Numerical investigations of the indoor thermal environment in atria and of the buoyancy-driven ventilation in a simple atrium building

1. Queen’s University
Kingston
Dr. Shafqat Hussain
1

2.  An atrium is usually defined as a large and tall glazed space in a multi-storey building.
 Highly glazed atria are currently incorporated into the design of many large modern
buildings in order to take advantage of daylighting, solar heating and buoyancy-driven
natural ventilation.
 Indoor thermal environment of an atrium building involves many complex features, such
as forced, mixed and natural convection and complex radiation-convection interactions.
 Estimation of thermal and energy performance of an atrium building is difficult because of
the complex thermal phenomena involved.
 Not enough experimental and numerical data on the thermal phenomena in atria is
available
 Use of Computational Fluid Dynamics (CFD) techniques in the study of indoor
environment and thermal comfort conditions in atria buildings.
2

3.  Evaluate the performance of various turbulence models and a
radiation model for the prediction of indoor environment in the
atrium of the Engineering building of Concordia University, Montreal
for which experimental data is available.
 Study the indoor environment numerically in the atrium of the
building located in Ottawa for which experimental data is available
in literature.
 Validate the accuracy of CFD predictions of the thermal
phenomena in atria considered against the experimental
measurements .
 Evaluate the thermal comfort conditions in the atrium of the
Concordia building for the occupants under hybrid ventilation
conditions.
3

4.  Study the buoyancy-driven ventilation numerically in a simple
atrium building.
 Study the effect of the thermal mass of the outer envelope on the
transient thermal performance of the building.
 Investigate the effect of design changes in the atrium space on the
buoyancy-driven ventilation and temperature distribution in the
building.
 Study the selected geometry of the atrium building to examine the
sensitivity of its ventilation performance to different geometric and
climatic parameters.
 Examine the use of buoyancy-driven night ventilation in the atrium
building and evaluate the thermal comfort conditions for the
occupants.
4

5.  The experimental measurements were recorded in part of an atrium (14-
16 floors) in the Engineering building at Concordia University by Mouriki
(2009).
 In this study the numerical simulations were undertaken by solving the
Reynolds Averaged Navier-Stokes (RANS) and energy equations for
steady and three-dimensional turbulent flow using the commercial CFD
solver FLUENT.
 The numerical results were obtained using six turbulence models with
the radiation model, DTRM under forced ventilation conditions and
compared with the experimental results.
1) K-Epsilon-standard.
2) K-Epsilon-RNG
3) K-Epsilon-realizable.
4) K-Omega-STD
5) K-Omega-SST.
6) Spalart-Allmaras
5

6. Geometrical Model
 The simulations were run using a
somewhat simplified model of the
atrium interior.
(12.05 m x 9.39 m x 13.02 m)
Total volume = 1345m3
 South facing wall is façade
glazing surface.
 East wall is with air supply and
return
 The area of the supply, return and
the floor plan are shown
6

7. The average air temperature distribution along the height of the atrium at
16:00hr on 1st
August 2007
Average Air Temeratures vs Height of the Atrium
16
18
20
22
24
26
28
30
32
0 1 2 3 4 5 6 7 8 9 10 11 12
Height (m)
Temperature(oC)
EXP
SKE
RNGKE
RKE
SKW
SSTKW
SA
7
 Percentage error between predictions and measurements is relatively higher (4 to 10%) for the Spallart-
Allamaras turbulence model and lower (0.1 to 5%) for the k-ω-SST turbulence model.

8.  Effect of solar intensity on the air temperature
distribution within the atrium.
Mean air temperature distribution at three levels of
the atrium space using four turbulence models from
13:00 to 16:00 hrs.
Average air temperatures at high level of the atrium
16
18
20
22
24
26
28
30
32
13:00 14:00 15:00 16:00
Time (hr)
Temperature(
o
C)
Measured
SST-k-omega
STD-k-epsilon
RNG-k-epsilon
Realizable-k-epsilon
Average air temperatures at middle level of the atrium
16
18
20
22
24
26
28
30
13:00 14:00 15:00 16:00
Time (hr)
Temperature(oC)
Measured
SST-k-omega
STD-k-epsilon
RNG-kepsilon
Realizable-k-epsilon
Average air temperature at low level of the atrium
16
18
20
22
24
26
28
13:00 14:00 15:00 16:00
Time (hr)
Temperature(o
C)
Measured
SST-k-omega
STD-k-epsilon
RNG-kepsilon
Realizable-k-epsilon
 Overall SST-k-omega turbulence model performed
relatively better than the k-epsilon models.
8

