The first semester (Design + Research) project
Introduction
Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method
This paper aims to investigate thermal sensation inside KAU classrooms by studying air temperature and air velocity and adapting these two variables as necessary along with adopting different ventelation strategies to improve thermal sensation inside the classrooms . This paper should provide guidelines to optimize thermal sensation inside classrooms in presence of a new plans to raise the targeted teacher to student ratio from 1:17 to 1:45 in high density areas
7. Methodology of the study
7. Methodology of the study Classroom Classroom AA plan
Classroom ClassroomBB plan
Fig. 25 : Air temperature vs air velocity for class B seatings
Fig. 24 : Air temperature vs air velocity for class A seatings
26.00
1. Research objective
0.35
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0.30 25.00
Improving thermal sensation inside KAU classrooms by testing other ventilation types and controlling air temperature / air velocity without making major changes in the existing buildings and with minimum technical complexity .
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23.50
21.00-22.00 C° 22.01-23.00 C° 23.01-26.00 C°
0.08
0.04
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7. Methodology of the study 9
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Air temperature reference point
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Mean air velocity
20 10
Variables
Classroom A
Classroom B
Classroom Area Classroom volume Meshing method Mesh sizing Nodes Elements Gravitational acceleration Turbulence model Inlet velocity Inlet temperature Number of occupants Human body heat generation rate Other heat sources Heat Transfer Coefficient of walls Wall thickness Number of inlets Number of outlets
69 m² 204.75 m³ Tetrahedrons Fine, medium and coarse Varies Varies 9.81 m/s2 K-epsilon (k-ε) 2 m/s 22 °C 60 55 W/m2 No 1.1 W/(m2K) 0.2 m 3 3
46 m² 141.28 m³ Tetrahedrons Fine, medium and coarse Varies Varies 9.81 m/s2 K-epsilon (k-ε) 2 m/s 21 °C 45 55 W/m2 No 1.1 W/(m2K) 0.2 m 2 2
2
3
4
5
6
7
8
9
17
25
35
44
14
24
34
43
13
23
33
42
12
22
32
41
11
21
31
40
10
20
30
39
19
29
21.00-22.00 C° 22.01-23.00 C° 23.01-26.00 C°
19 20
21
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23 24
25
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27 28
29
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31 32
33
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37
38
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Air temperature reference point
Mean air Temperature
Air velocity reference point
Mean air velocity
7. Methodology of the study CFD simulation Grid Independence Test Classroom A plan
Coarse
27
Medium
Fine
10
Classroom B plan
Measurment values Point No. Temp °C 1 22.75 2 22.6 3 22.65 4 22.7 5 22.81 6 22.97 7 23.01 8 23.05 9 22.71 10 22.7
Fine mesh size Temp °C 22.74 22.67 22.69 22.73 22.74 22.73 22.71 22.66 22.70 22.78
Relative error % Temp 0.06 0.33 0.18 0.15 0.32 1.04 1.31 1.68 0.05 0.34
Mediun mesh size Temp °C 22.76 22.76 22.74 22.71 22.74 22.76 22.75 22.77 22.76 22.69
Relative error % Temp 0.03 0.71 0.38 0.03 0.30 0.91 1.12 1.23 0.22 0.03
C oarse mesh size Temp °C 22.96 22.86 22.81 22.72 23.10 23.08 22.98 23.01 22.64 22.81
Relative error % Temp 0.92 1.14 0.70 0.10 1.26 0.48 0.15 0.18 0.29 0.48
Measurment values Point No. Temp °C 1 21.69 2 21.65 3 21.57 4 21.85 5 21.9 6 21.93 7 21.9 8 21.9 9 21.96 10 22
Fine mesh size Temp °C 21.81 21.65 21.58 21.65 21.77 21.92 22.12 22.32 22.51 22.01
