operation, combining free cooling with part-load compressor operation to maintain the target supply conditions.  

During warmer conditions, the unit can enter full mechanical cooling mode, in which the refrigeration capacity responds dynamically to cooling demand.  

This flexibility allows operators to maintain a stable technical water temperature while optimising energy performance across changing operating conditions.  

Turning product capability into deployable infrastructure

Technology alone does not determine whether deployment is successful.  

In a recent study with a hyperscale operator, we assessed how CA-CDU technology could be integrated into existing air-cooled facilities. The team also identified opportunities to strengthen the solution during product development, with retrofit deployment in mind.  

By considering not only the CDU but the wider impacts across operations and future scalability, the project demonstrated how introducing liquid cooling into existing environments requires a different approach, especially for retrofit deployment.  

As AI adoption continues to reshape infrastructure requirements, solutions that enable liquid cooling without extending chilled-water infrastructure are likely to play a critical role in retrofitting existing data centres for AI workloads. 

To learn more about adopting CA-CDU's into your existing data centre, speak to a member of our dedicated research and development team to find out more.