A Guide To Liquid Cooling For High-Density Equipment Racks

March 18, 2024

Technology is constantly improving, and so does the amount of data it produces. As applications become more data-intensive, they need more support from computing resources. High-density racks increase the computing power you can yield in a smaller space, which is becoming increasingly essential for accommodating our growing computing requirements.

However, safely installing this equipment is a challenge for many data centers. Implementing high-density racks requires special considerations for cooling — more specifically, it requires data centers to consider advanced liquid cooling techniques.

High-Density Racks Are the Future of Data Centers

A high-density server contains more CPUs than a standard server. Though they have more computing resources, high-density servers take up roughly the same amount of space as ordinary IT equipment, which allows data centers to do more with less space.

Resource-intensive applications like artificial intelligence and virtualization draw significantly more energy than conventional uses, generating more heat. Data centers now produce more heat than ever, as low-density racks are also beginning to require more power than in previous generations.

High-density servers will likely become increasingly common as digital transformation initiatives continue ramping up over the next few years. Conventional air cooling systems will become less suitable for handling such high-heat loads, so many experts advise data centers to proactively embrace liquid cooling.

The demand for liquid cooling will follow suit as our computing needs continue increasing.

Benefits of Liquid Cooling for High-Density Racks

Liquid cooling is the optimal choice for high-density IT equipment for several reasons.

  • Noise levels: Liquid cooling eliminates the need for noisy fans, which can help keep sound levels within the ranges specified by the Occupational Safety and Health Administration.
  • Efficiency: Because liquid is an incredibly effective medium for capturing and transferring heat, liquid cooling systems can cool high-density racks with less energy and fewer emissions than comparable air cooling systems.
  • Cost savings: Because liquid cooling has such low energy requirements — even for high-density racks — it costs less over time than standard air cooling systems.
  • Sustainability: Liquid cooling’s efficiency also makes it better for the environment, allowing you to shrink your data center’s carbon footprint dramatically.
  • Small footprint: Liquid cooling systems don’t require a large computer room air conditioning unit or bulky air ducts, allowing you to maximize your floor space.

You can also use multiple types of cooling within your data center to keep costs low. For example, you might use air cooling systems for low-density equipment and liquid cooling for high-density racks.

Best Types of Liquid Cooling for High-Density Server Racks

Here are the three most common types of liquid cooling systems used for high-density equipment racks.

1. Liquid-to-the-Rack Cooling

A liquid-to-the-rack cooling system places coils containing chilled water in the rear of the cabinet. These coils connect to the chilled water loop that runs through the facility, absorbing heat and transporting it out of the cabinet.

This technique improves upon the standard computer room air handler system by eliminating the need for hot air to travel to the perimeter. Instead, hot air can exit through the back of the cabinet as it cools, allowing it to cycle to the front more quickly.

2. Direct-to-Chip Cooling

Also known as direct liquid cooling, this technique involves taking coolant directly to the source by attaching cold plates to heat-generating chips like CPUs and GPUs.

These cold plates connect to coolant-filled tubes that extract the heat from the chips and transport it to one of two destinations:

  • An external heat exchanger
  • Outside the system

The direct contact between the cold plate and the chip allows for highly efficient heat transfer, which is how this technique can support incredibly high heat loads of 100 degrees Fahrenheit or above.

Unlike immersion cooling systems, the server and the liquid never come into contact in direct-to-chip configurations. The coolant only touches the cold plate connected to the chip.

3. Immersion Cooling

Immersion cooling is the most advanced and effective cooling technique available for high-density servers. It involves submerging the servers in a thermally conductive dielectric cooling liquid, usually either a mineral oil or a specialized fluid.

This liquid has a higher specific heat capacity than air, which means it absorbs and moves more heat than an air cooling system. Direct contact with the server allows it to absorb the maximum amount of heat possible before quickly transferring it out of the cabinet.

This technique can use two different configurations.

  • Single-phase: The hot coolant gets pumped to an external heat exchanger via a coolant distribution unit, where the heat gets transferred out of the liquid and into the facility water supply. The now-cool liquid circulates back into the bottom of the immersion chamber, and the cycle begins again.
  • Double-phase: This passive system submerges the equipment in a dielectric fluid with a low boiling point. The liquid boils when the device generates heat, which floats up to the top of the chamber as vapor. Through convection, the vaporized fluid cools, condenses and sinks back to the bottom of the chamber.

Both configurations are highly energy-efficient and can rapidly cool high-density equipment, even under extreme temperatures. However, double-phase cooling is slightly more sustainable due to the lack of active cooling equipment.

How to Choose the Correct Cooling System

These are the three most critical considerations for installing a cooling system in a data center with high-density equipment.

  1. Current thermal needs: How much cooling does your existing equipment require? Does your current system meet those needs?
  2. Future growth: Will you require a higher cooling capacity if you add more racks or switch to high-density servers? How much?
  3. Efficiency: What is the most energy-efficient system you can choose to meet your facility’s needs? How can you optimize for sustainability?

For the best results, partner with a data center expert with a proven track record of successful deployments. A reliable data center provider can help you design, install and maintain an efficient cooling system that meets your goals.

Contact DataSpan for Advanced Data Center Cooling Solutions

Our experts can help if you’re considering installing modern liquid cooling for IT equipment racks. DataSpan has 50 years of experience designing custom data center solutions for facilities of all sizes and configurations, so you can count on us to create a solution that optimizes performance and meets company specifications.

Learn how the DataSpan team can work with you to prepare your facility for the future of computing. Contact us today for more information about our data center cooling services.