High power electronic systems used in many commercial and defence applications are outstripping the capability of air cooling; the move to higher capacity liquid cooling has already started, bringing additional challenges of safe fluid handling, eliminating leaks and retaining the ability to disconnect and reconnect electronic circuits without the need for special tools, training or equipment.
Higher processing speeds, increased component and power density in electronic systems result in more heat, higher junction temperatures and increased risk of failure. Traditionally, air-cooling has been applied to electronics, using a combination of heat sinks, heat pipes and fans to remove the heat produced. Modern electronics now being used in data centres, military radar systems and high power computers are rapidly outstripping the capability of forced air cooling systems; couple that with the growing requirement to fully enclose electronics for use in all environments and a change of thinking is needed.
Liquids possess a much higher thermal capacity than air, significantly increasing the capability of a cooling system. Liquid cooling techniques range from spray cooling and micro-channel cooling to cold walls and heat pumps. Each technique requires reliable and efficient fluid circuit connections that can be disconnected and reconnected without draining and prevent any fluid loss or ingress of dirt and dust into the system. Mixing fluids and electronics together could potentially be a problem; high integrity, clean break connectors designed specifically to operate in these most demanding applications become essential.
Sealed electronics enclosures are particularly difficult to cool effectively by air. Air cooling systems tend to be noisy, bulky and unreliable, requiring regular maintenance. Liquid cooling techniques remove these concerns allowing the enclosures to be completely sealed eliminating dust and excluding any contamination from air. Liquid cooled systems are also much quieter than conventional forced air cooling as there are no fans on the device.
The technology of spray cooling continues to be developed; a non-conductive dielectric liquid is sprayed in a fine mist over the hot areas. The phase change associated with evaporation of the fluid on contact with the hot surface provides a very efficient direct cooling system. The evaporated liquid is then cooled via a heat exchanger and returned to the circuit in a closed loop. High performance fluid connections are required to ensure circuit integrity.
In cold wall cooling, coolant is pumped through channels in metal cold plates, adjacent to the heat source; these can be both direct and indirect. Typically in an indirect system the electronics enclosure is cooled by a process of conduction from the circuit board to the cold wall. Heat pipes are used to improve the efficiency of this internal transfer from the electronics. In direct cooled systems, electronic components are mounted directly onto a liquid cold plate. The liquid subsequently passes through a heat exchanger and is recycled.
The main difficulty with liquid cooling of electronics is the ease of connection and disconnection. In the case of line replaceable items, this has to be carried out quickly with no loss, spillage or contamination and without the use of specialist tools or equipment. For individual direct cooled systems, the internal connection is critical to success, again simple plug in cards are required, with even higher constraints on spillage. The use of quick release self-sealing fluid connectors is necessary to achieve all of these requirements. Conventional quick release connectors can be bulky, heavy and difficult to use. They often take up valuable space and add additional weight. Specialist companies, like Stäubli can reduce all of these risks and provide high integrity leak free, spill free fluid connections for the most demanding applications.
The move towards liquid based cooling to accommodate higher power density and processing speeds calls for reconsideration on how these new fluid based systems can be incorporated into devices. Stäubli’s range of high performance quick release connectors is ideal for these demanding applications. They ensure that nothing is introduced into the circuits, prevent any spill on disconnection and can be readily and easily connected and disconnected. They are making the move to liquid cooling of electronics easier and less of a problem than many expected.