The role of quick disconnect couplings in liquid cooling ...

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The role of quick disconnect couplings in liquid cooling:
Five attributes that contribute to connector reliability

By The use of liquid cooling to mitigate heat Traditionally, data centers have relied on
David Vranish generated by electronics can be found in a air for cooling. However, forcing cold air
wide variety of applications, including gaming through server racks is an inefficient and
Applications Engineer computers, supercomputers and medical costly method to remove heat. Sixty percent
Colder Products Company equipment. But the widest acceptance of the of cooled air is lost as by-pass and through
technology is in today’s data center industry, air mixing, and cooling costs can exceed the
where server manufacturers are turning to liquid costs of running the servers. As computer
cooling for cost-efficient and effective thermal servers are pushed to run faster and data
management. Here, in particular, quick disconnect center rack densities increase, it is becoming
couplings are playing an integral role in cooling impractical to expect moving air to provide
system performance and reliability. sufficient cooling.

Implementing an efficient, effective and Water, on the other hand, is 3,500 times
safe cooling system to remove waste more effective than air2 on a volume basis
heat is an ever-growing concern for data at storing and transferring heat. In fact,
centers. Energy consumption by servers 41 percent of respondents in a recent
has risen dramatically within the last industry-wide survey expect a combination
decade as power densities of server racks of air and liquid to be the primary
have increased. While server racks of a method of data center cooling.3 Liquid
decade ago consumed 250 W to 1.5 kW cooling represents the best alternative to
each, current power racks consume around raising cooling efficiency and reducing air
10 kW. Projections for the next decade put conditioning costs.
power consumption at 50 kW. Further, it
is estimated that, by 2020, the data center Using liquid to cool computers goes back
industry will generate as much CO2 as the to the mid-’60s when IBM implemented
airline industry.1 liquid cooling for its 704 mainframe. Nearly
50 years later, IBM recently employed
processor-level liquid cooling for a
supercomputer located at a Swiss university,
where water is circulated to cool the
processors and then pumped to the under-
floor heating system where the waste heat
can be used for building heat. Compared
with air-cooled servers, IBM estimates that
the liquid-cooled system uses 40 percent
less energy, and the additional use of the
waste heat lowers carbon footprint by an
estimated 85 percent.4

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Page 2 LIQUID COOLING
Figure 1: Advantages of liquid cooling

AIR COOLING

Liquids are 3,500-4,000 times more efficient at transferring heat

Significant cost savings result from more efficient cooling
Energy use required for cooling is reduced
Noise is reduced due to slower fan speeds required for cooling
Carbon footprint is reduced 85 percent through a reduction in waste heat

A CRITICAL COMPONENT FOR LIQUID COOLING entire server rack to fail. This puts a critical
RELIABILITY focus on the design, construction and
quality of the quick disconnect coupling.
One of the critical components in liquid
cooling systems is the quick disconnect When selecting quick disconnect couplings
coupling. These couplings are used to link for liquid cooling of servers and other high-
together flexible tubes that carry cooling end computers, it is important to look for the
liquid to individual servers and central following five attributes to ensure reliability.
manifolds on the server rack connected to
central heat exchangers (see Figure 2). The 1. Robust design and construction Figure 2: Quick disconnects for server
critical contribution of quick disconnect cooling
couplings becomes more evident when Liquid cooling system quick disconnect
considering that these couplings need to couplings need to be durable and robust.
stay reliably connected for long durations They also need to be designed for low-
but then disconnect easily without valve pressure applications and able to withstand
failure. Furthermore, when servers need to long periods of connection before being
be serviced or changed out, the couplings disconnected. Couplings should also be
must easily disconnect without dripping or designed for low pressure drop in order to
spilling coolant on sensitive electronics. minimize flow restriction and the burden on
cooling system pumps.
The chief concern of server designers and
data center operators is system reliability. Some liquid cooling systems employ
According to the Ponemon Institute, the couplings developed for the hydraulics
average cost for any type of data center industry because of their perceived higher
outage is more than $690,000.5 One of the durability. However, the seals and internal
basic methods of achieving high reliability valves of these couplings were not designed
is through redundant components that take for low-pressure applications and where
over if primary components fail. In liquid couplings are required to be connected
cooling systems, redundant pumps are often for months or years at a time. When
employed to prevent loss of circulation. selecting quick disconnect couplings for
However, individual quick disconnect liquid cooling systems, look for couplings
couplings in the cooling system represent a that are designed specifically for low-
single point of failure. A faulty connector pressure applications and feature robust
has no backup, so a leak might cause the construction.

