Thermal Density: The X Factor of Liquid Cooling Science cover

Thermal Density: The X Factor of Liquid Cooling Science

On: August 16, 2023 Comments: 0
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Data centers need to cool their servers for safety and performance. A key factor determining the proficiency of your cooling system—and, therefore, your data center’s IT capacity—is thermal density. This is a measure of the amount of heat within a given unit of volume.

Consider systems like high-performance computing (HPC) facilities. Each cubic foot or meter contains a lot of hot equipment. The same goes for other systems with high thermal density, such as large data centers or racks full of the latest graphics processing units.

The thermal density of IT equipment influences which cooling solution you can use. As data center temperatures rise globally, the increase in thermal density is forcing the industry to adopt better cooling technology. More specifically, liquid cooling technology. The amount of heat produced by a system is proportional to the amount of cooling it needs, and liquid immersion cooling gives you far more bang for your buck.

Liquid immersion cooling has an extremely high capacity to transfer heat relative to air cooling, making it the right tool for the job when it comes to handling newer and more powerful chips. Air cooling infrastructure simply can’t manage the heat produced by the latest servers which run processor-intensive AI and similar tasks.

As chip technology evolves, along with higher thermal density and the ensuing power demands, data center and rack density are increasingly under pressure. Even newer approaches like rear-door heat exchangers (RDHx) don’t accomplish enough. The only practical solution is true liquid immersion cooling.

Why Thermal Density Matters for Data Center Cooling

thermal density
Source: Shutterstock

Thermal density is one of the main limiting factors in terms of data center productivity. As such, it’s critical to have enough cooling capacity for the processors, and enough processors for the end-user applications.

To illustrate, thermal density controls the cooling load and the cooling capacity of a system. And that cooling load represents the quantity of heat you have to take out of a system to keep the temperature in balance. This load is also influenced by other variables. For instance, the server room temperature, heat transfer rate, and physical surface area of components.

In essence, your IT equipment produces a certain amount of heat, and the cooling system’s job is to remove that heat quickly and affordably. For today’s hot processors with their extremely high thermal density, liquid immersion provides a practical and cost-effective solution.

The Science of Thermal Density for Data Centers

If you want to calculate the cooling load, the relevant formula is:

Q = U A (T1– T2)

In this equation, “Q” stands for the cooling load, measured in watts. “U” is for the total heat transfer coefficient, measured in watts per square meter degree Kelvin. “A” represents the surface area in square meters, and “T” is temperature in degrees Kelvin. “T1” is the system temperature, while “T2” is the server room temperature.

There are many related properties one can calculate. For example, “sensible heat” is a measure that applies to perceptible changes in temperature. In contrast, “latent heat” describes heat exchange, which, instead of changing the temperature, alters traits like the phase of matter. The sum of these two measures is known as the “total heat.”

Although these are general concepts that apply to heating and cooling, they also outline the constraints under which data centers operate.

Driven by a demand for machine learning and other functions dependent on processor capability, each generation of data center hardware features more chips per server at a higher power per chip. As chip technology advances and thermal density continues to grow, innovative cooling solutions like liquid immersion will become ever more crucial.

Image showing thermal density.
Source: Shutterstock

How Liquid Cooling Can Help Manage Thermal Density

Liquid cooling responds to the challenge of high thermal density by offering a more efficient method of removing heat. High-density systems require the faster cooling that liquid immersion provides over conventional air cooling. This explains why supercomputers and other high-density systems have been early adopters of liquid cooling.

Now that mainstream chips are becoming more powerful and emitting more heat, the transition to efficient and affordable liquid cooling is in full swing. Data centers of all sizes can benefit from liquid immersion cooling systems, like Green Revolution Cooling’s (GRC’s) market-leading solutions. In addition, the technology is environmentally friendly, so the switch to green cooling comes at just the right time.

Liquid immersion cooling helps data centers reduce their power and water use, carbon footprint, capital expenses, and operational costs. It’s a substantial improvement over air cooling, mainly because liquid transfers heat over a thousand times more effectively than air. Liquid is simply more efficient; and in critical situations, you can’t afford to waste time.

How to Optimize Data Center Liquid Immersion Cooling for Thermal Density

In addition to choosing efficient liquid immersion cooling over inadequate air cooling, there are several other approaches to managing high thermal density. To start with, look at the various liquid coolants on the market. Examine their properties, such as thermal conductivity, viscosity, and specific heat. Each of these elements influences performance. There are currently several coolants available for data center needs. A liquid immersion cooling expert like GRC can guide you through the options.

The design and configuration of the cooling system also affect its cooling capacity. Relevant factors include flow rate, pressure, and temperature. Then, you have the location and orientation of the heat sources and heat sinks such as chips, piping, tanks, and more. Again, the professionals can steer you toward the best choices. Many of these optimization gains result from the configuration of the liquid cooling systems themselves.

Finally, one can monitor and control the cooling system for performance. GRC System Manager brings reporting data, including operating temperatures and pressures, to a single interface. It issues alerts if any anomalies are found, which you can customize and receive by email or text message. It’s also possible to examine detailed logs and connect securely to the vendor for immediate support.

Manage High Thermal Density with GRC’s Liquid Cooling

The heat’s rising fast in data centers, along with the continued growth of processor- and heat-intensive applications. Greater thermal density is becoming too hot to handle with traditional air cooling. That’s why data centers are turning to GRC’s high-capacity liquid immersion cooling systems.

Liquid’s unparalleled ability to remove server heat (up to three orders of magnitude better than your last air-cooling system) solves the thermal density problem. Now, and for the long term, liquid immersion cooling overcomes the physical limits that prevent air cooling from advancing any further.

Make your next data center cooling solution resilient to the demands of high thermal density. Contact GRC, the innovator of powerful liquid immersion cooling for next-gen systems.