Computer room air conditioning (CRAC) is vital to keeping IT equipment functioning properly. The right data center cooling solution literally keeps your business up and running.
The heat that IT equipment itself generates, along with the heat and humidity of the environment, can cause CPUs, hard drives, and other components to slow down or shut down entirely if overheating occurs. That can mean lost productivity, lost data, and even damage to the equipment.
IT managers are technology experts, but not necessarily HVAC experts. So let’s take a look at some cooling methods and best practices to protect your servers and other vital IT systems.
A quick look at data center cooling methods
There are a number of different approaches designed to move heat from a closed environment — the data center — to the outside. A simple portable cooling unit may be enough for equipment closets or small server rooms. But an engineered cooling solution may ultimately be more efficient and cost-effective for a data center.
Air cooling methods
Most air cooling systems take advantage of the fact that warm air rises. Traditionally, these systems use room-based units arranged in one of a number of configurations, depending on whether you want to cool an entire room, rows of equipment, or a specific rack or cabinet.
As the name says, whole-room cooling systems position AC units to maintain an even temperature throughout a room. However, since warm and cool air can easily mix, having a negative effect on efficiency, this type of data center cooling uses one of various design options to isolate warm air from cooler air. For instance:
- Raised floor — Here, cool air is supplied from underneath an elevated, perforated floor. The cool air is drawn up into the equipment, where it picks up waste heat and releases it as warm air. That warm rises and is collected, cooled, and returned to beneath the floor to repeat the process.
- Hot aisles and cold aisles — In this data center cooling design, IT equipment is positioned so that its air inlets face a “cold aisle,” where cooled air is delivered by a cooling unit and sucked into the equipment. The hot exhaust from the back of the equipment is released and returned to the cooling unit intakes via “hot aisles.” This helps to ensure good separation between the supply (cool) and return (hot) air paths.
Air cooling units can also be positioned to focus on rows of cabinets or specific equipment racks. This also allows you to direct cold air to the equipment with the most stringent requirements for temperature control. The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) provides guidelines for allowable temperatures in data centers, depending on the type of electronic equipment.
Liquid cooling methods
Liquid-based methods allow cooling to be focused where it’s needed instead of trying to maintain a temperature throughout an entire room. So, for instance, a liquid cooling system can be designed to deliver chilled water directly to a server rack or cabinet.
Liquid cooling utilizes chillers to remove heat to the outside. These systems often use a cooling tower to provide cool water or refrigerant, which is transported directly to the equipment racks/cabinets or to a computer room air handler (CRAH) in the data center.
While these systems can be very efficient, using a liquid for data center cooling also has drawbacks. There is the risk of leaks, which could damage valuable IT equipment, and the use of a chilled liquid can cause condensation. Liquid cooling systems also are more complex and require additional infrastructure for containing and transporting the liquid. That makes liquid cooling more expensive than air cooling systems.
“Free” cooling methods
Supplementing air- or liquid-based cooling methods are so-called free methods. These typically use outside air and evaporation to transfer heat while cutting back on the cost of running chillers and compressors. For data centers where ASHRAE’s guidelines allow for operation at higher temperatures, some use of free cooling may be an option.
Best practices for data center cooling
The efficiency of data center cooling is all about where the cooling units are placed and, for the predominant air cooling systems, how the air is distributed. Below are some best practices for these systems, based on ASHRAE recommendations:
- When deciding on the airflow architecture, consider all the options — overhead, in-floor, in-row, and hybrid solutions.
- Use computational fluid dynamics (CFD) modeling to analyze the configurations and make sure the one you choose will optimize the airflow in your data center.
- Make sure the data center cooling method you choose will provide good separation between the air supply and return paths. This can be accomplished through the use of a design strategy such as hot and cold aisles.
- Opt for energy efficient fans, fan motors, and variable frequency drives (VFDs) to optimize the overall efficiency of your data center cooling solution.
- Don’t over-cool your IT systems. Instead, be more energy efficient by opting for the highest feasible supply air temperature as recommended by ASHRAE.
- Think ahead and choose a solution that is modular or scalable. That way, your data center cooling infrastructure will be able to support higher server density and increased loads due to growth.
How expert advice can help you keep your cool
Clearly, data center cooling system design is a complex task, and there is a lot riding on getting the right solution in place. For any data center professional who is not an HVAC specialist, the best practices and all the choices can be daunting.
The air conditioning experts at Arista can help you implement the best data center cooling solution for your needs, whatever they may be:
- Designing a new computer room, floor, or data center from the ground up
- Replacing an existing cooling solution to improve IT reliability and uptime
- Reconfiguring your current data center cooling solution to support growth
In addition, a well-maintained data center cooling system is more energy efficient and reduces the risk of equipment failure, to keep your cooling and IT systems up and running. Here, too, Arista can help, with a customized HVAC maintenance plan that will keep your data center cooling solution in peak condition.
To learn more about data center cooling options for your business, download our free advisory publication: The Ultimate Guide to NYC Light Commercial Air Conditioning.
