METHODS TO IMPROVE INDOOR ENVIRONMENTAL QUALITY (IEQ) IN CLASSROOMS IN HOT CLIMATES. 02

Improving thermal sensa�on in classrooms with respect to dra� avoidance by op�mizing the mechanical air supply method Omar Husein Al-hebshi Supervisor: Dr-Ing. Mohannad Bayoumi

AR 600 Advanced Studio Department of Architecture Faculty of Architecture and Planning King Abdulaziz University

First Semester 2019/2020

Contents 01. Introduc�on 02. Research Framework 03. Point of departure 04. Research problem 05. Research objec�ve 06. Research ques�on 07. Research hypothesis 08. Literature review 09. Methodology 10. Results and discussion 11. Conclusion 12. Acknowledgments 13. References

1 2 3 4 5 6 7 8 9 10

1. INTRODUCTION Young students spend approximately 30% of their lives in school classrooms 1. (Giuli, Da, & Carli, 2012)

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

Keywords : Thermal sensation CFD simulation Subtropical climates Classrooms Ventilation strategies Comfort zone

3

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

2. FRAMEWORK

Fanger Comfort Equation

Breathing

The main factors that influence THERMAL COMFORT

M-W = (C+R+Esk) +(Cres+Eres) 1. Metabolic Rate 2. Clothing Insulation

Skin Natural Ventilation

3. Air Temperature

Testing Several Ventilation Strat-

4. Air Velocity 5. Air Humidity

Artificial Ventilation

M = Metabolic rate W = Work C = Heat transfer by convection from clothing surface R = Heat transfer by radiation fromclothing surface Esk = Evaporative convective heat exchange Cres = Respiratory evaporative heat exchange Eres = Respiratory evaporative heat exchange L = Thermal load on the body L = Internal heat production - Heat loss to the actual environment L = M - W - [(Csk + Rsk + Esk) + (Cres+Eres)] PMV = (0.303 exp (-0.036 M) + 0.028 ) x L

6. Radiant Temperature

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

4

2. Research Problem 3. Point of departure

4. Research problem

examine thermal sensation of the students in King Abdulaziz 2.Touniversity, Research problem Google form based question was published in variety of

Results of the questioner in of Fig.uncomfortable 1 illustrates thatthermal 17.13 and 33.30 % of the This paper investigate the issue sensation caused by have air draft generated by the mechanical students cold and cool and sensations respectively . ventilation Many students in system KIng insideAbdulaziz som of King Abdulaziz university classrooms .

University and other educational institutions reported

social media groups of KAU students, 75 students participated in the questionnaire.

To examine thermal sensation of the students in King Abdulaziz university, Google form based contains question was published in varietyasking of social groupstoof The questionier only one question themedia students evaluate their sensation in inside the classroom by choosing KAU students, 75 thermal students participated the questionnaire one of the PMV scale’s values : cold, cool, cool, The questionier contains only one question askingslightly the students toneutral, evaluate their slightly warm, warm and hot, questionieer results are shown in Fig. thermal sensation inside the classroom by choosing one of the PMV scale's 1 as following values : cold, cool, slightly cool, neutral, slightly warm, warm and hot, questionieer results are shown in Fig. 1 %33.30

%35.00

No. of participants

%20.00

%18.60

%10.00

What is the optimum configuration of mechanical air supply diffusers in class-

%1.33

%0.00 slightly cool

Improving thermal sensation inside KAU classrooms by testing other ventilation 6. Research question

7. Research hypothesis rooms that help avoid draft sensation under certain conditions ?

%6.66

%5.00 cool

3. Research objective

4. Research question

%15.00

cold

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 .

What is the optimum configuration of mechanical air supply diffusers in classrooms that help avoid draft sensation under certain conditions ?

%22.60 %17.30

student ratio from 1:17 to 1:45 in some high density areas .

types and controlling air temperature / air velocity without making major changes in the existing buildings and with minimum technical complexity .

