Guide to Water/Liquid Cooling

Discover more about water/liquid cooling in the Data Centre

Why liquid or water cooling in Data Centres is an alternative to the traditional Data Centre air conditioning system.

Utilising liquid or water cooling in Data Centres through the use of water-cooled racks, is fast becoming an alternative method to the traditional Data Centre air conditioning system of CRAC units. As servers have got smaller in size, server densities within 19” server racks have increased resulting in racks with higher heat loads, this increase in Data Centre cooling demand makes cooling the servers efficiently more of a challenge.

Whilst air-conditioned Data Centres can cope with lower density racks, they may struggle with racks with a higher processing and power density, often requiring additional cooling from in-row / in-rack air handlers. This is because air is a gas and as such has a poor heat conductivity. Whereas water has between 50 and 1,000 times the capacity to remove heat. There is a perceived serious downside to water cooling in that water and electronics do not mix well and the end result if they do could be catastrophic. However, the latest liquid / water cooled systems often use side or rear door heat exchangers that form their own self-contained system and offer leak protection to contain any leaks to the system itself; or in the case of some liquid cooling solutions use refrigerant liquids that turn to a gas if they leak. Data Centre liquid / water cooling is also more energy efficient. A Data Centre air conditioning system such as CRAC units uses more than 40kW of power to cool a 100kW data centre load. Compare this to a water-cooled system, such as the USystems ColdLogik system, for the same heat load it uses about 4kW.

What liquid / water cooled server rack options are there?

When it comes to liquid or water-cooled server racks there are several options available on the market. Most cabinet manufacturers will offer a liquid or water-cooled option.

EDP Europe offers a leading solution from ColdLogik.

ColdLogik is an advanced water-cooled server rack solution capable of cooling loads from 29kW up to 200kW per rack, depending on the type of Rear Door Cooler being utilised. The ColdLogik rear coolers are so effective that they allow the supply water temperatures to rise from the traditional 6°C for CRAC systems to between 14°C and 24°C, reducing chiller size and energy costs. ColdLogik rear door coolers have proven to be the ideal solution for Data Centre operators responsible for housing high density processing systems such as HPC clusters.

Available Rear Door Coolers include:

  • CL20 ProActive – provides up to 92kW of cooling,
  • CL21 Smart Passive – offers up to 29kW of sensible cooling.
  • CL21 ProActive – offers up to 30kW.
  • CL23 HPC ProActive – capable of providing cooling up to 200kW!

How does the ColdLogik water cooling system work?

At the centre of the ColdLogik water cooling system are the ColdLogik heat exchanger Rear Door Coolers, a range of passive and active RDCs that either come pre-installed to the rack or can be retro-fitted to existing racks via an interface frame or aisle cooler.

As the ColdLogik water cooling system can operate with higher water temperatures of between 14°C to 24°C the external cooling selection is less restrictive meaning that the rear coolers can be feed with water from other sources other than chillers, for example boreholes, rivers, lakes or sea water etc. Another benefit of the ColdLogik water cooling system is its optional patented Leak Prevention System (LPS) which, in the event of a pipework breach stops water from escaping. Not only that, but it allows the water cooling system to continue running unimpaired. The ColdLogik system works at its optimum energy performance when it is the sole cooling solution i.e. there is no additional air conditioning. All of the room’s cooling is provided by the Rear Coolers and managed by the ColdLogik Management System (CMS) and ColdLogik Room Management System (RMS) that constantly monitors the temperature and responds to the heat removal demands placed on the system to maintain the room’s ambient temperature.

Water Cooled Server Racks

How does the air heat exchange rear door affect server room cooling?

The ColdLogik Rear Cooler is a type of air heat exchange rear door, that controls the server room cooling process. Ambient air within the room is pulled into the cabinet and passes through the IT equipment. The resulting hot air produced by the IT equipment is exhausted directly on to the heat exchange rear door. Within the rear door is the water-cooled coil which removes the heat at source. The exiting air from the door provides the server room cooling and is returned into the room at a predetermined temperature. On active doors the fans are controlled by the CMS and will adjust in speed depending on the heat load so to maintain the ambient temperature.

Does a liquid cooled rack provide cooler server rack cooling?

A liquid cooled rack will provide greater server rack cooling than racks being cooled by traditional air conditioning. As previously mentioned air is a poor conductor of heat whilst liquid can dissipate much higher heat loads. As rack densities are increasing the need for better server rack cooling becomes more of a necessity.

In traditional Aisle Containment configurations there is the option of installing In Row Coolers that can either supply additional cooling or in slab environments provide the main cooling for a Cold Aisle Containment configuration.

More on Water/Liquid Cooling for Data Centres and IT Comms Rooms

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