Transitioning to Immersion Cooling: Ensure Success with High Performance Infrastructure

Liquid cooling is no longer niche. In fact, it’s becoming the status quo for hyperscalers and AI data centers. A recent report from Del’Oro Group positions single-phase direct liquid cooling as “the prevailing architecture for most deployments through the end of the decade,” while also forecasting a projected rapid growth of the liquid cooling market to almost $7 billion in manufacturer revenue by 2029. This is no surprise: as rack densities increase and power consumption continues to threaten operational efficiency, liquid cooling offers a scalable, high-performance solution. The up-front costs of installing a liquid cooling system are quickly offset, as energy expenditures are cut by as much as 40%.

When transitioning to a liquid cooling method for their data centers, hyperscalers and AI data center operators may trend towards immersion cooling for its superior heat transfer capabilities. Immersion cooling systems may also advance organizations’ sustainability goals, reducing energy expenditures and conserving more water than other liquid cooling methods. However, there are a variety of considerations that data center operators must take into account when transitioning to an immersion cooling system to get the best return from their investment; and while some of them are surely on your radar, there’s one small but vital aspect that often gets overlooked.

Namely, the cabling.

Implementing Sustainable, High-Performance Immersion Cooling

When most think of the tradeoffs associated with changing from one type of cooling technology to another, they don’t think about cabling. Instead, they’re mostly thinking about the most intensive changes associated with adopting immersion cooling systems: server performance, power usage, plumbing connections, facility modifications, etc.

However, if you’re transitioning from an air-cooled system, your cabling might not necessarily be well-suited for submersion in thermically-conductive fluids. Using sub-optimal cabling in an immersion cooling environment can negatively impact the performance and efficiency of your system in a variety of ways – from constantly replacing cables as jackets stiffen to pollution of the dielectric fluid.

Dielectric Fluid, Signal Integrity, and Implications for System Performance

Notably, different methods of immersion cooling (single-phase or two-phase cooling, respectively) utilize fluids with distinct chemical compositions, each with their own implications for cooling and signal loss. Single-phase cooling fluids are typically hydrocarbon-based mineral oils which have a high boiling point, high viscosity, and low toxicity. Two-phase cooling fluids are fluorine-based, with lower boiling points, low viscosity, and a high purity – however, these fluids tend to evaporate quickly, which can require more frequent replacements. Mileage will also vary depending on which family of fluorinated fluids is used: hydrofluoroethers, for example, have good thermal conductivity, but not the strongest dielectric properties, limiting the number of applications it can be utilized for.

According to research presented within the Open Compute Project (OCP), signal loss from both fluids averages out at <0.02 from 10 MHz to 40 GHz. However, this research also depicts variance in signal loss with different combinations of fluids and connectors, revealing a crucial truth – that loss is impacted by the fluid used, the cabling involved, and how the two interact with each other.

Inefficient cabling and incompatible materials can negatively affect the efficiency of the system as a whole. However, the trick is that while there are a couple of materials and components we can solidly identify as problematic in immersed systems, what actually performs well within different systems may vary. This is largely due to the variety of fluids and materials that may be utilized within different systems and how they interact with one another – which is why testing your cabling at and above OCP compatibility requirements is so crucial.

Cable Materials: Exploring Compatibility with Immersion

As mentioned before, not all cable materials are designed for long-term immersion. PVC sheathing is one of the clearest examples of this. In theory, PVC-sheathed cabling works in the short-term, as the outer casing does allow the cable to work as intended while immersed. However, in the long-term, PVC sheathing stiffens and erodes, leaching some component materials into the immersion fluid and acting as a significant source of contamination. While data center operators might be tempted to utilize PVC-sheathed cable, as it has a lower price tag that may facilitate a rapid transition, they will ultimately spend much more on replacement cabling and fluid maintenance.

It’s almost always a good idea to check with the fluid provider and the cable manufacturer to see whether their products are actually compatible long-term. As interactions can vary significantly depending on cable material, fluid composition, and cooling method, any manufacturer worth their salt will have tested their products extensively, and can define when and how their product operates ideally.

This is why Leviton Network Solutions recently launched its TORRENT™ cabling designation; to give data center operators insight into which cabling systems will perform well in immersion cooling systems. Products with the TORRENT designation are tested per OCP Materials Compatibility in Immersion Cooling Rev 1.0, ensuring reliable performance in dielectric fluid environments. Plus jacket and insulation materials for TORRENT-designated products are put through additional tests beyond OCP compatibility requirements to ensure consistent performance. As our list of compatible fluid-providers continues to grow, we’re confident that we’re bringing you a solution that will ensure a sustainable, high-performing immersion cooling system, and the best return on your infrastructure investment to date.