# Liquid Cooling

[![liquid cooling.png](https://hydraulogistics.at/uploads/images/gallery/2025-09/scaled-1680-/liquid-cooling.png)](https://hydraulogistics.at/uploads/images/gallery/2025-09/scaled-1680-/liquid-cooling.png)

<span style="white-space: pre-wrap;">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 a variety of ways. </span>

<span style="white-space: pre-wrap;">One type of liquid cooling, illustrated above, is called </span>[evaporative cooling](https://hydraulogistics.at/link/16#bkmrk-evaporative-cooling)<span style="white-space: pre-wrap;">, and uses </span>[cooling towers](https://hydraulogistics.at/link/16#bkmrk-cooling-tower)<span style="white-space: pre-wrap;"> 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 </span>[chiller](https://hydraulogistics.at/link/16#bkmrk-chiller)<span style="white-space: pre-wrap;">'s condenser water, allowing the chiller to circulate colder water to the computer room, where it is either circulated directly through the IT racks or, in a hybridized system using </span>[air cooling](https://hydraulogistics.at/books/chilled-infrastructures/page/air-cooling "Air Cooling")<span style="white-space: pre-wrap;">, supplied to the </span>[CRAH](https://hydraulogistics.at/link/16#bkmrk-crah)<span style="white-space: pre-wrap;">. Another variant of liquid cooling is </span>[immersion cooling](https://hydraulogistics.at/books/chilled-infrastructures/page/immersion-cooling "Immersion Cooling")<span style="white-space: pre-wrap;">, in which servers and IT equipment are directly submerged in a </span>[dielectric fluid](https://hydraulogistics.at/link/16#bkmrk-dielectric-fluid)<span style="white-space: pre-wrap;"> coolant to remove heat. </span>

<span style="white-space: pre-wrap;">In terms of liquid supply, liquid cooling can use either a </span>[closed-loop](https://hydraulogistics.at/link/16#bkmrk-closed-loop-system)<span style="white-space: pre-wrap;"> or an </span>[open-loop](https://hydraulogistics.at/link/16#bkmrk-open-loop-system)<span style="white-space: pre-wrap;"> system. Closed-loop systems are more expensive to implement, but recirculate the coolant to reduce water use and prevent contamination. Open-loop systems are more cost-effective, but use water only once before disposing of are more water-intensive and involve a higher risk of environmental contamination. </span>

Liquid cooling (excluding the immersion cooling variant) is used by about 16% of data centers. Compared to air cooling, liquid cooling is more energy-efficient and is equipped to handle larger, higher-density servers.

<span style="white-space: pre-wrap;">On average, liquid-cooled data centers (excluding immersion cooling) have a </span>[power usage effectiveness](https://hydraulogistics.at/link/16#bkmrk-pue)<span style="white-space: pre-wrap;"> of </span>[1.38](https://hydraulogistics.at/books/chilled-infrastructures/page/comparing-impacts-by-cooling-type "Comparing Impacts by Cooling Type")<span style="white-space: pre-wrap;">, and a relatively inefficient </span>[water usage effectiveness](https://hydraulogistics.at/link/16#bkmrk-wue)<span style="white-space: pre-wrap;"> of </span>[1.90](https://hydraulogistics.at/books/chilled-infrastructures/page/comparing-impacts-by-cooling-type "Comparing Impacts by Cooling Type")<span style="white-space: pre-wrap;">, not considering their </span>[indirect water use](https://hydraulogistics.at/link/16#bkmrk-indirect-water-use).

<span style="white-space: pre-wrap;">Depending on their location, some data centers can take advantage of existing water features to reduce energy consumption. For example, in </span>[Marseille, France](https://hydraulogistics.at/books/chilled-infrastructures/page/marseille-france "Marseille, France")<span style="white-space: pre-wrap;">, Interxion uses a form of liquid-based </span>[free cooling](https://hydraulogistics.at/books/chilled-infrastructures/page/free-cooling "Free Cooling")<span style="white-space: pre-wrap;">, sourcing water from a tunnel that carries flowing water at a natural, consistent temperature of 15C. Although the water still requires some filtration, the facilities bypass the need for extensive cooling processes, improving its </span>[power usage effectiveness](https://hydraulogistics.at/link/16#bkmrk-pue)<span style="white-space: pre-wrap;"> to </span>[1.11](https://hydraulogistics.at/books/chilled-infrastructures/page/comparing-impacts-by-cooling-type "Comparing Impacts by Cooling Type").