Relative error % Temp 0.56 0.01 0.06 0.93 0.60 0.02 1.00 1.94 2.50 0.05
Mediun mesh size Temp °C 21.75 21.69 21.69 21.77 21.93 22.04 22.10 22.14 22.15 22.15
Relative error % Temp 0.26 0.21 0.56 0.35 0.12 0.51 0.92 1.09 0.86 0.68
C oarse mesh size Temp °C 21.88 21.61 21.87 22.04 21.95 22.34 22.15 22.45 22.50 22.05
Relative error % Temp 0.89 0.17 1.38 0.87 0.25 1.87 1.13 2.52 2.48 0.23
Averag 22.80 Maximum 23.05
22.71 22.78
0.55 1.68
22.74 22.77
0.50 1.23
22.90 23.10
0.57 1.26
Averag 21.84 Maximum 22.00
21.94 22.51
0.77 2.50
21.94 22.15
0.56 1.09
22.09 22.50
1.18 2.52
Table 14 : Grid independent test on Classroom B, Supply air temperature = 22 °C, Supply air velocity = 2 m/s
Usually 5 % relative error is acceptable in such cases (13. Ernest Z., 2014) Nodes = 2121 Elements = 9130
Nodes = 11905 Elements = 58431
Supply air temperature = 22 C°, Supply air velocity = 2 m/s
Nodes = 53423 Elements = 280999
Classroom B
1
2
3
4
5
6
7
8
9
10
Supply air temperature = 22 C°, Supply air velocity = 2 m/s
23.15 23.10 23.05 23.00 22.95 22.90 22.85 22.80 22.75 22.70 22.65 22.60
22.60 22.40 22.20 22.00 21.80 21.60
0
1
2
3
4
5
6
7
8
9
10
21.40
11
0
1
2
3
4
Seat No. Fine mesh size
Nodes = 56448 Elements = 300385
Nodes = 12078 Elements = 59912
Nodes = 1993 Elements = 8863
8. FFD simulation of the current conditions 7.3 CFD simulation
8.1 Classroom A 7.3.1 CFD simulation of of status quo
Coarse mesh size
Fine mesh size
8
9
10
11
Medium mesh size
Coarse mesh size
Fig. 22 : Three mesh sizes comparison for classroom B status quo
Air temperature distribution
Air temperature C°
Air velocity m/s
Compatibility with ASHRAE 55
Air temperature distribution
Air velocity distribution
comfort zone
comfort zone
Detecting best and worst places
7
CFD simulation
Fig. 27 : CFD simulation for Classroom A's status quo
7.3.1.1 CFD simulation of the current status of Classroom A
6
7. Methodology of the study 1
9.3.2 CFD simulation of the current conditions of Classroom A
Medium mesh size
5 Seat No.
Fig. 21 : Three mesh sizes comparison for classroom A status quo
1
7. Methodology of the study
Measurement Phase 1
18
Table 13 : Grid independent test on Classroom A, Supply air temperature = 22 °C, Supply air velocity = 2 m/s
Before starting the simulation grid independent test carried out to verify the CFD grid density first
Hot and Dry
University
Analysing results
15
Inlet location
Classroom A
1
15 16
Supply air temperature = 22 C° , Supply air velocity = 2 m/s
Data Collection
45
Air velocity reference point
Mesh sizing configuration in Ansys
Classroom and reference points
14
ASHRAE 55 recommended thermal limit
CFD simulation Grid Independence Test
CFD Simulation Framework
4. Methodology 7. Methodology of the studyof the study
Selection of the study sample
36
Seat No.
Inlet location
7. Grid Independence Test
13
Air Temperature C°
Number of articles
Mean air Temperature
10
0.00
7.3 CFD simulation of 7.the current Methodology of the study situation
30
Secondary
26
0.00
20.00
Air Temperature C°
1
ASHRAE 55 recommended thermal limit
40
Primary
16
20.50
0.05
50
Mediterranean
37
0.02
21.00
60
Tropical and Subtropical
27
21.00
70
Temperate
17
Cool Slight Cool Comfort zone
21.50
0.10
80
0
38
0.06
22.00
Figure below shows Type of documents on Scopus scientific database when search with keywords “thermal comfort, adaptive thermal comfort and thermal comfort in classroom” (ac- cessed on 11th October 2018).
Adaptive thermal comfort articles
28
Air temperature 22.00
26
1,090
1
18
22.50
0.15
3. Identifying a research gap
Database
Air Velocity m/s
Cool Slight Cool Comfort zone
23.00
Seat No.