%30.00 %25.00

complaint about inadequate indoor air quality and thermal conditions inside the

5. Research objective classrooms. This conditions can be worsen with a new plans to raise teacher to

neutral

slightly warm

warm

PMV value

%0 hot

Air supply locations as well as air supply temperature play an important role in creating and avoiding draft sensation .

5. Research hypothesis

Air supply locations as well as air supply temperature play an important role in creating and avoiding draft sensation .

Fig. 1 Results of the implemented questionnaire to evaluate students' thermal sensation

2 5

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

d as “prima-

as “second-

8.2 Identifying a research gap

In a study carried out by Kumar, M., Ooka, R., Rijal, H. B., Kumar, S., & Kumar in 2019 (Kumar et al. 2019), The authors invesigated the progress in thermal comfort studies in classrooms over the last 50 years in different parts of the world to gives detail insight of the thermal comfort studies done in classrooms across the world and analyze the results.

8.2.1 Number of studies done about classrooms’ thermal comfort

The research articles are classified into three categories: 1. Kindergarten, elementary and primary school classrooms, referred as “primary school classroom” for analysis.

2. Secondary, senior secondary and high school classrooms, referred as “secondary school classroom” for analysis.

3. University classroom

6. Literature review

Figure below shows Type of documents on Scopus scientific data6.2 Identifying a research gap base when search with keywords “thermal comfort, adaptive thermal comfort and thermal comfort in classroom” (ac- cessed on 11th October 2018).

18,888

Thermal comfort articles

6.2.1 Number of studies done about classrooms’ thermal comfort Fig. 2 shows Type of documents on Scopus scientific database when search with 395 keywords comfort “thermalarticles comfort, adaptive thermal comfort and thermal comfort in Classroom Database classroom” (ac- cessed on 11th October 2018).

Scopus

1,090

Adaptive thermal comfort articles

To carry out this study Scopus database is searched with keyword “thermal comfort study in classrooms”. Total 93 research articles appeared

152

M.K. Singh, R. Ooka and H.B. Rijal et al. / Energy & Buildings 188–189 (2019) 149–174

M.K. Singh, R. Ooka and H.B. Rijal et al. / Energy & Buildings 188–189 (2019) 149–174

12000

12

10000

Number of documents publishes

14

10 8 6 4

Thermal comfort

Adaptive thermal comfort

165

Thermal comfort in classrooms

No. of Classroom comfort articles : 395 No. of Adaptive thermal comfort articles : 1090 No. of Thermal comfort articles : 395

8000 6000 4000 2000

Year

Re p Bu sin ort ess art icle

l

tte r Le

ito r ia

Ed

No te

Bo ok Sh ort sur vey Er r atu m

Re s ea r Co ch ar t nfe ren icle ce pap er Re vie w Bo ok cha pte Ar r tic le i np Co res nfe s ren ce rev iew

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

2006

2006

2004

2003

1988

1977

1975

1973

0

1972

2 1969

., & Kumar t studies in gives detail e world and

8.1 Progress in thermal comfort studies in classrooms

Number of research papers published

s over last

8. Literature review

Fig. publishedover overthetheyears years in classroom thermal comfort (accessed 11th October 2018).

Fig.1.1.Number Number of of paper paper published in classroom thermal comfort (accessed on 11thon October 2018).

Table 1 Characteristics of classrooms at different levels of education.

Fig. 7. Type of documents on Scopus scientific database when search with keywords “thermal comfort, adaptive thermal comfort and thermal comfort in classroom” (acFig. 2 Type cessed on 11th October 2018).of documents on Scopus scientific database when search with keywords “thermal comfort, adaptive thermal comfort and

Classrooms at different levels of education

thermal comfort in classroom” (ac- cessed on 11th October 2018).(4) 1. Naturally Ventilated (NV): A Classroom is constructed to operate under free aggravate the unacceptability of existing thermal environrunning (FR) condition 12 months a year and same is considered under thewhich ment [39,40,83,84].

