A water-cooled server rack is designed to allow for water to transfer heat from the servers. Compared to traditional air-cooling methods, water-cooled server racks consume less floor space and less power.
How Do Water-Cooled Server Racks Work?
The server racks are surrounded by pipes in which water flows through to a water block attached to the processing units. There, the heat transfer occurs, and the warmed water is sent to a radiator. At the radiator, fans remove the heat from the pipes by blowing cool air over them so that the process can repeat. There may be reservoir present to hold extra water to provide more thermal mass and water capacity. Also, an anti-fouling solution may be added to the water to prevent bacteria or algae.
There are two types of water-cooling systems that can be used to cool the server racks: open loop and closed loop. An open loop system is designed by the user and is built from individual components. However, a closed loop system, also called all-in-on (AIO) is a preassembled unit that can be purchased and installed. The optimal system depends on the needs and characteristics of the data center as open loop systems allow for more design flexibility while closed looped systems are simpler and more reliable.
What are the Advantages and Disadvantages of a Water-Cooled Server Rack?
Although water cooling is more efficient than air cooling as water conducts heat about 30 times better than air, it can be dangerous to use water near electrical equipment. Since water is an electrical conductor, it can damage equipment if there is contact. Therefore, server racks in facilities that prioritize uptime and ease of maintenance often do not use water cooling. Water cooling requires additional maintenance such as water level monitoring and the replacement of aging components.
However, there are still some significant benefits provided by water cooling, including a greater cooling capacity, the ability to cool higher density components, less noise, and increased energy efficiency.
What are the Types of Server Rack Water Cooling?
Water cooling can take a few different forms depending on the needs of the facility and the organization of the racks. These methods include:
- Evaporative cooling. During evaporative cooling, a large fan draws warm air through pads saturated with water. As the water in the pads evaporates, the air is chilled and pushed out of the room. Temperature is controlled by adjusting the airflow of the cooler. Evaporative coolers are rated by the volume of warm/cool air that can be exchanged in one minute as well as the amount of energy they require to run.
- Rear-door water cooling. Cooling units are connected to the water mainline and ambient air is pulled into the cabinet via active equipment fans. Hot exhaust air is passed over a heat exchanger matrix and is then transferred and rejected. Chilled air is created from this process and is passed back into the room at the same temperature as the ambient air.
- Waterborne data centers. The facility is built on a barge and is cooled from recirculated water from the ocean or other large body of water. This process is an open-loop system where the water travels through a multi-step filtration process and is then brought into the heat plate exchanger. The water is used to cool water from a closed loop system and is returned to its source once the process is complete.
How is Efficiency Measured with a Water Cooled Server Rack System?
While water cooling can be a very efficient method of data center cooling, it is important to ensure the most efficient usage of the water, especially since data centers already use an average of 3-5 million gallons of water per day. Water Usage Effectiveness (WUE) is a metric that measures data center sustainability in terms of water usage and its relation to energy consumption. It is the ratio between water usage in a data center and the energy consumption of the IT equipment, and the goal is to get the WUE as low as possible.
WUE = Data Center Water Consumption (in liters) / IT Equipment Energy (in kilowatt hours)
The average data center has a WUE of 1.8L per 1kWh, and this number is projected to decrease as data centers aim to be greener and reduce their carbon footprint.
DCIM Software and Water-Cooled Server Racks
Data Center Infrastructure Management (DCIM) software collects, reports, and alerts on data from power and environmental sensors to ensure that the data center is being cooled efficiently.
Key aspects of DCIM software that contribute to a more efficient cooling system include:
- Measuring and monitoring data center energy consumption for more intelligent management decisions for the facility
- Environment monitoring to better understand the current conditions and determine what areas need improvement
- Tracking power, environment, energy, and cost data in real-time to monitor the impact of data center energy efficiency initiatives on KPIs
- Data center automation capabilities, zero-configuration charts and reports, and visual analytics that aid in reducing energy consumption
Want to see how Sunbird’s world-leading DCIM solution can help you efficiently cool your data center? Get your free test drive now!