Scopus
2
0.10 Air Temperature C°
Air Velocity m/s
Air Temperature C°
23.00
20.00
Thermal comfort articles
4
0.12
24.00
Air temperature
0.20
Comfort zone
18,888
6
0.14
3
What is the optimum configuration of mechanical air supply diffusers in classrooms that help avoid draft sensation under certain conditions ?
Classroom comfort articles
7
25.00
24.00
Slight Cool
2. Research question
8
0.16
Cool
395
0.18
26.00
Measurement Phase 2
Displacement ventilation system
CFD simulation
1 7.3.1 CFD simulation of of status quo
1 Air temperature distribution
Fig. 27 : CFD simulation for Classroom B's status quo
7.3.1.2 CFD simulation of the current status of Classroom B
Air temperature C°
Air velocity m/s
Stratum ventilation system (DV)
Classroom
1.07 0.88 1.95
7.50
Air conditioning system Number of ceiling diffusers Type of ceiling diffusers
classrooms± ( are in 0.4% + shown 1 C° ) the following figures.
1.07
ected -50.1 - 100 C°
Number of sitting places Number of windows Number of doors Door type 1.27
Table. 11 Details of the experimental equipment
The following figures shows the the Bsellected 4 ( Class A readings ) and plans 15-18 (ofClass readngs ) classrooms indicat-
B
7.5 Classroom9.1A plan 3 204.75 69 Metal panels Granite tiles Smooth paint White
1.11
Width [m] Length [m] Ceiling height [m] Volume [m³] Floor area [m²] Ceiling material Floor material Surface walls material Surface color
0.1 C°
lues of air temperature and air velocity is much closer to the Classroom A plan in table 8 in general as it appears in Fig. 19 . mperature values in a little bit above than the average in the Fig. 8 REED Thermo-Anemometer model SD-4214 ys of the room, These values slightly increas at the Southern 17 one adjasent to the window. While air velocity values are he m/s ) ge in class corners except the one opposite to the door where r significantly in that section in addition to the central part ) it5 C°apppears in Fig. 19. ) tC°different in Class B, where both air velocity and air tempermor up or down the average than Class A. As Figs. 15-18 of air velocity values is 0.105 m/s ( 61.76 % ) lower than the ncattable 8), while the average of air temperature readings is Classroom B plan bove from table as it appears 7. Methodology of the8, study the the mean of air temperature
A
9.14
1
60 2 1 Double Swing Door
45 3 1 Double Swing Door
5.93
PMV = -1.32
7.4 Proposed scena
93% below 25 m/s
Return
1 Return
Supply
Return Supply
Supply
Supply
Supply
2. Displacement ventilation (DV)
3. Stratum ventilation (SV)
Raising supply air temperature to 24 °C and velocity to 2 m/s
Raising supply air temperature to 24 °C and velocity to 2 m/s
7. Methodology of the study
Scenario 1 (MV 1)
CFD Simulation Framework Variables
Classroom A
Classroom B
Classroom Area Classroom volume Meshing method Mesh sizing Nodes Elements Gravitational acceleration Turbulence model Inlet velocity Inlet temperature Number of occupants Human body heat generation rate Other heat sources Heat Transfer Coefficient of walls Wall thickness Number of inlets Number of outlets
69 m² 204.75 m³ Tetrahedrons Medium 11905 58431 9.81 m/s2 K-epsilon (k-ε) 2 m/s 24 °C 60 55 W/m2 No 1.1 W/(m2K) 0.2 m 3 3
46 m² 141.28 m³ Tetrahedrons Medium 12078 59912 9.81 m/s2 K-epsilon (k-ε) 2 m/s 24 °C 45 55 W/m2 No 1.1 W/(m2K) 0.2 m 2 2
CFD simulation
Mixing ventilation (MV)
9.1 Scenario 1 : Mixing ventilation (MV 1)
Classroom A in Scenario 1.1
Classroom B in Scenario 1.1
Classroom A in Scenario 1.1
Air temperature
Air temperature
Compatibility with ASHRAE 55
Air velocity
Air velocity
Classroom B in Scenario 1.1 PMV = -0.52
Compatibility with ASHRAE 55
PMV = -0.47