Parameters

Kindergarten

Elementary/Primary

Secondary/Sr. Secondary

University

3-6

7-11

12-18

19-26

High

Depending on class and

Depending on class and

Depending on class and

Improving thermal sensation in classrooms with Children respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi Occupants Children Children Adults Age group (Approximately) Density

6

class. So they are in transient condition for about 20–30% of the time (if a class is of 1-hour duration). So the memory of the pre-

18).

8).

8. Literature review

Buildings 188–189 (2019) 149–174 && Buildings 188–189 (2019) 149–174

malcomfort comfort

165 165

8.2 Identifying Thermal comfortainresearch classrooms gap

canbebeseen seenininFig. Fig.44that thatthe thedistribution distributionofofstudies studiesisisquite quiteskewed. skewed.The Thehih ItItcan numberofofstudies studiesisisdone doneininsub-tropical sub-tropicalcountries countriesfollowed followedbybycountries countrie estestnumber temperateclimate. climate.Mediterranean Mediterraneanand andhot hotand anddry dryclimate climatecountries countrieshave havequq aatemperate fewstudies studiesespecially especiallyabout aboutuniversity universityclassrooms classrooms(4).

(4). aafew M.K. Singh, R. Ooka and H.B. Rijal et al. / Energy & Buildings 188–189 (2019) 149–174 M.K. Singh, R. Ooka and H.B. Rijal et al. / Energy & Buildings 188–189 (2019) 149–174

Thermal comfort in classrooms 8.2.2 Number of studies done in the classrooms of each climatic zone o.ofofClassroom Classroomcomfort comfort articles: 395 : 395 articles o.ofofAdaptive Adaptivethermal thermalcomfort comfortarticles articles: 1090 : 1090 Figs.

3 and 4 show the Koppen–Geiger world climatic classification o.ofofThermal Thermalcomfort comfortarticles articles: 395 : 395 and the number of studies done about thermal comfort in classrooms for each climatic zone.

From Figs. 3,4 and 5, we notice the following : 1. The number of reasearch articles published about thermal comfort in classrooms is very few compared to the number research articles about thermal comfort in general .

2. Among the studies done about thermal comfort in classrooms, there is almost no studies published about thermal comfort in university classroom within hot and dry zones as shown in Fig.5.

Tropical Arid Arid Temperate Temperate Tropical

keywords “thermalcomfort, comfort,adaptive adaptivethermal thermalcomfort comfortandand ywords “thermal

70 8080 60 7070 50 6060

ResearchNumber of articles studies in % Research studies in %

hot s rtusr uvrevy Er r e y Erartu atmu m No Ntoe Ed te Eidto itroia rila l Le Lteter tte Re r Rpo Bu Bsuin eprotr t sienss essar taric tilce le

rmal comfort, adaptive thermal comfort and thermal comfort classroom” (acmal comfort, adaptive thermal comfort and thermal comfort in in classroom” (ac-

163

Polar Polar

3 Worldmap mapofofKoppen–Geiger Koppen–Geigerclimate climateclassification classification(4).(4).

Fig.Fig.3 World Fig. 3. World map of Koppen–Geiger climate classification.

Fig. 3. World map of Koppen–Geiger climate classification.

80

This lack of studies about thermal comfort in university classrooms within hot and dry climatic conditions represents a research gap and needs more progress in studies to povide more information and help enhance thermal sensation in classrooms in these regions which we hope this research will help to accomplish this .

Cold Cold

163

Primary Primary Secondary Secondary University University

40 5050 30 4040 20 3030 10 2020 0 1010

ass.SoSothey theyare areinintransient transientcondition conditionfor forabout about20–30% 20–30%ofofthe the Temperate Tropical and Mediterranean Hot and Dry ss.

00 Subtropical me (if a class is of 1-hour duration).

So the memory of the preTemperate Tropical Tropical Mediterian HotHot e (if a class is of 1-hour duration). So the memory of the preTemperate && SubSub Mediterian && DryDry ious environment greatly affects the thermal comfort and preftropical Primary Secondary University us environment greatly affects the thermal comfort and prefFig. 4. Summary of thermal comforttropical studies conducted in different climates at various education level (total 89 articles).