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Page 3

2. “Dry disconnect” capability Technicians accustomed to connecting CPC has designed a new series
and disconnecting Ethernet of ultra-reliable, dripless quick
Technicians need to be able to easily connections and power cables will disconnect couplings specifically
disconnect cooling loops from servers have little trouble with intuitively for liquid cooling of electronics.
without risk of water or other coolant designed quick disconnect couplings. LQ Series connectors are the first of
leaking on to sensitive electronics. their kind, incorporating a patent-
4. Resilient seals pending, flush-face valve technology
Quick disconnect non-spill couplings that allows the couplings to be
can feature two styles of internal Couplings used in liquid cooling connected for long periods — and
valves that automatically shut off the applications remain in a connected then easily disconnected without
flow of liquid when the couplings are state for extended periods. Upon dripping cooling fluid on sensitive
disconnected. One style of double- disconnection and reconnection, they electronic components. The couplings
shutoff coupling features poppet valves need to function perfectly so there are designed to withstand long-term,
that, by virtue of their design, trap are no drips or leaks of coolant. Seals repeated use and feature color-coded
a small amount of liquid within the that are not properly formulated or rings to ensure accurate cold-side
coupling body. This liquid can drip designed can take a “set” that causes and return-side connections. Multiple
out when the coupling is disconnected. leaks upon disconnection. The seals options for materials, configurations
While the leakage is not a large also have to be compatible with and sizes plus custom solutions are
amount — likely just a drop or two — the cooling liquid to prevent seal available to meet any liquid cooling
it might be sufficient to raise safety or swell, shrink, brittlement or other application.
reliability concerns around electronics. distortions. In some cases, couplings
may feature dual seals to enhance
In contrast, true dry-disconnect sealing capabilities in the quest for
couplings feature flush-face valves higher reliability. However, dual seals
that allow no more than a coating of can introduce greater friction to the
cooling fluid on the valve surfaces. system and might actually reduce
This virtually eliminates the possibility reliability if not designed properly.
of dripping onto vital components.
Look for couplings that feature 5. Materials compatibility
precision-made, internal flush-
face valves and, ideally, couplings Most plastics and metals are
designed specifically for liquid cooling compatible with cooling liquids such
applications. as water-glycol mixtures. However, if
your cooling system uses a proprietary
3. Ease of use cooling liquid, be sure to determine
whether the coolant is compatible
It is important to be able to easily with coupling housings, seals, valves
disconnect the cooling loops from and tubing. Use particular caution
servers with no spills. Whether it when selecting metal couplings for
is a push-to-connect or twist-lock the cooling system that might come
type of coupling, the valves need to into contact with a server chassis, as
reliably close when disconnected, dissimilar metals can create electrolysis
even after having been connected and corrosion where they touch.
for months or years. Another aspect Couplings developed from metal ball-
of ease of use is the availability of and-sleeve hydraulic couplings are
color-coded couplings, which help not intended to be used for cooling
ensure hot-to-hot and cold-to-cold applications, so materials compatibility
connections. When a cooling system is should be carefully checked.
equipped with properly designed quick Compatibility issues can be avoided
disconnect couplings, it simplifies by using metal couplings designed
maintenance and serviceability. specifically for liquid cooling.

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Page 4 CONCLUSION
Liquid cooling of computers and servers is
Reliable quick disconnect couplings play a the most efficient and cost-effective method
significant role in liquid cooling systems that of dissipating heat generated by today’s
mitigate heat generation at the source. faster and higher-density electronics. By
providing cooling at the source of the heat, air
About CPC conditioning demands can be reduced along
A leader in connection technology, with the attendant costs and carbon impact.
CPC has been delivering quick
disconnect couplings for liquid With cooling system designs still evolving,
cooling of electronics for over it is important to understand the role that
20 years. Applications for CPC’s quick disconnect couplings play in these
liquid cooling connections include systems and how they contribute to system
PCs, supercomputers, data centers, reliability. Evaluating couplings based on
chillers, medical equipment and their robustness, valves, seals and materials
many others that require quality compatibility can help ensure long-term
and performance for critical fluid performance. To make the best choice for
handling solutions. Our dripless your application, work with a coupling
quick disconnect couplings feature supplier that understands the demands of
automatic non-spill shutoff valves liquid cooling and can offer a wide selection
and integral terminations for safety, of couplings, including purpose-built cooling
ease of use and reliability. CPC couplings and custom design capabilities.
offers multiple options for materials,
configurations, sizes and valves References:
and custom solutions to meet 1. Data Center Journal, “The Green Data
unique needs.
Center Opportunity,” (February 2012).
Smart fluid handling to take you forward, faster. 2. Office of Energy Efficiency & Renewable

© 2014 Colder Products Company. All rights reserved. Energy, “Quick Start Guide to Increase
Data Center Efficiency,” (2008).
3. “Data Center 2025: Exploring the
Possibilities,” (February 2014).
4. CNET, “IBM Liquid-Cooled Super-
computer Heats Building,” (May 2010).
5. Mission Critical, “Power and
Management Best Practices for
Enterprise Data Center Design,”
(March/April 2014), pp. 32-38.

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