1.07
7.79
1.95
7.50
0.88
1.07
1.69
Supply air temperature = 22 C° , Supply air velocity = 2 m/s
7.4.2 CFD simulation of proposed scenarios
In s study carried out by Fong, M. L., Vic Hanby, Rick Greenough, Z. Lin, and Y. Cheng (12. Fong et al. 2015) in Hong Kong to investigate the acceptability of thermal conditions under three different ventilation strategies : Mixing ventilation (MV), Displacement ventilation (DV) and stratum ventilation (SV), the first strategy (MV) is the most conventional air distribtion method as the supply air is pumped into the occupied zone using fans and mix completelly with the existing air before making any contact with 1. Mixing ventilation (MV) the occupants, It is common in this strstegy to use the vertical supply from the ceiling to avoid any obstacles such as partitioning walls. The second ventilation strategy in the displacement ventilation (DV) in which supply air is driven at a Raising supply air temperature to 24 °C and low level and rech the occupants before becoming warmer and thus lighter and extracted from the velocity to 2 m/s ceiling. Jackman (13.P.J. Jackman, 1990 ) recommend using lower air velocities - less than 0.25 m/s - in case 1.1 Retain ceiling 1.2 Changing ceiling of displacement ventilation to avoid disrupting comfort of occupants . diffusers configuration diffusers configuration The third ventilation 7. Methodology of the studymode is the stratum ventilation (SV) where air supply horizontally using diffusers 1 7.4 CFD simulation mounted at head or chest level on the walls of a room . Fong and his colleagues concluded the the stratum ventilation strategy (SV) can provide mor ofsatis7. Methodology the study CFD simulation factory thermal conditions for the occupants even at elevated temperature up to 27.1-27.9 °C .
Senario 1
1.06
North direction
1.11
96% below 23 °C
Supply air temperature = 22 C° , Supply air velocity = 2 m/s
Supply
Central AC 4 Square diffusers
Table. of the investigated classrooms1.24 0.60 10 Characteristics 1.24 1.79
1
9. CFD simulation of proposed scenarios
Central AC 6 Square diffusers
Classroom B plan
7. Methodology of th
7.4 CFD simulation
5.9 7.8 3.07 141.28 46 Metal panels Granite tiles Smooth paint White
9.14
Air velocity distribution
7. Methodology of the study
1.69
Two classrooms in building 535 7.3 Objective measurements 7.3.1 Measurement Phase 1 on the preparatory year faculty Field test parameters included airwere temperature and air velocity. sellected, The choice of the Air temperature and air velocity were measured at thedue heighttoof the 1.1 m avaliabilfrom the classrooms floor in each measurment point within the classrooms as shown in Fig. 7 . ity of the students and teachers The measurment process took a place between 1 and 4 PM when classrooms in during the day; Furthermore, the Range Resolutions theParameters preparatory year are almost full of students in October 9thAccuracy 2019 . two atclassrooms different Measurment process lasted 10 minutes each measurmenthave point with time 0.2 - 5.0 m/s 0.01 m/s area, number of ±students, sample of 1 minute . Air velocity ( 1% + 0.1 m/s ) win5.1 used - 25.0inm/s 0.1 surfaces m/s is REED and Measurement equipment the experiment Thermo-Anemometer dows orientation in model SD-4214 as shown in Fig. 9order . to have a significant samTable 11 shows details -50 of the experimental used . ± ( 0.4%of+ 0.5 C° ) sell- 1300 C°ples . equipment some pictures the
comfort zone
ogy of the study 5. Selection of study sample
Compatibility with ASHRAE 55
Air temperature distribution
comfort zone
16
Supply air temperature = 22 C° , Supply air velocity = 2 m/s
