Keeping Immersion Cooling Safe.

The Critical Role of Permittivity and Conductivity.

As artificial intelligence continues its rapid expansion, immersion cooling of servers is evolving just as quickly — from a niche solution into a serious alternative for high-performance data centers. In this approach, electronic components are directly submerged in specialized cooling liquids, known as immersion cooling fluids, which must be both thermally efficient and electrically safe. Two physical properties are particularly critical in this context: relative permittivity and specific electrical conductivity.

Relative permittivity describes how strongly a liquid dielectric influences an electric field and plays a crucial role in signal behavior and parasitic capacitances in immersion-cooled systems. Excessively high permittivity can promote unwanted coupling effects, while low polarizability may offer advantages in high-frequency applications.

At the same time, specific electrical conductivity is a direct measure of electrical safety. Ideally, immersion fluids are highly insulating to prevent short circuits in electronic components. In practice, however, these properties change over time—due to aging, contamination, or material leaching—and must therefore be continuously monitored.

With the growing industrial adoption of immersion cooling, the need for standardization is also increasing. The Open Compute Project (OCP) plays a key role in this development. Initial conventions and specifications define requirements for chemical stability, material compatibility, and, in particular, the electrical properties of cooling fluids. It becomes clear that electrical conductivity must not exceed certain thresholds in order to ensure operational safety. At the same time, recommendations for measurement methodologies and in-service monitoring are being established.

Although relative permittivity is less explicitly restricted than conductivity, it is gaining importance due to its influence on signal integrity, electromagnetic compatibility, and hardware design. OCP thus implicitly highlights the necessity of not only verifying initial fluid properties but also monitoring them during operation—an aspect that has often been underestimated.

Against this backdrop, precise measurement solutions are becoming increasingly important. In laboratory environments, flucon’s standardized system EPSILON+, compliant with DIN 51 111 and E DIN 51 113, enables detailed characterization of immersion fluids. It allows for the simultaneous determination of relative permittivity, specific electrical conductivity, and dielectric loss factor across a wide temperature range. This makes it possible not only to evaluate new fluids but also to investigate aging processes. This capability is particularly valuable for manufacturers and datacenter operators seeking to understand and optimize the long-term stability of their cooling media. Reproducible measurement data help identify trends and define threshold values that can later serve as references in field operation—bridging the gap between research, development, and practical application.

However, even more critical for real-world operation is continuous monitoring directly within the system.

This is where an inline-capable sensor such as our eps-inline comes into play. As a screw-in process monitor with a G3/4″ external thread, it can be integrated directly into the cooling circuit or even into the immersion tank itself, providing real-time data on the electrical properties of the fluid. This enables early detection of changes caused by contamination, moisture ingress, or material degradation.

For data center operators, this new technology represents a significant gain in operational reliability: instead of relying solely on periodic laboratory analyses, critical conditions can be identified immediately and appropriate countermeasures can be taken. At the same time, it opens up opportunities for condition-based maintenance and data-driven optimization of cooling processes.

In combination with OCP recommendations, this creates a holistic approach in which specification, measurement, and monitoring are closely aligned — allowing immersion cooling of servers, supported by flucon’s sensor technology, to take another step toward industrial maturity.

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