ASHRAE Journal - August 2021 - 54

TECHNICAL FEATURE
The inlet air temperature
of each IT server was
within the ASHRAE recommended
range, but hot spot
(C-1 in Figure 7b) and overcooling
(C-12 in Figure 7b)
phenomena occurred in
some areas.
Furthermore, the mean
outlet air temperature of
rack servers in the hot aisle
after IT heat removal (H-1
to H-10 in Figure 8b) was
30.1°C (86.2°F). Thus, the
ΔT was approximately 7.5°C
(13.5°F).
However, the mixing
of air in the room was
analyzed, and the mean
return air temperature of
the CRAH unit was 30.0°C
(86°F).
The air temperature
distribution remained
constant because it was not
affected by external cooling
load and mostly consisted
of IT heat.
However, the mean air
temperature in the cold
aisle was higher than the
supply air temperature,
which implies that a large
airflow rate in the hot
aisle leaked out and was
recirculated.
FIGURE 7 Mean inlet air temperature distributions of rack servers. (a) Test Case 1, (b) Test Case 2 and (C) Test Case 3.
Test Case 1: Hot-Aisle Containment (HAC) with Supply Air Temperature of 15.0°C
30
28
26
24
22
20
18
16
27
ASHRAE Recommended
Supply Air Temperature of CRAH Unit: 15.00°C
Mean Air Inlet Temperature of IT Servers: 20.08°C
DT = 5.08
HAC
C-1 C-2 C-3 C-4 C-5 C-6 C-7 C-8 C-9 C-10 C-11 C-12 C-13 C-14 C-15 C-16 C-17 C-18 C-19 C-20
Hot-Aisle Containment (HAC) Measurement Points (in Cold Aisles [C])
B.
30
28
26
24
22
20
18
16
Test Case 2: Cold-Aisle Containment (CAC) with Supply Air Temperature of 15.0°C
27
Mean Air Inlet Temperature of IT Servers: 22.50°C
ASHRAE Recommended
Supply Air Temperature of CRAH Unit: 15.00°C
DT = 7.50
18
CAC
C-1 C-2 C-3 C-4 C-5 C-6 C-7 C-8 C-9 C-10 C-11 C-12 C-13 C-14 C-15 C-16 C-17 C-18 C-19 C-20
Cold-Aisle Containment (CAC) Measurement Points (in Cold Aisles [C])
C.
30
28
26
24
22
20
18
16
Test Case 3: Hot-Aisle Containment (HAC) with Supply Air Temperature of 17.0°C
27
ASHRAE Recommended
Mean Air Inlet Temperature of IT Servers: 22.10°C
DT = 5.10
18
Supply Air Temperature of CRAH Unit: 17.00°C
HAC
C-1 C-2 C-3 C-4 C-5 C-6 C-7 C-8 C-9 C-10 C-11 C-12 C-13 C-14 C-15 C-16 C-17 C-18 C-19 C-20
Hot-Aisle Containment (HAC) Measurement Points (in Cold Aisles [C])
Test Case 3: HAC with SA 17.0°C (63°F)
For the HAC system, the variations of the IT environment
were analyzed while changing the supply air temperature
of the CRAH units. As shown in Figure 7c and
Figure 8c, when the supply air temperature of the CRAH
units was 17.0°C (63°F), the mean air inlet temperature
of IT servers in the cold aisle (C-1 to C-20 in Figure 7c) was
22.1°C (71.8°F).
Approximately 5.1°C (9.2°F) was lost in the supply
airstream. This is similar to the loss in the supply air
54
ASHRAE JOURNAL ashrae.org A U G UST 2021
temperature of 15.0°C (59°F) and was approximately
2.4°C (4.3°F) lower than the CAC's 15.0°C (59°F).
The inlet air temperature of each IT server was within
the ASHRAE recommended range; however, hot spots
(C-17 and 19 in Figure 7c) occurred. The average outlet air
temperature of rack servers in the hot aisle after IT heat
removal (H-1 to H-10 in Figure 8c) was 29.4°C (84.9°F).
The ΔT of inlet and outlet air was 7.3°C. Nevertheless,
the fact that the hot aisle's average air temperature was
lower than the return air temperature implies that the
recirculation occurred in many areas.
18
A.
Rack Inlet Temperature (°C)
Rack Inlet Temperature (°C)
Rack Inlet Temperature (°C)
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
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