comfort zone
7. Methodology of the study
Air temperature
Supply air temperature = 22 C° , Supply air velocity = 2 m/s
comfort zone
Determining the ideal scenario
90% below 25 m/s
CFD simulation
7. Methodology of the study
8.2 Classroom B
CFD simulation for Proposed solving scenarios
PMV = -1.14
7. Methodology of the study
7. Methodology of the study 7.3 CFD simulation
Evaluating scenarios based on thermal comfort parameters and energy consumption
81% below 23 °C
comfort zone
Mixing ventilation system (MV)
comfort zone
CFD simulation for current status
the hern are here part
1.79
Classroom A
1.24
Senario 1
7. Methodology of the study
1.06
Classroom B plan
North direction
1.24
1.79
1.24
1.07 7.79 0.88
Section A 5
1.95
Classroom A in Scenario 1.1
Air temperature
Air temperature
Compatibility with ASHRAE 55
Air velocity
Air velocity
Classroom B in Scenario 1.1 PMV = -0.54
Compatibility with ASHRAE 55
PMV = -0.16
Air temperature distribution
Air velocity distribution
Air temperature distribution
Air velocity distribution
Section B 2
7.4 CFD simulation
Section B 1
Section A 6
Senario 2
7. Methodology of the study
7. Methodology of the study
CFD simulation Scenario 2 (DV)
Classroom B
CFD simulation
1
9.3 Scenario 2 : Displacement Displacement ventilationventilation (DV) (DV)
1 Classroom A in Scenario 2
Classroom B in Scenario 2
Classroom A in Scenario 1.1
Air temperature
Air temperature
Compatibility with ASHRAE 55
Classroom B in Scenario 1.1 PMV = -0.13
Compatibility with ASHRAE 55
PMV = -0.15
1.27
1.07
7.79
Section A 4
Classroom B in Scenario 1.1
7. Methodology of the study
Classroom A
Section A 2
Classroom A in Scenario 1.2
1.06
1.69
1.11
1
5.93
7.50
Section A 3
CFD simulation
1
1.75
Fig. 6 Plans of the selected classrooms 0.60
7. Methodology of the study
CFD simulation Scenario 1.1 (MV 2)
Classroom B
9.2 Scenario 1.1 : Mixing ventilation (MV 2) Mixing ventilation (MV)
9.14
per5-18 the gs is ears
Air velocity distribution
7.4 CFD simulation
Classroom A plan
Section A 1
Air temperature distribution
7. Methodology of the study
1.27
6. Data collection 1.24
Air velocity distribution
Comfort zone
5.93
0.60
Air temperature distribution
Section B 3
7. Methodology of the studyMeasurement point Section boundary
Section B 4
1.75
North direction
Fig. 6 Plans of the selected classrooms
Air velocity
Air temperature distribution
Air velocity
Air velocity distribution
Air temperature distribution
Air velocity distribution
1.75
Fig. 9 Air velocity vs air temperature in section A1 23.85
0.2
23.5 23.4
0.15
23.3
0.1
23.2 23.1
0
1
2
3
4
5
6
7
8
9
10
11
0.25
23.65
0.2
23.6 23.55
0.15
23.5
0.1
23.35
Air velocity
4
6
7
8
9
10
Fig. 12 Air velocity vs air temperature in section A4 0.35
23.65
0.2
23.6 23.55
0.15
23.5
0.1
23.45 23.4 4
5
6
7
8
9
10
11
Air temperature °C
0.25
3
23.9
0.2
23.8 0.15 23.7 0.1
23.6
0.05
23.5
0
23.4
0 0
1
2
3
4
5
6
7
8
9
10
Classroom A
11
Air temperature Air velocity Fig. 9 Air velocity and air temperature measurements in section A1 Average air velocity : 0.044 Average air temperature : 24.91
Series2
Average air velocity : 0.172
Average air temperature : 23.74
23.50
23.74
23.56
23.36
0.04
0.11 0.03
23.33 0.08
23.00
0.02
0.04
1
0.10 0.05
0
2
1 3
4
2
5
3
6
7 Class section
4 8
9
5
10
11
0.00 7
60
24.00
22.00 0
1
2
0 10
: 24.02
11
24 23.9
24.00
0.05
24.31
24.020.04
23.98 0.12
0.03
23.50
4
5
6
23.7
0.02
0.07
23.00 22.50
23.6 23.5
0
22.00 1
0.03
0.03
0.01 0
0
2
3
4
1
5
6
2
Time ( in minutes )
7
8
Standard air velocity : 0.17
0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00 5
3
9
10
4
Air temperature
22
11
24.50
24.39
24.00
24.31 24.02
23.98 0.12
23.50