9.  An atrium space of a building located in Ottawa was selected for
numerical study using a CFD approach for which the experimental and
computed results were available in literature .
 Numerical results were obtained using three turbulence models under
forced ventilation conditions.
1) K-Epsilon-standard
2) K-Epsilon-RNG
3) K-Omega-SST
 Numerical results were compared with the experimental and computed
results (ESP-r) obtained by Abdelaziz et al (1999)
9

10.  The atrium has an octagonal shape with a pyramidal skylight
enclosed in a three-storey building and has open corridors at each
storey connecting it to adjacent spaces.
10

11. The atrium simulatedThermocouple locations for air temperature
measurements (Abdelaziz-1999)
SupplySupply
ReturnReturn
Glass surfaces
11

12. Comparison of measured and CFD predicted values of average temperatures
obtained using three turbulence models at three floors of the atrium space at
12:00 pm on June, 1995.
12
18
20
22
24
26
28
First Second Third
Floors
Temperature(C)
Abdelaziz(1999),measured
k-ε-STD-predicted
k-ε-RNG-predicted
k-ω-SST-predicted

13. Comparison of measured, computed (ESP-r) and CFD predicted values of average
temperatures at three floors of the atrium space (10-11 June, 1995)
13

14. 10-11 June, 1995 9 -10 December, 1995
14

15. Numerically predicted temperature distribution in the atrium10-11 June, 1995Numerically predicted temperature distribution in the atrium10-11 June, 1995Numerically predicted temperature distribution in the atrium10-11 June, 1995Numerically predicted temperature distribution in the atrium10-11 June, 1995Numerically predicted temperature distribution in the atrium10-11 June, 1995
Comparison of measured, computed and CFD predicted values of average
temperatures at three floors of the atrium space (9 -10 December, 1995)
15
 From the results it is seen that the CFD model predicted the temperature values mostly better than the
computed values obtained by Abdulaziz and Atif (1999) using ESP-r code

16. 16
Cases
Date/Time
(16:00h)
Outdoor Air
Temperature (°C)
Solar Radiation
(W/m³)
Natural
Ventilation
Mechanical Air
Blinds
Temp. (°C) Flow Rate
(m3
/s)
Case-A Sep 23rd
, 2007 20 250 ON 17 0.20 Closed
Case-B Sep 1st
, 2007 20 205 ON 17 0.12 Open
Case-C July 25th
, 2007 26 130-180 OFF 14 1.60 Closed
Case-D Nov 2nd
, 2007 6 280 OFF 14 1.20 Open
Dimensions (m) and Areas(m2)
Atrium Height 13.02 Façade Glass Area 97.00 Floor Grills(net) Area 1.97
Atrium Width 9.39 Façade Blind Area 82.00 Corridor grills(net) Area 1.40
Atrium Depth 12.05 Air Supply (net) rea 0.40 Air Exhaust(net) Area 5.40
Air Return(net)
Area
7.44
Dimensions and Areas of the Atrium
 Hybrid ventilation can be described as a two-mode ventilation
system using both buoyancy-driven ventilation and mechanical cooling
systems. The balance between the two systems varies with time of the
day or season.
Indoor and outdoor conditions on typical clear days, Mouriki (2009)
Floor Grills
Air supply
Air Return

17. Room Air Temperature Profiles-Blinds Closed-Natural Ventilation
ON (23/9/2007
18
20
22
24
26
28
30
32
34
36
0 2 4 6 8 10 12
Height (m)
Temperature(oC)
Measured
k-w-SST
k-e-STD
k-e-RNG
k-e-Relizable
17
Case-A
Average Air Temperature Profiles-Blinds Open-Natural Ventilation ON
(01/09/2007)
18
20
22
24
26
28
30
32
34
36
0 2 4 6 8 10 12
Height (m)
Temperature(oC)
Measured
k-w-SST
k-e-STD
k-e.RNG
k-e-Realiz
Case-B
Air temperature profiles in the atrium space on typical days with the blinds open or fully
closed and with the natural ventilation system ON.

