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Liquid Cooling for Electronics Enclosures

Monday, March 17, 2014 by Stäubli Connectors

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The heat being generated by high power electronics is outstripping the cooling capability of air, promoting a move towards more powerful techniques. Leading in this development is the use of liquids to transfer heat directly from electronic components inside enclosures to external heat exchangers. Stäubli, a specialist in connection technology, manufactures connectors that ensure the critical enclosure cooling circuit connections are totally leak free, robust and reliable.

Faster processing speeds, increased capacity and higher power density in electronics produce more heat, higher junction temperatures and increased risk of failure. Traditionally, air-cooling has been the solution, using a combination of heat sinks, heat pipes and fans to remove the heat produced from the enclosure. High power electronics now being used in many real-time processing applications are rapidly outstripping the capability of any air-based cooling system.

Liquids have a much higher cooling capability than air; water is 24 times more conductive than air and is approximately 100 times more efficient at removing heat. Liquids are therefore ideal for use in transferring the heat being generated away from the electronic components and enclosure and into a heat exchanger where the liquid can be efficiently cooled and recycled back into the enclosure cooling system.

Placing liquids in close proximity to sensitive electronics is a major concern. Any leakage in the enclosure would be disastrous - how could leaks be avoided?

This is where Stäubli's experience and expertise in connectors provides the solution. The company's range of connectors has been specifically designed to meet these demanding requirements; its unique coupling design ensures fast, secure and reliable circuit connection and disconnection. Flat faced, clean break connector technology guarantees no spillage and eliminates any risk of air or contaminants entering the circuits.

"We needed connections that could be guaranteed to be leak free and still easy to use, only Stäubli were able to meet these requirements."

Stäubli's connectors can also be designed for blind connection that can compensate for a large degree of mis-alignment; this ensures that connection to the liquid cooling circuit does not compromise the integrity of the electrical connectors; removal and replacement of liquid cooled enclosures can be as easy as on a traditional air cooled system.

Liquid cooled electronics are now being used across a broad range of applications, from radar arrays and imaging systems in the defence sector to power converters in wind turbines. Many data centres are evaluating this new technology and the benefits it offers in terms of reduced power consumption or increased processing capacity.

A recent application illustrates the benefits of liquid cooling. Thermacore Europe, based in Ashington, Northumberland, is a specialist in thermal management technology, especially for cooling electronics. When designing its latest system using liquid coolant, rather than air, the company called on the experience and expertise of Stäubli to provide the easy to use and reliable spill free, automatic connectors required.

The new system can remove up to 500W of heat energy from a processor with a footprint of only 20mm x 30mm and can be readily adapted to fit different server designs, enclosures and component layouts. Liquid cooling is seen as the next important step in data centre servers; 50% of the energy currently used in these installations is for cooling, so more effective and efficient liquid cooling offers the ability to significantly increase the computing capacity in the same available space.

New cooling techniques in the defence sector

Another current example of how these new cooling techniques are now being adopted comes from the defence sector where liquid cooled ATR enclosures are being widely used in real-time computing installations supporting pilot vision systems and advanced radar technology. These applications have a high processing power requirement and consequently produce a lot of heat.

Boston Design Consultants based in Northampton, in partnership with IPECO Group, has developed innovative cold wall technology specifically for ATR applications in the defence sector. The cooling capacity on a ½ ATR short enclosure increases by a factor of 4 to 1,200W using its design of cold wall compared with just 350W using a typical air cooled system.

BDC believes that cooling capacity could be extended even further using higher liquid flow rates; 2,500W may be achievable, over seven times the capacity of air cooling. In addition the temperature gradient across the enclosure is reduced, ensuring that none of the electronics components approach the designed maximum operating temperature.

This improved thermal management has added benefits with electronic components operating at lower temperatures and being subjected to less thermal cycling, MTBF rates extend, resulting in reduced inventory - a very significant cost saving.

But how is the liquid in the cold walls connected to the heat exchanger circuit?

BDC selected Stäubli as its connector supplier, recognising the company's superior technology. Ian Day, director at BDC, commented, "We needed connections that could be guaranteed to be leak free and still easy to use, only Stäubli were able to meet these requirements. Working with their experienced engineers gave us the confidence that a robust, reliable, totally leak free system was achievable and capable of being easily adapted for any cooling medium."

As illustrated by BDC's cold wall technology for ATRs and Thermacore's developments for cooling data centre electronics, Stäubli Connectors has made the move to liquid cooling of electronics far easier to implement than many expected. The company's product specialists are able to provide advice on the precise connector solution and configuration to meet any application. Stäubli is the ideal partner when considering liquid cooling of electronics; within the group there is a wealth of knowledge and expertise in both fluid and electrical connectors available from the design stage onwards.