0.07
23.00 22.50
0.03
0.03
3
4
22.00
0
1
2
Class section
Air velocity
Average air temperature
Average air velocity : 0.07 Average air temperature : 24.18 Average air velocity : 0.034 Average air temperature : 24.02 Standard deviation : 0.04 Standard deviation : 0.21 Standard air velocity : 0.17
CFD simulation 10.1 Final results Evaluating scenarios
Status quo
MV 1 scenario
MV 2 scenario
DV scenario
SV scenario
PMV value = -1.14
PMV value = -0.52
PMV value = -0.54
PMV value = -0.13
Compatibility with ASHRAE 55
PMV = -0.14
Standard air temperature : 23.00
Air velocity distribution
Air temperature distribution
Air velocity distribution
10.2 Conclusion
Classroom A
1.5
Classroom B
PMV value = -0.10
Average air temperature = 22.57 °C Average air temperature = 25.21 °C Average air temperature = 25.21 °C Average air temperature = 25.30 °C Average air temperature = 25.32 °C Average air velocity = 0.15 m/s Average air velocity = 0.25 m/s Average air velocity = 0.26 m/s Average air velocity = 0.11 m/s Average air velocity = 0.11 m/s Complies with ASHRAE 55 : No Complies with ASHRAE 55 : No Complies with ASHRAE 55 : No Complies with ASHRAE 55 : Yes Complies with ASHRAE 55 : Yes
PMV value = -1.32
PMV value = -0.47
PMV value = -0.16
PMV value = -0.15
PMV value = -0.14
Average air temperature = 21.91 °C Average air temperature = 25.21 °C Average air temperature = 25.39 °C Average air temperature = 25.25 °C Average air temperature = 25.28 °C Average air velocity = 0.10 m/s Average air velocity = 0.23 m/s Average air velocity = 0.15 m/s Average air velocity = 0.12 m/s Average air velocity = 0.12 m/s Complies with ASHRAE 55 : No Complies with ASHRAE 55 : Yes Complies with ASHRAE 55 : Yes Complies with ASHRAE 55 : Yes Complies with ASHRAE 55 : Yes
Test conditions : 1. Operative temperature = Varies as above, 2. Air speed = Varies as above, 3. Relative humidity = recommended value ( 40-60%), 4. Metabolic rate = 1 met (sitting quietly condition), Clothing level = 0.57 clo ( Trousers, short-sleeve shirt, socks, shoes and underwear ) 1
Standard air temperature : 23.00
25.00
Class section
Average air velocity
PMV = -0.10
1
1
Classroom B
0.00 7
Average air temperature : 23.89 Standard deviation : 0.65
The Department of Architecture (KAUARCH) Faculty of Architecture and Planning King Abdulaziz University 23.8
0.10
Average air temperature
Average air velocity : 0.14 Standard deviation : 0.07
Air velocity m/s
24.1
24.39
3
Average air velocity
Air temperature °C
0.01
24.50
24.2
Air temperature °C
0.02
Air temperature °C
0.03
Air velocity m/s
0.04
0.06
Air temperature distribution
0.5
Fig. 20 Average air temperature and velocity in class B sections
Air velocity m/s
24.3
0.05
Air velocity
Status Quo 0
A
B
-0.5
MV1 A
-0.52
Class section
Standard air temperature : 23.00
25.00
24.4
0.06
Air velocity
MV2 B
A
0.05
0.04
and velocity in class Fig.Fig. 1820 AirAverage velocityairvstemperature air temperature in section B4 B sections
on B4
0.11
23.33 0.08
23.00
Average air temperature
Standard air velocity : 0.17
0.15
23.74
23.56
23.36
Air temperature Air velocity Average air velocity : 0.14 Average air temperature : 23.89 : Average 0.07 air temperature Standard deviation Average airStandard velocity :deviation 0.03 : 24.31 : 0.65
24.31
24.45
0.17
23.50
Classroom
0.20
24.50
Time ( in minutes ) Average air velocity
0.22
24.91
0.21
22.50
0.01
22.00 0
0.15
0.25
25.00
0.20
0.05 24.45
0.17
24.00
Compatibility with ASHRAE 55
7. Methodology of the study
Fig. 34 : Comparing scenarios based on PMV values according to ASHRAE Standard 55-2017
Air velocity m/s
24.50
22.50
24.15
11
24.91
0.21
0.06
10. Results and discussion