18. Average Air Temperature Profiles-Blinds Closed-Natural Ventilation OFF
(25/07/2007)
18
20
22
24
26
28
30
32
34
36
0 2 4 6 8 10 12
Height (m)
Temperature(oC)
Measured
k-w-STD
k-e-STD
k-e-RNG
k-e-Relizable
Average Air temperature Profiles-Blinds Open-Natural Ventilation OFF
(02/11/2007)l
18
20
22
24
26
28
30
32
34
36
0 2 4 6 8 10 12
Height (m)
Temperature(oC)
Measured
k-w-SST
k-e-STD
k-e-RNG
k-e-Realiz
18
Case-C Case-D
Air temperature profiles in the atrium space on typical days with the blinds open or fully
closed and with the natural ventilation system OFF.
 It is seen that the numerical predictions obtained are generally in acceptable agreement with the
experimental measurements. The average difference between the predicted and measured air
temperatures is in the range of 1 to 8%

19. Case-A: Natural ventilation ON and blinds closed.(Sep 23rd
,2007)Case-A: Natural ventilation ON and blinds closed.(Sep 23rd
,2007)Case-A: Natural ventilation ON and blinds closed.(Sep 23rd
,2007)Case-A: Natural ventilation ON and blinds closed.(Sep 23rd
,2007)
Z
(m)
Case-A Case-B
x =1m x =3 x =5 x =1 x =3 x =5
PMV PPD PMV PPD PMV PPD PMV PPD PMV PPD PMV PPD
1 -0.46 9.5 -0.47 9.6 -0.54 11.2 -0.51 10.4 -0.51 10.5 -0.49 10.1
3 -0.49 10.1 -0.49 10.0 -0.51 10.5 -0.55 11.2 -0.52 10.8 -0.51 10.5
5 -0.41 8.5 -0.56 11.7 -0.61 12.9 -0.48 9.8 -0.51 10.4 -0.57 11.7
7 -0.41 8.6 -0.48 9.9 -0.55 11.4 -0.60 12.6 -0.53 11.0 -0.48 9.9
Z
(m)
Case-C Case-D
x =1m x =3 x =5 x =1 x =3 x =5
PMV PPD PMV PPD PMV PPD PMV PPD PMV PPD PMV PPD
1 -1.27 38.7 -1.1 30.7 -1.02 26.8 1.00 26.0 0.80 18.6 0.96 24.6
3 -1.17 33.9 -0.71 15.6 -0.66 14.2 0.99 25.9 0.95 24.1 0.94 23.7
5 -1.27 38.6 -0.89 21.6 -0.74 16.6 1.06 28.8 0.72 16.0 0.85 20.3
7 -1.03 27.6 -0.76 17.1 -0.86 20.4 0.98 25.3 1.04 27.7 1.1 30.6Calculated values of the PMV and PPD indices at various x and z coordinates at a height of 1.1m above atrium floor for
different cases considered. PMV = [0.0303exp(-0.036M)+0.028]L PPD =100-95exp[-0.03(PMV)4-0.22(PMV)2] 19
 Thermal comfort is defined in ISO 7730 as "the condition of mind that expresses satisfaction with the thermal
environment“
 The PMV and PPD are calculated from six basic variables: activity, clothing, air temperature, air velocity, mean radiant
temperature (MRT), and relative humidity (%).
 Dissatisfaction with the thermal environment, discomfort was defined by participants using the 7- point scale: cool (–2), cold (–
3), warm (+2) or hot (+3). Under optimal thermal conditions (PMV = 0) 5% of persons will be dissatisfied

20. Case B
Case A
Case C Case D
Prediction of percentage
dissatisfied (PD(%))
contours at a height of
1.1 m in the occupied
area of the atrium for the
four cases considered.
20
Draft is described as any
localized feeling of
coolness or warmth of
any portion of the body
due to air movement, air
temperature and
turbulence intensity and
is expressed in terms of
PD (%)

