Comparison of Air versus Liquid Cooling
Cooling playing a vital role in data centre operations and can account for 40% of operating costs. Liquid cooling offers an alternative technology to traditional air cooled systems, with both having their own advantages and disadvantages.
Air cooling has been the data centre industry standard for decades. It works by circulating chilled air through racks and server rooms, using fans, raised floors, and computer room air conditioners (CRACs) and computer room air handlers (CRAHs). In smaller computer and server rooms, split air conditiones are commonly used, again using a refridgerant to cool air which is then circulted. While relatively simple to install and maintain, air conditioners face growing limitations as servers become denser and power consumption increases. Air has a lower thermal conductivity than liquids, meaning that large volumes of energy are required to keep temperatures within safe limits.
In contrast, Liquid cooling, uses non-conductive fluids to absorb heat directly from components. Liquids transfer heat far more efficiently than air, making this approach ideal for high-density workloads such as artificial intelligence (AI) computers, cloud computing, and scientific simulations. Though installation costs are higher and the infrastructure more complex, liquid cooling allows for greater server rack densities, reduced energy consumption, and the potential to reuse waste heat.
The choice between the two depends on performance requirements, cost considerations, and sustainability goals. Wih rising compute demands, liquid cooling is seen as a more effective and future-ready solution for large-scale data centres.
| Feature |
Air Cooling |
Liquid Cooling |
| Heat transfer |
Less efficient |
Highly efficient |
| Energy consumption |
Higher (fans, CRAC units) |
Lower (better heat removal) |
| Rack density support |
Limited |
High-density workloads supported |
| Cost |
Lower upfront, higher operating cost |
Higher upfront, lower operating cost |
| Sustainability |
Less efficient, more waste heat |
Supports heat reuse, greener option |
Single and Two-Phase Immersion Cooling
With Single-Phase Liquid Cooling, the cooling liquid stays in the same phase throughout the cooling cycle. The liquid absorbs heat from the server components, warms up, and is then pumped to a heat exchanger where it releases the heat before being recirculated. The cooling liquid never boils or changes state; it just increases in temperature.
The advantges of a single-phase liquid cooling solution include simplicity in terms of its design, ease of miantenance and high reliability. The downside is that for very high heat loads, this liquid cooling approach is less efficient than two-phase liquid cooling systems.
With Two-Phase Liquid Cooling the cooling liquid undergoes a phase change (usually from liquid to vapor) when it absorbs heat from components. The vapor is then condensed back into liquid at a heat exchanger and recirculated. This approach uses the latent heat of vaporisation, which allows it to absorb much more heat at a nearly constant temperature.
The advantages of two-phase liquid cooling include a very high heat transfer efficiency, support for extreme power densities and lower energy usage from for pumping. The design is however more complex, has a higher capital cost and requires more careful management of fluid properties.
For more information on the liquid cooling solutions available from Server Room Environments please contact our Projects Team.