Fig. 4. Summary of thermal comfort studies conducted in different climates at various education level (total 89 articles). rence studentininuniversity universityclassrooms. classrooms.This Thishappens happensseveral several 4 Summaryofofthermal thermalcomfort comfortstudies studiesconducted conductedinindifferent differentclimates climatesat atvarious various nce ofofa astudent Fig.Fig.4 Summary the publication followed by conference papers. It is a healthy sign 7.2. Thermal comfort and preferences in primary school classrooms mes in a day, during their stay in the university.

In classroom stueducation level (total the publication followed by conference papers.

It articles)(4). is a healthy sign 7.2. Thermal comfort and preferences in primary school classrooms es in a day, during their stay in the university. In classroom stulevel (total 8989articles)(4). because it education is enriching the database which is required to develop because it is enriching the database which is required to develop entsexperience experiencea atransient transientthermal thermalcondition conditionfor forfirst first15–20 15–20min min a robust thermal comfort model for classroom. It is also showing All 93 research articles are classified into primary, secondary nts a robust thermal comfort model for classroom. It is also showing All 93 research articles are classified into primary, secondary the increasing awareness and concern among the researchers and and university classrooms based studies. 34 out of 93 studies are the increasing awareness and concern among the researchers and and university classrooms based studies. 34 out of 93 studies are na aclass classand andwhen whenignoring ignoringthis thisfact factISO ISO7730, 7730,ASHRAE ASHRAE5555and and scientists about the IEQ and its role in the human well-being in on primary school’s classrooms. Tables 2 and 3 present the imscientists about the IEQ and its role in the human well-being in on primary school’s classrooms. Tables 2 and 3 present the imdifferent kind of built environments including classrooms. A small portant set of data related to location, time of the survey, the opEN15251 15251standard standardwhich whichgenerally generallydeals dealswith withsteady-state steady-statecondicondidifferent kind of built environments including classrooms. A small portant set of data related to location, time of the survey, the opN number of classroom centric studies are a matter of concern deeration of classrooms, sample size, comfortable temperature, neunumber of classroom centric studies are a matter of concern deeration of classrooms, sample size, comfortable temperature, neuons, applied to evaluate classrooms thermal environment, the despite knowing the impact of inadeadequate IEQ on the learning tral temperature and air velocity etc. Some rows in Tables 2 and ns, applied to evaluate classrooms thermal environment, the despite knowing the impact of inadeadequate IEQ on the learning tral temperature and air velocity etc. Some rows in Tables 2 and ability and well-being of students. It demands more studies to be 3 are highlighted showing significant information is missing in ability and well-being of students.

It demands more studies to be 3 are highlighted showing significant information is missing in 7 Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi iation reportedbybymany manystudies studiesseems seemsobvious obvious[25–27,121–124] [25–27,121–124] done across the globe so that a grand database can be built and it the published article. It may be possible that for particular study tion reported . . done across the globe so that a grand database can be built and it the published article. It may be possible that for particular study can be taken forward to the formulation of a new set of IEQ stanthose data were not necessary but for this study comfort survey erealso alsoit itisisthe thecase casewhere wherestandards standardsare areapplied appliedtotodesign designanan can be taken forward to the formulation of a new set of IEQ stanthose data were not necessary but for this study comfort survey re dards/guidelines for designing future classrooms. indicators and statistics are important to the data with a specific

(Kumar,Ooka, Ooka,Rijal, Rijal,Kumar, Kumar,&&Kumar, Kumar,2019) 2019) 4.4.(Kumar,

8. Literature review

8.3 Summaryreview 6. Literature 6. Literature review

6.3 Summary 6.3 Summary tween 1.1-1.4 met ( sedentary metabolic rate ) and temperatures According to Toftum who demonstrated that in metablic rates be-

from 22.5-23.5 °C, with air velocities less than 0.25 m/s at 1.1 m above the floor, only few occuoants complained of air draft and preffered lower air velocities, while most of occupants preffered no change at the same temperature range and air velocity range of 0 to 0.28m/s (3. Toftumm 2004) .

