Liquid Cooling
Liquid cooling is a data center cooling method that uses liquid coolants (often water) to absorb heat from computing equipment. This method can appear in several ways.
One type of liquid cooling, illustrated above, is called evaporative cooling, and uses cooling towers to draw hot air through water-saturated media, with the water's evaporation absorbing heat from the air. The cooling tower is used to cool the chiller's condenser water, allowing the chiller to circulate colder water to the computer room, where it is either supplied to the CRAH or circulated directly through the IT racks.
condenser water from the chiller's
Evaporative cooling works by using the natural principle of water evaporation to absorb heat and cool the air. Hot air is drawn through water-saturated media, where the water's evaporation absorbs heat from the air, thus lowering its temperature before it circulates through the data center to cool the servers. There are two main types: direct evaporative cooling (DEC), which cools the air directly by passing it through water-soaked pads, and indirect evaporative cooling (IEC), which uses a heat exchanger to transfer the cooling effect to a separate air stream without directly contacting the data center air.
fans and air conditioning units (often within the computer room in the form of CRAHs) to circulate cool air between IT racks, expelling the hot air from computing equipment.
Air-liquid hybrid cooling in data centers uses both air and liquid methods to manage heat, with liquid cooling handling high-heat components and air cooling managing less demanding areas or components. Liquid cooling uses cold plates on processors or immersion tanks to directly transfer heat to a coolant, which is then circulated to a chiller or dry cooler. The liquid is then cooled and recirculated, while air cooling, via units like CRAHs or rear-door heat exchangers, handles the broader server environment and smaller components. This combination provides efficient, flexible thermal management for high-density servers, optimizing energy and water usage.
Considered the most traditional cooling method, air cooling is used by approximately 80% of data centers. It is most suitable for smaller data centers, because it is sufficient for smaller heat loads while being cost-effective and easy to implement on a small scale. However, for larger data centers with a more significant heat load, air cooling is insufficient and must be supplemented or hybridized with other methods like liquid cooling.
In cooler climates, some data centers can reduce energy consumption by circulating ambient cool air to cool equipment (known as free cooling), bypassing the energy-intensive process of conditioning the air.
On average, air-cooled data centers have a relatively inefficient power usage effectiveness of 1.70, but a near-zero water usage since they do not directly use water for cooling, not considering their associated indirect water use.