ASHRAE Journal - July 2021 - 15

TECHNICAL FEATURE
spaces can play a vital role in determining
the risk of infection.2,3
The effectiveness of ventilation
depends on several factors related
to the design and operation of HVAC
systems, which can impact the airfl ow
patterns in indoor spaces. Ideally,
the clean supply air should sweep
the contaminants from the breathing
zone without signifi cant recirculation
and stagnation that usually
form pockets of high concentration.
Similarly, the clean air should not
escape or short-circuit the space
FIGURE 1 Office CFD models for the two HVAC configurations (location and number of supply diffusers and return
grilles ) analyzed in this study.
Supply
Infected Person
Partitions
Supply (TYP 2)
Infected Person
Return
(TYP 2)
Return
Case 1: Single Supply and Single Return
without collecting and removing contaminants from the
breathing zone.
The path of least resistance that the air often follows
is generally not intuitive. Airfl ow patterns, the resulting
fl ow path of airborne contaminants and the risk of
infection can depend on several factors including the
number, location and type of supply diffusers in the
space; supply airfl ow rates (air change rates) and associated
diffuser throws; supply air temperature; number,
size and locations of return/exhaust grilles; the location
and strengths of various heat sources in a room; an
arrangement of furniture and other obstructions to airfl
ow; location, type and capacity of in-room air cleaners;
and, importantly, the relative positions of contaminant
sources in a space. Strategic layout of supply diffusers
and exhaust grilles can form the airfl ow patterns that
can help reduce the risk of contaminant exposure in
indoor spaces.2,3
Physical testing and real-time measurements of all the
parameters that affect the ventilation performance of
enclosed spaces are often time- and labor-intensive, if
not impossible. In such situations, CFD analyses provide
a feasible alternative to gain comprehensive insights
into the ventilation performance. Insights into complex
airfl ow patterns and the fl ow path of airborne contaminants
gained during the early stages of a design or
retrofi t process can help improve the ventilation performance
and reduce the risk of infection in indoor spaces.
Virtual Offi ce Space
A comparative analysis was performed of the ventilation
effectiveness of two different HVAC layouts
for a typical offi ce space with two cubicles.
Case 2: Distributed Supply and Distributed Return
Three-dimensional, steady-state, isothermal CFD models
were developed for this study. The space has an about
300 ft2 (27.9 m2) area with 9 ft (2.74 m) height with a total
occupancy of six persons. As shown in Figure 1, the two
cubicles are separated by a 5 ft (1.5 m) tall dividing partition.
Each cubicle has an about 100 ft2 (9.3 m2) area. A
common corridor is adjacent to these cubicles leading to
the room's door. Each cubicle has three occupants seated
around a table.
Figure 1 shows an infected individual facing two other
individuals located in a cubicle farthest from the door.
The offi ce space is designed for the supply airfl ow fl ow
rate of 135 cfm (63.7 L/s) or 3 air changes per hour
(ach, h-1), which corresponds to the total cooling load
of 3,000 Btu/h (879 W) for a 20°F (11.1°C) difference
between the supply and return air temperature.
Two CFD models are developed for two different HVAC
confi gurations. Figure 1 shows that the Case 1 model has
a single four-way ceiling supply diffuser located away
from the door with a single return grille placed near the
door. In the Case 2 model, an additional four-way ceiling
diffuser and return grille are added. To distribute
the supply air evenly to all occupants, the diffusers are
placed over each cubicle. Similarly, to create sweeping
airfl ow through the occupied zone, the return grilles are
placed away from the occupants in the adjacent corridor,
and the supply diffusers are moved closer to the opposite
wall. Thus, the Case 2 model forms a symmetric layout
of distributed supply and distributed return in the
space. The total supply airfl ow rate of 135 cfm (63.7 L/s)
is equally divided between the two diffusers.
The k-epsilon turbulence model was used to compute
the turbulent viscosity of the air. A computational mesh
J U LY 2 0 2 1 ashrae.org ASHRAE JOURNAL
15
http://www.ashrae.org

