ASHRAE Journal - August 2021 - 45

TECHNICAL FEATURE
FIGURE 1 Room-based air distribution methods. (a) Uncontained raised-floor, (b) hot-aisle containment and (c) cold-aisle containment.
A.
B.
C.
RA
RA
Bypass
Hot Spot
CRAH
Server
Racks
(Hot Aisle)
SA
Server
Racks
Server
Racks
(Cold Aisle) (Hot Aisle)
Raised Floor
(Cold Aisle)
CRAH
(Cold Aisle)
SA
Server
Racks
Server
Racks
(Hot Aisle)
Raised Floor
traditional uncontained data centers.5 Many data centers
use HAC or CAC to improve thermal performance
and cooling effi ciency (Figure 1). Which is the better air
distribution system for legacy data centers? In reality,
the best air containment type will largely depend on the
constraints of the facility. The HAC or CAC results in the
following fi ve effi ciency benefi ts:1
1. A higher supply air (SA) temperature is available in
cooling systems: an uncontained room-based cooling
system is set to a much lower SA temperature (i.e., approximately
13°C [55°F]) lower than the level required in
the IT equipment room to prevent hot spots.
2. Elimination of hot spots: the SA temperature can be
the same as the inlet air temperature (18°C to 27°C [64°F
to 81°F]) of IT equipment. The HAC or CAC system allows
cooled SA of the computer room air conditioning/
handling (CRAC/H) unit to reach the air inlet of the IT
servers without air mixing.
3. Energy savings: as the SA temperature can increase,
cooling systems can operate a larger number of economizer
hours without mechanical cooling.
4. Reduction of humidity controls: cooling systems can
increase the SA temperature to operate above the dewpoint
temperature. There is no need to remove humidity
from the air and to add humidity to the air.
5. Rightsizing of cooling system with higher effi ciency:
oversizing cooling infrastructure has larger constant
losses than rightsizing cooling infrastructure. These
fi xed losses are independent of load.
The CAC system encloses the cold aisles, and the
rest of an IT room becomes a large hot air return path
Server
Racks
(Cold Aisle)
(Hot Aisle)
CRAH
(Hot Aisle)
SA
Server
Racks
Server
Racks
Server
Racks
(Cold Aisle) (Hot Aisle)
Raised Floor
(Cold
Aisle)
Recirculation
RA
including ducts. The cold air and hot airfl ows are separated
by enclosing the cold aisles. The HAC system
encloses the hot aisles and isolates the hot air from IT
equipment, and the rest of the IT room becomes a large
cold air supply path including a raised fl oor. By enclosing
the hot aisles, the hot and cold airfl ows in the IT
room are separated. Solutions to seal the cold and hot
aisle with partitions made of various materials can be
implemented.
Air containment is an established and effective means
of improving airfl ow management within IT rooms. The
leakage of a traditional uncontained confi guration with
raised fl oor is typically 25% to 50%, whereas the leakage
of an aisle containment system is typically 3% to 10%.1
However, even with an air containment system, hot
spots occur in many data centers. Poor air distribution
can result from air leakage in an air containment system.
Common problems include recirculation, bypass
and negative pressure. Moreover, unused vertical space
within rack enclosures causes the hot air output from
equipment to fl ow back to the inlet of the equipment.6
Methodology
This study is composed of two parts. The fi rst part
deals with the numerical simulation, and the second
part is devoted to experimental investigation. An experimental
characterization of air containment was carried
out at a telecom data center in Korea along with detailed
numerical modeling. The ultimate goal is to compare
both air containment systems to see if any differences
A U G U S T 2 0 2 1 ashrae.org ASHRAE JOURNAL
45
http://www.ashrae.org

