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Liquid Cooing: Powerful Cooling for Today's Data Center
Abstract
Organizations are increasingly evaluating and implementing
liquid cooling solutions to meet the heat challenges of blade
servers and high-density computing. Liquid cooling solutions
utilize air/liquid heat exchangers to provide quiet, uniform,
effective cooling.
Many IT professionals list cooling as a top issue in
data
center management, as excess heat and high temperatures
can shorten equipment lifespan, cause system downtime, and negatively
affect equipment performance. As organizations add blade servers
to their IT infrastructure, server rooms and datacenters demand
more electricity and produce more heat, with some high-density
racks exceeding 30 kW and some experts estimating up to 50 kW
per server rack, within the next five years. (1)
Power and Cooling Trends
The increasing power and cooling demands of new equipment increase
costs to levels so high that they may largely offset the financial
and productivity benefits of the equipment. Some experts estimate
that over a server's three-year lifespan, its power and cooling
costs may be greater to or equal to the cost of the equipment
itself. (2) In addition, the high heat loads in many
datacenters make it difficult or impossible to accommodate new
equipment purchases, restricting expansion and limiting the
growth of organizations and businesses.
To meet the challenges of blade servers and high-density computing,
organizations need effective cooling and heat management solutions,
and many are turning to liquid cooling. These solutions utilize
air/liquid heat exchangers to provide quiet, uniform, effective
cooling and isolate equipment from the existing HVAC system.
Liquid cooling is a powerful alternative to ambient air cooling,
as water can carry about 3,500 times more heat than air.
(3) While water is often used in liquid cooling,
liquid refrigerants can be used as well, as their heat transfer
properties are similar to water.
Liquid Cooling: Past and Present
Historically,
liquid cooling
solutions were successfully and safely used to cool high-heat
mainframe computers. Yet, as power consumption and densities
fell to less than 5 kW per rack, air cooling became the standard
technology. With the increasing need to again turn to liquid
cooling the American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE) recently published a book entitled "Liquid
Cooling Guidelines for Datacom Equipment Centers" that discusses
standards and technologies related to datacenter liquid cooling,
designs, and implementations.
Current Liquid Cooling Solutions for the Datacenter
There are several types of liquid cooling solutions that are
being used in datacenters:
- Modular Liquid Cooling Units: These solutions are used
within a fully sealed cabinet and are mounted at the rack
base, in a rack "side car" with cooling modules that can
provide a total cooling capacity of 30kW.
Rittal offers several Liquid Cooling Packages that utilize
variable speed fans and controlled water flow based on real-time
heat load within the rack.
- Door Units: Door solutions feature full-door units that
replace a standard server rack door and contain sealed tubes
filled with chilled water.
- Integrated Rack-Based Liquid Cooling: Integrated solutions
incorporate a rack-based architecture that integrates UPS
power, power distribution, and cooling and feature a cooling
distribution unit (CDU) that pumps water through aluminum/plastic
tubing to coils to cool servers.
- Liquid Cooling/Heat Exchangers for Hot Spots: These
solutions utilize heat exchangers fed by chilled water or
liquid refrigerant to blow cool air directly into hot spots
using the same liquid coolant used by the CRAC units in
the room. (4)
- Device-Mounted Liquid Cooling: There are solutions available
that work at the device level, with coolant routed through
sealed plates on the top of a CPU. As the liquid (dielectric)
takes heat from the device, it turns to gas and is then
exhausted into the hot isle.
Liquid Cooling Considerations
In general, when datacenter managers are considering implementing
a liquid cooling solution, they will want to take into account
a variety of factors, including room humidity, condensation,
and temperature; possible water/refrigerant piping corrosion
issues; and flooring surface. In addition, if water (rather
than liquid refrigerant) is used, ASHRAE recommends that the
water be soft, deionized, distilled, or treated with reverse-osmosis
(5). It is also important to consider current and
anticipated future heat load and access/connections to adequate
and reliable electrical and water/refrigerant supplies.
Datacenter Air Flow Diagram
Implementing Liquid Cooling Solutions in Your Datacenter
Our consultative sales team can help guide you through the process
of implementing a liquid cooling solution in your datacenter.
The team at 42U specializes
in needs assessment, solution design, and implementation support
to ensure that IT professionals maximize their use of current
technologies to improve overall business performance. 42U provides
complete server management solutions, including
KVM over IP,
intelligent power,
environmental
monitoring, rack cooling, and rack mount solutions. A 42U
sales engineer can help you improve your data center performance
by helping you select solutions that are most appropriate for
your organization's particular needs and environment.Liquid
Cooling Products:
Liquid Cooling References:
(1) Brill, K. (2005) "2005-2010 Heat Density Trends in Data
Processing, Computer Systems and Telecommunications Equipment."
Uptime Institute.
http://www.upsite.com/file_downloads/PDF/TUI_WPapers_0506/TUI691_2005_2010HeatDensity_WP.pdf.
See Also: Mitchell, Robert, (2007)"The Liquid Data Center."
CIO Magazine
(source:
Computerworld Today, Australia.)
(2) Brill, K. "High Density Computing: The Path Forward 2006."
Uptime Institute.
http://www.upsite.com/TUIpages/downloads/(TUI3003SYM6)TPFExecSumm.pdf
See also: Brill, K "Data Center Energy Efficiency and Productivity"
http://www.uptimeinstitute.org/symp_pdf/(TUI3004C)DataCenterEnergyEfficiency.pdf
(3) Stansberry, Matt. "Liquid cooling book promotes standardization"
SearchDataCenter.com
http://searchdatacenter.techtarget.com/originalContent/0,289142,sid80_gci1218484,00.html
(4) Mitchell, Robert, (2007). "The Liquid Data Center." CIO
Magazine
http://www.cio.in/news/viewArticle/ARTICLEID=2876 (source:
Computerworld Today, Australia.)
(5) ASHRAE, (2006). "Liquid Cooling Guidelines for Datacom Equipment
Centers" ISBN-10: 1-933742-05-4; ISBN-13: 978-1-933742-05-2.
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write to us.
42U's Vision is to inspire corporate responsibility in energy efficiency and be a leader in providing technology and vendor agnostic information, suggestions, and solutions for making data centers more energy efficient.
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