ASHRAE Journal - July 2019 - 21

TECHNICAL FEATURE

J U LY 2 0 19

ashrae.org

ASHRAE JOURNAL

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Cooling Load (kW/ft2)

can provide a more uniform cooling
FIGURE 1 Water Cooling Load Trends from 2010 to 2017. Footprint includes apportioned CDU area. Data shown
of the components compared to air
with permissions from HPE, SGI, Fujitsu, IBM, Dell, Huawei and Cray.
cooling, improving the reliability of
the system.
14
With these factors in mind,
24
Air
Scientiﬁc Servers
Indirect
12
ASHRAE TC 9.9, Mission Critical
(2018 Air Cooling Power Trends)
Direct
Facilities, Data Centers, Technology
10
Maximum Facility Supply Temperature in °C
Spaces and Electronic Equipment,
8
has recently published a 45-page
27
10
32 32
white paper "Water-Cooled Servers-
40
6
45 25 32 32 20
32
24
25
Common Designs, Components,
16
4
45 16
16 16
40
and Processes" (available for free at
20
16 10
40
16
45
45
45
https://tinyurl.com/y239t4rv). With
2
the advent of more water-cooled
0
IT products arriving in the market2010
2011
2012
2013
2014
2015
2016
2017
Year
of
Announcement
place, TC 9.9 felt the need to outline
some of the common processes,
parts and materials that could provide focus for use in
axis is the server power divided by the rack footprint.
future water-cooled designs and help accelerate the
Variations in rack height are not accommodated in this
trend toward increased use of water-cooled servers
ﬁgure, but it is noted that there was not a large variadeployed in data centers.
tion of rack heights. One other caveat in the denominaObviously, some parts in a water-cooled IT system will
tor for the area is that if the water-cooled server rack
be speciﬁc to the product design, such as cold plates,
required a coolant distribution unit (CDU) (see the secmanifolds, arrangement of piping, pumps, valves, etc.,
tion below for a description of the CDU implementabut some things like quick connects, hoses, hose contion into a data center) then this area was apportioned
nections, wetted materials, ﬁltration, pressure testing
to the rack area. For example, if a CDU supported
of ﬁnal water-cooling assemblies, water chemistry and
four server racks then 25% of the area of the CDU was
design options to integrate water-cooled IT equipment
added to the rack area to make up the denominator for
into the data center cooling infrastructure fall more
power/rack footprint.
into the category of common parts/processes that could
Each bar in Figure 1 displays the total maximum heat
be used by all current and potential manufacturers of
load dissipated by the water-cooled server rack. (For
water-cooled IT equipment.
comparison, the trend of the maximum air-cooled servThe TC 9.9 white paper effort is an attempt to provide
ers [scientiﬁc servers] as displayed in the latest ASHRAE
and make available those items that could be classiDatacom Series book IT Equipment Power Trends, 3rd Edition
ﬁed as common. Several of these will be discussed in
is also shown in Figure 1.) The amount of power dissithis article. The remainder of this article, as well as
pated is categorized into three areas: air cooled, indirect
the white paper, are focused on the implementation of
water-cooled and direct water-cooled. These are deﬁned
water-cooled IT equipment. Other liquid-cooling techas follows:
nologies for IT equipment are available, and in general
* Air Cooled: power that is transferred directly to the
these liquids will be associated with the technology cool- room air and cooled via traditional data center cooling.
ing system loop (TCS) for the IT equipment, while the
* Indirect Water-Cooled: power that is transferred inwater-cooled facilities loop (facility water system [FWS]) directly to water through an air-to-water heat exchanger
will still be required to remove the heat from the liquid- located within or on the rack (for example, a rear door
cooled TCS loop.
heat exchanger).
The data in the white paper displays some trends,
* Direct Water-Cooled: power that is transferred
including that of 28 water-cooled products announced directly to an attached heat transfer component like a
by IT OEMs from 2010 to 2017 (Figure 1). The vertical
cold plate.

https://www.tinyurl.com/y239t4rv https://www.ashrae.org/

ASHRAE Journal - July 2019

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