Although people usually aim to keep liquids away from electronics, liquids are an essential thermodynamic tool for ensuring adequate heat transfer away from heat generating components in various applications. Specially designed liquid-cooling systems not only maintain optimal operating temperatures they can enhance the performance of electronics, especially high-density electronics such as those found in large network server centers.
Liquid-cooling systems have several advantages. They are fully enclosed systems with less noise generation, lower power consumption, and higher heat transfer rates compared to those of traditional air-cooling systems. A custom liquid cooling system is often designed to fit the density of electronics in a small space while working within architectural constraints. Custom designed systems also offer spot cooling options to ensure even the hottest electronic parts stay cool and hot-swappable components to minimize down time.
Liquid cooling is not a new technology; it is prevalent in engines and power generation. An automobile keeps its engine cool by circulating antifreeze between the engine the radiator. Spacecraft and satellites operate where no air is available so they use liquid cooling for electronics. In the early 2000s, PC hobbyists and gamers used liquid cooling to keep their CPUs cool, allowing them to overclock the CPUs and run them at maximum speeds.
Modern high-speed electronics generate a lot of heat, and they are often housed in densely packed data centers. Liquid cooling is necessary to ensure optimal thermal performance in these facilities.
In contrast to liquid cooling systems, air-cooling systems blow cool air over hot components. Through convection, the part cools while the air warms. The rate of cooling is dependent on the temperature difference between the incoming air and the part and rate the air is blown. Although heat sinks can enhance air cooling performance, generally speaking, air is not a great conductor, and it has low heat capacitance. These thermal limitations, coupled with the mechanical limits of fans and blowers means air cooling can only do so much to keep electronics cool.
Air cooling systems are open systems requiring a ready source of filtered, cool ambient air and somewhere to dump the warm air to an outside space without warming intake air. Fast moving air, as well as the associated fans and blowers, are also noisy, and the airflow can be disruptive.
On the other hand, liquids such as water and other thermally conductive fluids have higher heat capacitance and conductivity than air. They require lower flows to achieve higher heat convection rates. The caveat is that with few exceptions, liquids don’t play nice with electronics.
The key to liquid cooling is keeping the electronics separated from the liquid. Electronics are mounted to cold plates, specially designed hollow plates that allow liquid to flow between an inlet and an outlet. The hollow cavity is designed to ensure known hot components are spot cooled. Cool liquid flows into the plate, the heat conducted from components warms, and warmer liquid flows out. Unlike direct air cooling, which is convection only, liquid cooling systems rely on conduction and convection for heat transfer.
An advantage to isolating the liquid from the components is that the liquid can be pumped in a closed cooling loop. Warm liquid is pumped through a cooling unit, then cool liquid flows through piping and the cold plates before it is returned to the pump. A noisy pump and cooling unit can be in a sound isolating enclosure or another room. The cooling unit might be either a radiator or refrigeration depending on the cooling needs.
A liquid cooling system can also be configured so that when a section of electronics requires service or replacement, they can be disconnected and removed without disrupting the rest of the system – meaning the components are hot-swappable.
When it comes to implementing a liquid cooling system, IT departments consider many design requirement, including:
These design considerations are typical of any cooling system; however, liquid cooling systems have the added complexity of a closed loop fluid pumping system.
Using an off-the-shelf liquid cooling system might seem attractive, but one size does not fit all. Often these systems are difficult and costly to adapt existing electronics. Custom cooling solutions are better suited to address design requirements. An implementation partner specializing in custom fluid transfer solutions is often used to design a custom liquid cooling system.
Pumps, cooling units, plumbing, and connectors are custom configured alongside custom-designed cold plates. The system may be designed with multiple parallel fluid circuits. Plumbing is selected to meet space constraints, allow for reconfiguration and expansion, and facilitate efficient flow through the system. The pump is chosen to meet liquid flow and pressure drop needs. Connectors, such as quick disconnects, are selected to facility hot-swappable components.
As previously mentioned, the key to a liquid cooling system is keeping the electronics separated from the liquid. Leaks are a natural concern – they pose an obvious point for potentially catastrophic failures.
In an ideal situation, a liquid cooling system is leak free, and component never has to be swapped out. Unfortunately, this ideal situation is not practical. Components require service, and as demand for more data goes up, data centers must be flexible and expandable.
While companies opt for custom liquid cooling systems, they often stop short at the connectors. Although couplings and connectors are critical for ensuring flexibility and expandability, there is greater risk of leakage when couplers are selected that have not been designed for liquid cooling applications. Typically, standard-sized, off-the-shelf fluid couplings, and quick disconnects are used.
However, couplings and connectors must be accessible to enable hot-swappability for both day-to-day maintenance and emergencies. Using off-the-shelf quick disconnects might compromise these essential design requirements and pose a potential leak hazard. When off-the-shelf couplers are insufficient, custom couplers offer more design flexibility to meet design needs.
SafeWay, a division of The Specialty Manufacturing Company, offers custom ISO-certified quick disconnects to maximize the performance of custom liquid cooling systems. SafeWay’s quick disconnects are flush face, dry break couplings with optional sleeve locks to prevent accidental disconnect. Multiple connection combinations are available, and they can be color coded for easy identification.
To compliment a custom cooling system design, SafeWay is a flexible and collaborative partner. We work with your design team to ensure our custom solutions meet your thermal management challenges.
Have questions? Contact us.