Hyperscale data centers are contending with an unprecedented surge in heat output, driven by powerful AI chips and increasingly dense workloads. Liquid cooling has been an effective thermal management solution for multiple generations of computing. Still, the step-change shift from legacy enterprise workloads to high-density GPU deployment has increased the performance stakes while raising critical questions.

 

At Mikros Technologies, we often get asked: What are the best coolants for data center liquid cooling systems? 

The short answer: It depends on your application. Whether you're using water, glycol, dielectric fluids, or new formulations just entering the market, the properties of the coolant will directly impact system performance, cost, and long-term reliability.

Here's what you need to know:

Coolant 101: Why Fluid Selection Matters

The job of a coolant is simple — carry heat away from sensitive electronics. But the performance of that task hinges on multiple physical properties:

• Specific heat capacity – how much heat the fluid can absorb per unit of mass

• Thermal conductivity – how efficiently it moves heat within the fluid

• Viscosity – how easily it flows through tight microchannels and plumbing

• Electrical conductivity – whether it poses a risk in the event of a leak

• Freezing/boiling point – which affects performance and maintenance windows

When designing high-efficiency cold plates and thermal loops, Mikros Technologies’ engineers tailor the heat exchanger geometry to the coolant’s behavior. Every element — channel width, manifold design, flow rate — depends on understanding and optimizing these variables.

Water: The Gold Standard for Heat Transfer

From a thermodynamics perspective, water is the best coolant you can use. It has a high specific heat capacity, excellent thermal conductivity, and low viscosity, which makes it highly efficient at absorbing and transporting heat — even in tight enclosures and dense chip packaging.

When systems permit it, Mikros Technologies recommends using water for cold plate cooling loops. It's cost-effective, readily available, and has well-known performance characteristics. But there’s a catch: pure water doesn’t play well with metals. Corrosion, scaling, biological growth, and freezing risks require that water systems be carefully conditioned with additives and maintained under strict monitoring and controls.

Glycol Mixtures: Water Plus Practicality

To address the real-world challenges of using water, many customers deploy aqueous glycol mixtures, such as:

• Ethylene glycol (EG)

• Propylene glycol (PG)

These are typically mixed with water in concentrations ranging from 20% to 70%, depending on the temperature requirements, and also have algaecide and corrosion inhibitors. Glycol protects against freezing, making it particularly valuable in colder climates, outdoor enclosures, or for freeze-protection during shipping.

However, the tradeoff is performance. Glycol has a lower specific heat, lower thermal conductivity, and a higher viscosity than pure water, which means coolant loops must be adjusted through larger flow channels, require more pumping power, or have an increased surface area in the heat exchanger. Mikros Technologies accounts for these design changes by optimizing cold plate geometry for the specific glycol blend used in your system.

Dielectric Fluids: Safe but Less Efficient

For sensitive electronics environments, non-conductive coolants are preferred; this is where dielectric fluids come in. Dielectrics are mainly used in semiconductor test environments, where equipment is in constant motion and leaks or spills are more common. The main types of dielectric coolants include:

• Fluorinated fluids

• Synthetic hydrocarbons

• Silicone-based oils

Dielectric coolants offer peace of mind: They won’t short out a board if there’s a leak. They're ideal for both single-phase and two-phase immersion systems, as well as for cooling power electronics, RF components, or telecom infrastructure. However, they come with tradeoffs:

• Lower thermal conductivity than water

• Lower specific heat

• Higher cost

• Environmental and disposal considerations (for some formulations)

Mikros Technologies’ cold plates can be customized to accommodate these fluids, with flow patterns and internal geometries that minimize pressure drop and maximize heat dissipation, even in single-phase dielectric cooling loops.

Emerging Coolants: What's Next?

The data center industry is also exploring next-gen coolant formulations designed specifically for increased performance, reliability, and efficiency. Some promising directions include:

• Bio-based coolants that reduce environmental impact

• Refrigerants in two-phase loops

As new coolants enter the market, Mikros Technology partners closely with OEMs, integrators, and hyperscale operators to test compatibility and optimize cold plate performance accordingly. The goal is to provide designers with more thermal budget headroom, freeing them to increase power density without compromising performance or longevity.