ASHRAE Journal - July 2021

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

Contents
ASHRAE Journal - July 2021 - Intro
ASHRAE Journal - July 2021 - Cover1
ASHRAE Journal - July 2021 - Cover2
ASHRAE Journal - July 2021 - 1
ASHRAE Journal - July 2021 - Contents
ASHRAE Journal - July 2021 - 3
ASHRAE Journal - July 2021 - 4
ASHRAE Journal - July 2021 - 5
ASHRAE Journal - July 2021 - 6
ASHRAE Journal - July 2021 - 7
ASHRAE Journal - July 2021 - 8
ASHRAE Journal - July 2021 - 9
ASHRAE Journal - July 2021 - 10
ASHRAE Journal - July 2021 - 11
ASHRAE Journal - July 2021 - 12
ASHRAE Journal - July 2021 - 13
ASHRAE Journal - July 2021 - 14
ASHRAE Journal - July 2021 - 15
ASHRAE Journal - July 2021 - 16
ASHRAE Journal - July 2021 - 17
ASHRAE Journal - July 2021 - 18
ASHRAE Journal - July 2021 - 19
ASHRAE Journal - July 2021 - 20
ASHRAE Journal - July 2021 - 21
ASHRAE Journal - July 2021 - 22
ASHRAE Journal - July 2021 - 23
ASHRAE Journal - July 2021 - 24
ASHRAE Journal - July 2021 - 25
ASHRAE Journal - July 2021 - 26
ASHRAE Journal - July 2021 - 27
ASHRAE Journal - July 2021 - 28
ASHRAE Journal - July 2021 - 29
ASHRAE Journal - July 2021 - 30
ASHRAE Journal - July 2021 - 31
ASHRAE Journal - July 2021 - 32
ASHRAE Journal - July 2021 - 33
ASHRAE Journal - July 2021 - 34
ASHRAE Journal - July 2021 - 35
ASHRAE Journal - July 2021 - 36
ASHRAE Journal - July 2021 - 37
ASHRAE Journal - July 2021 - 38
ASHRAE Journal - July 2021 - 39
ASHRAE Journal - July 2021 - 40
ASHRAE Journal - July 2021 - 41
ASHRAE Journal - July 2021 - 42
ASHRAE Journal - July 2021 - 43
ASHRAE Journal - July 2021 - 44
ASHRAE Journal - July 2021 - 45
ASHRAE Journal - July 2021 - 46
ASHRAE Journal - July 2021 - 47
ASHRAE Journal - July 2021 - 48
ASHRAE Journal - July 2021 - 49
ASHRAE Journal - July 2021 - 50
ASHRAE Journal - July 2021 - 51
ASHRAE Journal - July 2021 - 52
ASHRAE Journal - July 2021 - 53
ASHRAE Journal - July 2021 - 54
ASHRAE Journal - July 2021 - 55
ASHRAE Journal - July 2021 - 56
ASHRAE Journal - July 2021 - 57
ASHRAE Journal - July 2021 - 58
ASHRAE Journal - July 2021 - 59
ASHRAE Journal - July 2021 - 60
ASHRAE Journal - July 2021 - 61
ASHRAE Journal - July 2021 - 62
ASHRAE Journal - July 2021 - 63
ASHRAE Journal - July 2021 - 64
ASHRAE Journal - July 2021 - 65
ASHRAE Journal - July 2021 - 66
ASHRAE Journal - July 2021 - 67
ASHRAE Journal - July 2021 - 68
ASHRAE Journal - July 2021 - 69
ASHRAE Journal - July 2021 - 70
ASHRAE Journal - July 2021 - 71
ASHRAE Journal - July 2021 - 72
ASHRAE Journal - July 2021 - 73
ASHRAE Journal - July 2021 - 74
ASHRAE Journal - July 2021 - 75
ASHRAE Journal - July 2021 - 76
ASHRAE Journal - July 2021 - 77
ASHRAE Journal - July 2021 - 78
ASHRAE Journal - July 2021 - 79
ASHRAE Journal - July 2021 - 80
ASHRAE Journal - July 2021 - 81
ASHRAE Journal - July 2021 - 82
ASHRAE Journal - July 2021 - 83
ASHRAE Journal - July 2021 - 84
ASHRAE Journal - July 2021 - 85
ASHRAE Journal - July 2021 - 86
ASHRAE Journal - July 2021 - 87
ASHRAE Journal - July 2021 - 88
ASHRAE Journal - July 2021 - 89
ASHRAE Journal - July 2021 - 90
ASHRAE Journal - July 2021 - 91
ASHRAE Journal - July 2021 - 92
ASHRAE Journal - July 2021 - 93
ASHRAE Journal - July 2021 - 94
ASHRAE Journal - July 2021 - 95
ASHRAE Journal - July 2021 - 96
ASHRAE Journal - July 2021 - 97
ASHRAE Journal - July 2021 - 98
ASHRAE Journal - July 2021 - 99
ASHRAE Journal - July 2021 - 100
ASHRAE Journal - July 2021 - 101
ASHRAE Journal - July 2021 - 102
ASHRAE Journal - July 2021 - 103
ASHRAE Journal - July 2021 - 104
ASHRAE Journal - July 2021 - 105
ASHRAE Journal - July 2021 - 106
ASHRAE Journal - July 2021 - 107
ASHRAE Journal - July 2021 - 108
ASHRAE Journal - July 2021 - 109
ASHRAE Journal - July 2021 - 110
ASHRAE Journal - July 2021 - 111
ASHRAE Journal - July 2021 - 112
ASHRAE Journal - July 2021 - Cover3
ASHRAE Journal - July 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