21. 21
Table 5-3 Volume flow rates at three floors using three mesh densities
Façade glazing wall
Atrium
Inlets
Outlets
Dimensions and Areas of the Atrium Building
Dimensions and Areas
Atrium height 16.00m
Atrium width 5.00m
Atrium depth 6.00m
Room height 4.00m
Room width 6.00m
Room depth 6.00m
Façade glazing area 80.00m2
Ground floor air supply (net) area 0.80m2
First floor air supply (net) area 1.00m2
Second floor air supply (net) area 1.60m2
Atrium outlet opening (net) area 3.40m2
Simple Atrium Building

22. 22
Sun Direction Vector
x y z
-0.54 0.84 -0.06
Sunshine Fraction 1
Direct Normal Solar Irradiation (at Earth's surface) [W/m2
] 863
Diffuse Solar Irradiation - vertical surface [W/m2
] 232
Diffuse Solar Irradiation - horizontal surface [W/m2
] 109
Ground reflected solar irradiation-vertical surface[W/m2
] 91.05
Outside Heat Transfer Coefficient [W/m2
-o
C] 7.4
Outside Air Temperature [o
C] 25
Solar irradiation and outside conditions in Montreal at 13:00 on July 15, 2010

23. 23
Inlet opening area on
each floor
(m2
)
Total effective
opening area
(At / H2
)
Volume flow rate (m3/s) Air changes per hour (ACH)
Left-hand side rooms Left-hand side rooms
Ground
floor
First floor Second
floor
Groun
d floor
First
floor
Secon
d floor
0.2 0.0087 0.27 0.22 0.17 7 5 4
0.4 0.017 0.44 0.34 0.25 11 8 6
0.6 0.026 0.59 0.42 0.32 15 11 8
0.8 0.035 0.75 0.65 0.45 19 16 11
1 0.044 0.85 0.66 0.45 21 16 11
Floors
Inlet opening
area
(m2
)
Total effective
opening area
(At / H2
)
Volume flow rate
(m3
/s)
Air changes per hour
(ACH)
Left side Right side Left side Right side
Ground floor 0.40 0.0170 0.42 0.42 12 12
First floor 0.50 0.0235 0.42 0.42 12 12
Second floor 0.80 0.0380 0.40 0.41 11 12
Volume flow rates (m3
/s) and air changes per hour (ACH) with different inlet opening area
on each floor of the building (Holford and Hunt (2003))
Variation in the volume flow rate of the buoyancy-driven ventilation in the left-hand side
rooms of the building with the increase of inlet opening area in each storey for outside
conditions in Montreal at 13:00 on July 15, 2010.

24. Comparison between the CFD model predictions and the analytical model predictions (Holford and Hunt
(2003)) for the non-dimensional volume flow rate having the same total effective opening area Ajt
for each
floor of the building (a) and having different total effective opening area Ajt
for each floor of the building (b)
to have same flow rate on each storey.
24
(a) (b)
0
0.2
0.4
0.6
0.8
1
1.2
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045
At/H
2
Non-dimensionalvolumeflowrate
Analytical-ground floor
CFD-ground floor
Analytical-first floor
CFD-first floor
Analytical-second floor
CFD-second floor
0
0.2
0.4
0.6
0.8
1
0 0.01 0.02 0.03 0.04
Non-dimensional Total Effective Area (At/H
2
)
Non-dimensionalVolumeFlowRate
Analytical-ground floor
Analytical-first floor
Analytical-second floor
CFD-ground floor
CFD-first floor
CFD-second floor
+
Q (h) = c (Bh5
)1/3
(Morton et al (1956))

25. 0.2
0.25
0.3
0.35
0.4
0.45
0.5
ST
John
M
ontreal
W
innipeg
Calgary
Vancouver
ST
John
M
ontreal
W
innipeg
Calgary
Vancouver
M
ontreal
W
innipeg
Calgary
Vancouver
Volumeflowrate(m3
/s)
Ground floor
First floor
Second floor
Effect of geographical location of the building on the volume flow rate with the same ventilation
rate in each storey at 13:00hr on 15April, 15July and 15 September 2010 in different cities of
Canada (St John, Montreal, Winnipeg, Calgary and Vancouver).
25

