ASHRAE Journal - July 2019 - 56

COLUMN DATA CENTERS

Liquid-Cooling Trends
In Data Centers
BY DONALD L. BEATY, P.E., FELLOW/LIFE MEMBER ASHRAE; DAVID QUIRK, P.E., MEMBER ASHRAE; FRANK T. MORRISON, MEMBER ASHRAE

In previous columns, the use of airside or waterside economizers was explored as a
method to reduce the energy use in datacom facilities. The goal of all these systems,
whether air-cooled or water-cooled, was to provide a cooling airstream to the electronic equipment, which is typically arranged in racks positioned throughout the
facility.
ASHRAE has published thermal guidelines for datacom facilities that allow higher air temperatures in
the conditioned space that can extend the hours of
economization and hence increase the energy savings
substantially. To further improve the efﬁciency of the
cooling system and handle ever-increasing heat loads,
these racks are placed in hot aisle/cold aisle conﬁgurations often with strategically placed blanking plates to
help direct the cooling airstream optimally over the
electronic equipment while simultaneously keeping the
warm leaving air from mixing with the cool incoming
air (Figure 1).
Despite such efforts to improve cooling with air, signiﬁcant growth in heat loads and heat density per rack
has challenged the ability of air to provide adequate,
reliable, and economic data center cooling. Higher
heat loads generated by electronic equipment can have
detrimental side effects, such as reduced equipment
availability, wasted ﬂoor space, and inefﬁcient cooling
system operation. To help meet these ever-increasing
challenges, the use of liquid cooling is growing, prompting ASHRAE TC 9.9 to develop the ASHRAE Datacom
Series book Liquid Cooling Guidelines for Datacom Equipment
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J U LY 2 0 19

Centers, as well as several white papers. Like the thermal
guidelines for datacom facilities cooled by air, ASHRAE
has established a set of temperature guidelines for
liquid-cooled facilities depending on the Liquid Cooling
Class, deﬁned as W1 through W5, as shown in Figure 2.
The overall goals of these liquid cooling implementations include beneﬁts such as:
* Enabling higher rack power densities to decrease
required data center footprint;
* Efﬁciently transferring waste heat to the facility
water system (FWS);
* Allowing liquid-cooling loop temperatures to be as
warm as possible to:
* Increase the efﬁciency of rejecting the heat to
the atmosphere while signiﬁcantly increasing
the hours of economization;
* Enable captured heat to be used for other beneﬁcial purposes;
Donald L. Beaty, P.E., is president and David Quirk, P.E., is vice president of DLB Associates
Consulting Engineers, in Eatontown, N.J. Beaty is a member and Quirk is research subcommittee chair of TC 9.9, Mission Critical Facilities, Data Centers, Technology Spaces
and Electronic Equipment. Frank T. Morrison is technical director, global marketing at
Baltimore Aircoil in Jessup, Md. He is a member of SSPCs 188 and 90.1 as well as TC 8.6.

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ASHRAE Journal - July 2019

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