Classroom A
Average air velocity
Average air velocity : 0.07 Standard deviation : 0.04
Standard air velocity : 0.17
Average air temperature
Average air temperature : 24.18 Standard deviation : 0.21 Standard air temperature : 23.00
0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00 5
Air velocity m/s
0
0.22
25.50
Air temperature °C
24.25 24.2
0.01 10
24.3
0.25
0.07
Air velocity m/s
0.02
24.35
Air temperature °C
0.03
Air temperature °C
0.04
24.4
Air velocity m/s
0.05
25.50 25.00
Air temperature
1
CFD simulation Evaluating scenarios
Series1
Fig. 19 Average air temperature and velocity in class A sections
Air velocity m/s
0.06
Air temperature
Classroom B in Scenario 1.1
Classroom B
7. Methodology of the study
Time ( in minutes )
Fig.Fig. 1719 AirAverage velocityairvstemperature air temperature in section B3 A sections and velocity in class 24.45
Classroom A in Scenario 1.1
0.05
These results contradict the questionnaire carried out at the beggining of this study what can be interpreted that the selected measurment points might not be enough to repre7. Methodology of the study sent the entire community of the classrooms precisely.So, more points will be tested in measurment phase 2 . 0.07
Classroom B in Scenario 1.1
0.25
Time ( in minutes )
on B3
Classroom A in Scenario 1.2
0.3
24
Air velocity m/s
23.7
2
1
11
24.1
0.3
20
5
Fig. 10 Air velocity vs air temperature in section A2
23.75
Air temperature °C
3
Average air temperature : 23.32
23.8
1
2
Air temperature Air velocity Average air velocity : 0.215 Average air temperature : 23.56
23.85
0
Stratum 9.4 Scenario 3 : Stratum ventilation (SV)ventilation (DV) (SV)
CFD simulation
Time ( in minutes )
Air temperature
23.35
1
7. Methodology of the study
CFD simulation Scenario 3 (SV) 1
Classroom B
0 0
Time ( in minutes )
Average air velocity : 0.211
Senario 3
0.05
23.4
0
Classroom A
7. Methodology of the study
Air velocity m/s
22.9
23.7
23.45
0.05
23
0.3
23.75
Air temperature °C
23.6
7.4 CFD simulation
0.35
23.8
0.25
Air velocity m/s
Air temperature °C
23.7
Fig. 7 Division of the classrooms and measurement points
Air velocity m/s
0.3
23.8
19
7. Methodology of the study
Fig. 11 Air velocity vs air temperature in section A3
-1 -1.14
-1.5
-1.32
Omar Hussein Al-hebshi Supervisor: Dr-Ing. Mohannad Bayoumi
-0.47
-0.54
DV
SV
B
A
B
A
B
-0.16
-0.13
-0.15
-0.10
-0.14
1. The distribution of air temperature and air velocity varies in different places within the classrooms, while the best places include the middle section and the front one adjacent to the window, the worst sections generally are the ones at the back of the classroom opposite to the windows, where air temperature and air velocity are much further from the comfort limits . 2. The current conditions of the classrooms don’t fit within ASHRAE 55’s comfort zone, whereas air temperature is lower than 23 °C in most cases ( it should be between 23-26 °C to match ASHRAE 55 ), air velocities tend to be lowe than 0.25 m/s usually which seems good . 3. Testing different ventilation methods with reducing supply air temperature to 22 °C and retaining supply air velcity at 2 m/s showed that the currently installed displacement ventilation method don’t give the recommended PMV value by ASHRAE 55, although the PMV value of this mehod can be enhanced by using linear ceiling diffucers as tested in scenario 1.1 . The two best ventilation strategies in the two classrooms are the strstum and displacement ventilation in order, as both resulted in more consistence distribution of air temperature and air velocity in addition to PMV values which are more close to neutral condition .