26. Ground floor
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00
Time (h)
Volumeflowrate(m
3
)
internally insulated walls)
externally insulated walls
walls without insulation
First floor
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00
Time (h)
Volumeflowrate(m
3
/s)
Internally insulated walls
Externally insulated walls
Walls without insulation
Second floor
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00
Time (h)
Volumeflowrate(m
3/
s)
Internally insulated walls
Externally insulated walls
Walls without insulation
Comparison of the variation in volume flow rates for the three cases considered in each storey.
26
External walls
20cm thick
made of
concrete
blocks with
and without
insulation
covering

27. Basic design changes in the geometry of atrium of a simplle atrium building
27
Case-A
Case-B
Case-C
Case-D
Case-E
Case-F

28. 28
Buoyancy-driven natural ventilation volume flow rate in each storey and temperature (o
C) values
in the centre of each room on the left-hand side of the building.
Atrium
designs
Glazing
area
(m2
)
Volume flow rate (m3
/s)
in each room
Temperature (o
C) at 1.1 m from floor of each
room
Ground
floor
First floor Second
floor
Atrium
inlet
Ground
floor
First floor Second
floor
Atrium
inlet
Case-A 80 0.37 0.37 0.35 0.72 32.62 32.36 31.87 32.62
Case-B 154 0.44 0.45 0.42 0.83 33.64 33.43 32.97 33.79
Case-C 127 0.43 0.42 0.40 0.78 33.56 33.48 33.05 33.65
Case-D 90 0.42 0.42 0.39 0.81 33.32 33.09 32.70 33.32
Case-E 94 0.42 0.42 0.40 0.80 33.61 32.39 32.68 33.93
Case-F 286 0.51 0.52 0.49 1.00 35.28 34.79 35.65 34.79

29. 29
PPD (%) values for seated persons in the centre of
each room
4
6
8
10
12
14
16
Ground floor First floor Second floor Atrium floor
PPD(%)values
Atrium width 4m
Atrium width 5m
Atrium width 6m
PPD (%) values for seated persons in the centre of
each room
4
6
8
10
12
14
16
Ground floor First floor Second floor Atrium floor
PPD(%)values
Atrium depth 6m
Atrium depth 8m
Atrium depth 10m
PPD (%) values for seated persons in the centre of
each room
4
6
8
10
12
14
16
18
Ground floor First floor Second floor Atrium floor
PPD(%)values
Chimney width 1m
Chimney width 2m
Chimney width 3m
PPD (%) values for seated persons in the centre of
each room
4
6
8
10
12
14
16
Ground floor First floor Second floor Atrium floor
PPD(%)values
Chimney height 2m
Chimney height 4m
Chimney height 6m
PPD (%) values for seated persons in the centre of
each room
4
6
8
10
12
14
16
Ground floor First floor Second floor Atrium floor
PPD(%)values
Inlets above floor 0m
Inlets above floor 0.6m
Inlets above floor 1.2m
Effect of the various geometric parameters for seated activity in the centre of each occupied
floor of the building.
Case-E

30. 30
PPD (%) values for seated persons in the centre of
each room
4
6
8
10
12
14
16
18
Ground floor First floor Second floor Atrium floor
PPD(%)values
Glazing area 68 m2
Glazing area 107 m2
Glazing area 118 m2
PPD (%) values for seated persons in the centre of each
room
4
6
8
10
12
14
16
18
Ground floor First floor Second floor Atrium floor
PPD(%)values
At 7:00 hr
At 13:00 hrs
At 18:00hrs
PPD (%) values for seated persons at the centre of
each room
4
6
8
10
12
14
16
18
20
Ground floor First floor Second floor Atrium floor
PPD(%)values
Blinds open Blind half open Blinds closed
PPD values for seated persons in centre of each room
4
6
8
10
12
14
16
18
Ground floor First floor Second floor Atrium floor
PPD(%)values
Emisivity 0.4
Emissivity 0.8
Emissivity 1.0
PPD (%) values for seated persons in the centre of
each room
4
6
8
10
12
14
16
18
Ground floor First floor Second floor Atrium floor
PPD(%)values
Transmissivity 0.16
Transmissivity 0.36
Transmissivity 0.56
PPD (%) values for seated persons in the centre of
each room
4
6
8
10
12
14
16
Ground floor First floor Second floor Atrium floor
PPD(%)
Absorptivity 0.075
Absorptivity 0.175
Absorptivity 0.375
Figure 6.6 a,b Effect of the solar intensity (a) shading (b) on PPD (%) values for seated activity in the centre of each occupied floor of the building.Figure 6.6 a,b Effect of the solar intensity (a) shading (b) on PPD (%) values for seated activity in the centre of each occupied floor of the building.Figure 6.6 a,b Effect of the solar intensity (a) shading (b) on PPD (%) values for seated activity in the centre of each occupied floor of the building.
Effect of the various climatic parameters for seated activity in the centre of each occupied floor of the
building.

