ASHRAE Journal - August 2021 - 52

TECHNICAL FEATURE
A.
FIGURE 6 IT environment measurement points of temperature and humidity sensors in (a) HAC system and (b) CAC system.
Hot-Aisle Containment (HAC) With Ducted Air Return
T HAC-R-1
CRAH 1H
Supply Air (SA)
1220
HAC-C-1
C-2
Hot Aisle
C-3
C-4
C-5
C-6
C-7
C-8
C-9
C-10
T
B
T
B
T
B
T
B
HAC-S-1 B
1220
Return Air
(RA)
3660
1220
Main Patch
Panel
Main Patch
Panel
1
2
3
4
5
6
7
8
T
B
Cold Aisle
Measurement Sensor:
Cold Aisle
Hot Aisle
Cold Aisle
T Top
B Bottom
Temperature and Humidity Sensor (64 EA)
the HAC was maintained at 15°C (59°F). In Test Case 2,
the supply air temperature of the CAC was maintained
at 15°C (59°F), and in Test Case 3 the supply air temperature
of the HAC was maintained at 17°C (63°F). The
maximum inlet air temperature of all rack servers has
a target of 100% at the ASHRAE recommended range.
For the three test cases that are at the same provisioning
level, nothing changes except the supply air temperature
of the CRAH unit. As shown in Table 4, measurement
conditions were set depending on the SA temperature of
the CRAH units.
Test Case 1: HAC With SA 15.0°C (59°F)
Figure 7a and Figure 8a show the air temperature distributions
of the HAC. When the supply air temperature of
CRAH units was 15.0°C (59°F), the mean temperature of
the air entering the IT equipment in the cold aisle (C-1
to C-20 in Figure 7a) was 20.1°C (68°F) . Thus, approximately
5.1°C (9°F) was lost in the supply air distribution
path. The inlet air temperature of each rack server
met the ASHRAE recommended range, but overcooling
occurred in some areas (C-13, 14, 16, and 18 in Figure 7a).
Furthermore, after heat removal in the rack server, the
mean temperature of the air discharged to the hot aisle
(H-1 to H-10 in Figure 8a) was 26.4°C (79.5°F). Thus, the
52
ASHRAE JOURNAL ashrae.org A U G UST 2021
TABLE 4 Measurements adopted in three test conditions.
TEST
SA
CONDITIONS
Test Case 1
Test Case 2
Test Case 3
TEMPERATURE
15°C
15°C
17°C
AIR CONTAINMENT
Hot-Aisle
Containment
Cold-Aisle
Containment
Hot-Aisle
Containment
temperature differential (ΔT) was approximately 6.3°C
(11.3°F). However, the mean return air temperature of
the CRAH unit was 26.1°C (79°F), indicating some mixing
of cold air and hot air. The average air temperature
in the cold aisle implies that hot aisle air leaked out in
many places and was recirculated.
Test Case 2: CAC with SA 15.0°C (59°F)
Figure 7b and Figure 8b show the IT environment of
the CAC. The mean air inlet temperature of IT servers
in the cold aisle (C-1 to C-20 in Figure 7b) was 22.5°C
(72.5°F) when the CRAH unit's supply air temperature
was 15.0°C (59°F). Thus, approximately 7.5°C (13.5°F)
was lost in the moving supply air path, which was 2.4°C
(4.3°F) more than the HAC.
To Meet the ASHRAE
Recommended Range
Empty
10
T
T
T
T
HAC-H-1
H-6
H-2
H-7
H-3
H-8
H-4
H-9
T
H-10
H-5
T
T
T
T
T
Hot-Aisle
Containment
CRAH 2H
HAC-S-2 B
1220
Main Patch
Panel
Main Patch
Panel
11
12
13
14
15
16
17
18
20
19
T
B
T
B
T
B
T
B
T
B
Supply Air (SA)
1220
610
HAC-C-11
C-12
C-13
C-14
C-15
C-16
C-17
C-18
C-19
C-20
Cold Aisle
1220
Return Air (RA)
CRAH 1C
CAC-S-1
1220
Supply Air (SA)B
3660
1220
Empty
Main Patch
Panel
Main Patch
Panel
CAC-H-1
H-2
H-3
H-4
H-5
T
T
T
1
2
3
4
5
6
7
Empty
Empty
8
T
10
9
T
Hot Aisle
11
12
13
T
B
T
B
T
B
CAC-C-1
C-2
C-11
C-12
T
B
C-3
C-4
C-13
C-14
T
B
C-5
C-6
C-15
C-16
C-7
C-8
C-17
C-18
C-9
C-10
C-19
C-20
T
B
T
B
B. Cold-Aisle Containment (CAC) With Ceiling Plenum Air Return
T CAC-R-1
Return Air (RA)
1220
Empty
Main Patch
Panel
Main Patch
Panel
T
B
14
15
16
17
Empty
Empty
T
B
18
20
19
T
B
Cold-Aisle
Containment
21
22
23
T
T
H-9
H-10
Hot Aisle
Hot Aisle
T
T
CAC-H-6
H-7
Cold Aisle
T
H-8
1220
610
MAXIMUM INLET AIR TEMPERATURE
OF RACK SERVERS
10 980
7320
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
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ASHRAE Journal - August 2021 - 80
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ASHRAE Journal - August 2021 - Cover4
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