ASHRAE Journal - August 2021

Table of Contents for the Digital Edition of ASHRAE Journal - August 2021

Contents
ASHRAE Journal - August 2021 - Intro
ASHRAE Journal - August 2021 - Cover1
ASHRAE Journal - August 2021 - Cover2
ASHRAE Journal - August 2021 - 1
ASHRAE Journal - August 2021 - Contents
ASHRAE Journal - August 2021 - 3
ASHRAE Journal - August 2021 - 4
ASHRAE Journal - August 2021 - 5
ASHRAE Journal - August 2021 - 6
ASHRAE Journal - August 2021 - 7
ASHRAE Journal - August 2021 - 8
ASHRAE Journal - August 2021 - 9
ASHRAE Journal - August 2021 - 10
ASHRAE Journal - August 2021 - 11
ASHRAE Journal - August 2021 - 12
ASHRAE Journal - August 2021 - 13
ASHRAE Journal - August 2021 - 14
ASHRAE Journal - August 2021 - 15
ASHRAE Journal - August 2021 - 16
ASHRAE Journal - August 2021 - 17
ASHRAE Journal - August 2021 - 18
ASHRAE Journal - August 2021 - 19
ASHRAE Journal - August 2021 - 20
ASHRAE Journal - August 2021 - 21
ASHRAE Journal - August 2021 - 22
ASHRAE Journal - August 2021 - 23
ASHRAE Journal - August 2021 - 24
ASHRAE Journal - August 2021 - 25
ASHRAE Journal - August 2021 - 26
ASHRAE Journal - August 2021 - 27
ASHRAE Journal - August 2021 - 28
ASHRAE Journal - August 2021 - 29
ASHRAE Journal - August 2021 - 30
ASHRAE Journal - August 2021 - 31
ASHRAE Journal - August 2021 - 32
ASHRAE Journal - August 2021 - 33
ASHRAE Journal - August 2021 - 34
ASHRAE Journal - August 2021 - 35
ASHRAE Journal - August 2021 - 36
ASHRAE Journal - August 2021 - 37
ASHRAE Journal - August 2021 - 38
ASHRAE Journal - August 2021 - 39
ASHRAE Journal - August 2021 - 40
ASHRAE Journal - August 2021 - 41
ASHRAE Journal - August 2021 - 42
ASHRAE Journal - August 2021 - 43
ASHRAE Journal - August 2021 - 44
ASHRAE Journal - August 2021 - 45
ASHRAE Journal - August 2021 - 46
ASHRAE Journal - August 2021 - 47
ASHRAE Journal - August 2021 - 48
ASHRAE Journal - August 2021 - 49
ASHRAE Journal - August 2021 - 50
ASHRAE Journal - August 2021 - 51
ASHRAE Journal - August 2021 - 52
ASHRAE Journal - August 2021 - 53
ASHRAE Journal - August 2021 - 54
ASHRAE Journal - August 2021 - 55
ASHRAE Journal - August 2021 - 56
ASHRAE Journal - August 2021 - 57
ASHRAE Journal - August 2021 - 58
ASHRAE Journal - August 2021 - 59
ASHRAE Journal - August 2021 - 60
ASHRAE Journal - August 2021 - 61
ASHRAE Journal - August 2021 - 62
ASHRAE Journal - August 2021 - 63
ASHRAE Journal - August 2021 - 64
ASHRAE Journal - August 2021 - 65
ASHRAE Journal - August 2021 - 66
ASHRAE Journal - August 2021 - 67
ASHRAE Journal - August 2021 - 68
ASHRAE Journal - August 2021 - 69
ASHRAE Journal - August 2021 - 70
ASHRAE Journal - August 2021 - 71
ASHRAE Journal - August 2021 - 72
ASHRAE Journal - August 2021 - 73
ASHRAE Journal - August 2021 - 74
ASHRAE Journal - August 2021 - 75
ASHRAE Journal - August 2021 - 76
ASHRAE Journal - August 2021 - 77
ASHRAE Journal - August 2021 - 78
ASHRAE Journal - August 2021 - 79
ASHRAE Journal - August 2021 - 80
ASHRAE Journal - August 2021 - Cover3
ASHRAE Journal - August 2021 - Cover4
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2021november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2021november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XCODFR
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QSLFGO
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ILKVNM
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2021
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OPDJKD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VJKSRY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SDHUTC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JPPKRR
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SDLTTH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_CKLLES
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SLDOX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_HJETUK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OLUHGE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2020october
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2020october_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ZERDGH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QVMNEO
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RTPOKE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_BBATRE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_STUBMW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TPEMPE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JNMKDS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FBTTPA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WQMMNE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TVBRYN
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2020
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_KTUZMA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ABEDGD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201910
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201909
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019septmeber_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019september
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201908
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201907
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201906
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201905
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201904
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019april
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201903
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019march
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201902
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201901
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2019
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018december
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018october
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2018
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201810
https://www.nxtbook.com/nxtbooks/ashrae/ashraeinsights_201806
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201805
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201804
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201803
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201712
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201711
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201710
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201709
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201705
https://www.nxtbook.com/nxtbooks/ashrae/ashrae_meetinginsert_201610
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acrexindia
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer
https://www.nxtbook.com/nxtbooks/amca/2014summer2
https://www.nxtbook.com/nxtbooks/amca/2014summer
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acma_2014summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201311
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201309
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acmasupp_2013fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201305
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201303
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2013winter
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201211
https://www.nxtbook.com/nxtbooks/ashrae/achr_expo_mexico2012
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201209
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v3
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v2
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201205
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201203
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012winter
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201111_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201109_v2
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2011summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201105
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201103
https://www.nxtbookmedia.com