31. 31
Modified design of the atrium building
Dimensions and areas of the atrium building selected
Dimensions and Areas
Atrium Height 12.00m
Atrium Width 5.00m
Atrium Depth 6.00m
Exhaust chimney width 2.00m
Exhaust chimney height 6.00m
Height of inlets from ground and first floor 1.1m
Room Height 4.00m
Room Width 6.00m
Room Depth 6.00m
Façade Glazing Area 60.00m2
Ground Floor air supply (net) area 1.20m2
First Floor air supply (net) area 1.08 m2
second Floor air supply (net) area 1.80 m2
Atrium outlet opening (net) area 4.08m2

32. Geographical
Locations
Volume flow rate (m3/s) at each airflow inlet
LHS Rooms RHS Rooms Atrium
Ground
floor
First
floor
Second
floor
Ground
floor
First
floor
Second
floor
St. John 0.46 0.47 0.46 0.46 0.47 0.46 0.85
Montreal 0.46 0.45 0.47 0.46 0.47 0.46 0.87
Calgary 0.45 0.45 0.46 0.45 0.46 0.47 0.85
Table 6-10 Ventilation volume flow rate at each inlet of the floors in four cities
Glazing
surface face
Volume flow rate (m3
/s) at each airflow inlet
LHS Rooms RHS Rooms Atrium
Ground floor First
floor
Second
floor
Ground
floor
First
floor
Second
floor
South-West 0.44 0.43 0.48 0.44 0.44 0.51 0.81
South 0.47 0.46 0.49 0.48 0.46 0.51 0.86
South-East 0.45 0.45 0.46 0.45 0.46 0.47 0.85
Ventilation volume flow rate at each inlet of the floors for various
orientations of the building
Ventilation volume flow rate at each inlet of the floors in four cities at a3:00 hr
on July 15, 2010
32
at 13:00hr on July15, 2010at 13:00hr on July15, 2010

33. Z
(m)
Ground Floor First Floor
X=1m X=3 X=5 X =1 X=3 X=5
PMV PPD PMV PPD PMV PPD PMV PPD PMV PPD PMV PPD
1 -0.45 8.4 -0.44 9.2 -0.56 11 -0.46 9.5 -0.56 11 -0.60 12.7
3 -0.27 6.7 -0.60 16.2 -0.54 10.8 -0.39 8.1 -0.48 10.2 -0.52 10.4
5 -0.48 9.7 -0.44 9.2 -0.53 10.6 -0.50 10.3 -0.54 10.8 -0.58 11.2
Z
(m)
Second Floor Atrium Floor
X=1m X=3 X=5 X =1 X=3 X=5
PMV PPD PMV PPD PMV PPD PMV PPD PMV PPD PMV PPD
1 -0.73 15.9 -0.77 16.4 -0.79 18.4 -0.23 6.3 -0.18 5.4 -0.25 6.3
3 -0.70 16.4 -0.76 16.3 -0.83 19.3 -0.18 5.4 -0.58 11.2 -0.24 6.2
5 -0.73 15.9 -0.77 16.4 -0.79 18.4 -0.38 8.0 -0.50 10.2 -0.34 7.8
Calculated values of PMV and PPD at 0.6m above floors in the atrium building
33

34. PD contours at the horizontal plane 1.1m from each floor of the building.PD contours at the horizontal plane 1.1m from each floor of the building.
PD contours at the horizontal plane 0.6m above each floor of the
building for seated activity.
34

35. 35
Case-A: Night ventilation induced by the heat sources present on each floor of the building.
Case-B: Night ventilation induced by hot water at 80o
C flowing in the chimney walls and in
central plate, both being 3m high in the chimney.
Case-C: Night ventilation induced by both heat sources on each floor and plus hot water at
80o
C of the chimney walls and central plate.
Case-D: Night ventilation induced by both heat sources on each floor and plus hot water at
60o
C of the chimney walls and central plate.
Case-E: Night ventilation induced by both heat sources on each floor and plus hot water at
40o
C of the chimney walls and central plate.
Case-F: Night ventilation induced by heat sources on each floor and by hot water at 80o
C
flowing in the chimney walls, i.e., without the central heated plate .

36. 36
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Case-A Case-B Case-C Case-D Case-E Case-F
Volumeflowrate(m3/s)
Ground floor
First floor
Second floor
Comparison of the volume flow rates (m3
/s) in the right-hand side
rooms for the different cases of night ventilation considered.

37. Z
(m)
Ground Floor First Floor
X=1m X=3 X=5 X =1 X=3 X=5
PMV PPD PMV PPD PMV PPD PMV PPD PMV PPD PMV PPD
1 -0.32 7.7 -0.32 7.7 -0.28 6.7 -0.28 6.7 -0.35 7.6 -0.34 7.4
3 -0.50 15.20 -0.36 8.1 -0.35 7.9 -0.40 6.2 -0.34 7.4 -0.35 7.6
5 -0.32 7.7 -0.41 8.2 -0.23 5.8 -0.30 7.4 -0.34 7.4 -0.34 7.4
Z
(m)
Second Floor Atrium Floor
X=1m X=3 X=5 X =1 X=3 X=5
PMV PPD PMV PPD PMV PPD PMV PPD PMV PPD PMV PPD
1 -0.37 7.9 -0.37 7.9 -0.37 7.9 -0.36 7.7 -0.40 8.4 -0.41 8.6
3 -0.37 7.9 -0.37 7.9 -0.37 7.9 -0.36 7.7 -0.30 7.4 -0.35 7.4
5 -0.37 7.9 -0.37 7.9 -0.39 8.2 -0.35 7.4 -0.39 8.2 -0.37 7.9
Calculated values of PMV and PPD at 0.6m above each floor in the atrium
building for seated activity
37

38. 38
PD contours along the horizontal planes at the height of 0.6 m above
each floor in the building considered

39. •All of the turbulence models considered gave results that agreed well with the experimental results
to an accuracy that can be used in, at least, the preliminary design of atria.
•The performance of the two-equations turbulence models was better than the one-equation
turbulence model. Taken overall, the best agreement between the experimental and numerical results
was obtained when using the SST-k-ω turbulence model.
•Calculated PMV, PPD and PD values under hybrid ventilation conditions in the occupied area of the
Concordia atrium showed that thermal comfort conditions are satisfactory and only a relatively small
percentage of less than 12% of the occupants is expected to be slightly uncomfortable.
•Using the SST-k-ω turbulence model and DTRM radiation model demonstrate the ability of the
validated CFD model to predict the three-dimensional buoyancy-driven ventilation flows in a simple
three-storey atrium building.
•Design curves developed by Holford and Hunt (2003) are useful in establishing the sizes of air inlet
and outlet vents to achieve equal ventilation flow rates in each storey of the atrium building.
• Favorable agreement was achieved between simple analytical models calculations and CFD
predictions of the non-dimensional volume flow rates in a simple atrium building.
39

40.  In the building envelope with heavy thermal mass and outside insulation covering, some amount of
heat is stored in the walls that could be beneficial to control the inside temperature fluctuations and for
night-time ventilation in the absence of the solar irradiation.
 From the analysis of the effect of design changes, it was found that the atrium space integrated with
a chimney on the roof is more suitable option to develop buoyancy-driven ventilation air flow rate in the
building.
 From the results of the parametric study , the values of the geometric parameters and glazing
properties were determined for the design specifications of the atrium space integrated with a chimney
in an atrium building.
 Thermal conditions developed in the building as a result of the use of buoyancy-driven ventilation
were neutral comfortable on the ground floor, the first floor, and the atrium floor while on the second
floor they were slightly cool acceptable.
 Buoyancy-driven night ventilation would provide acceptable comfort conditions inside the atrium
building, which can be maintained by exhausting relief air from the building through the atrium and night
cooling with ambient air.
 CFD methods can be applied successfully as design tool to model the indoor thermal environment in
atria buildings.
40