Table. conclude air velocity and temperature values from researches on univer-

In order to comply with ASHRAE 55, the recommended thermal limit on the 7-point scale of PMV is between -0.5 and 0.5. ISO 7730 expands on this limit, giving different indoor environments ranges.

ISO defines the hard limit as ranging between -2 and +2, for existing buildings between -0.7 and +0.7, and new buildings ranging between -0.5 and +0.5 (4. Guenther, Sebastian, 2019) .

Using both PMV and PPD indices, ASHRAE 55 dictates that thermal Cate- Thermal state of the body as a Operative temperature Max. mean air velocity oC gory whole m/s sity classrooms mentioned previously, within subtropical and hot-humid climatcomfort can be achieved based on 80% occupant satisfaction rate or more. The PPD Summer (0,5 clo) Winter(1 clo) Summer(0,5 clo) Winter(1 clo) PMV ic percentage zones because they arecan similar in climatic conditions to our based investigated remainingTable people experience dissatisfaction on from % Cooling Heating Cooling Heating belowof conclude air velocity10% and temperature values samples.

A < 6 0.2< PMV < + 0.2 25,5 – 23,5 23,0 – 21,0 0,18 0,15 whole-body discomforton (alluniversity listed influencing factors ofmentioned PMV) and 10% dissatis- within researches classrooms previously, B < 10 0.5- < PMV < + 0.5 26,0 – 23,0 24,0 – 20,0 0,22 0,18 subtropical hot-humid climatic zones because theyfewer are similar faction based on localand discomfort/partial body discomfort (includes C < 15 0.7 < PMV < + 0.7 27,0 – 22,0 25,0 – 19,0 0,25 0,21 in climatic conditions investigated samples. factors than whole-body).

In ordertotoour comply with ASHRAE 55, the recomTable. 9 Recommended levels of acceptance for operative temperature and air velocity (ISO EN 7730, 2005, CR 1752, 1998 ) (14). mended thermal limit on the 7-point scale of PMV is between -0.5 and 0.5. ISO 7730 expands on this limit, giving different indoor environments ranges. ISO Location Climate Time of survey Proposed air velocity Proposed comfort temperature defines the Researchers hard limit as ranging between -2 and +2, for existing buildings between -0.75. P.F. andHu,+0.7, andZ.N. newJiang buildingsWuhan, ranging between -0.5 and +0.5 (13) .

W. Liu, China Sub-tropical Jun to Sept and Dec to Feb 0.12 m/s 18.4-26.1 C° Zhang, C. Zhengalevels of acceptance Hunan University, China temperature Sub-tropical and Mar to Apr 2005 0.11 m/s 21.5-24.8 C° Table 9 gives6. G.recommended for operative Chongqing, China Sub-tropical Mar 2005 to May 2006 0.5 m/s 16-30 C° 7. R. Yao, J. Liu, B. Li air velocity for three classes of environment.

8. B. Cao, Y. Zhu Beijing, China Sub-tropical 9. Z. Wang, A. Li, J. Ren Harbin, China Sub-tropical Based on data tablesH. 9Ning, andX.10, we can Harbin, use temperature range from 23.5-25.5 10. Z.inWang, Zhang China Sub-tropical P. Baruah, M.K. Singh Tezpur, India as a comfort11.zone to evaluate your experimental values in the nextWarm ste and . humid 12. R. Vittal, S. Gnanasam Tamilnadu, India Warm and humid

Jun-Aug 2009; Nov-Dec 2007 Dec 2015-Jan 2015, Oct 2013 to Apr 2014 Feb and May 2013 Feb and May 2013

Average values

0.17 0.12 0.04 0.1 0.2

m/s m/s m/s m/s m/s

0.17 m/s

23-26 C° 22-25 C° 16-22.4 C° 22-23.5 C° 21.6-29.8 C°

23 C°

Table. 8 Summary and averages of air temperature and velocity values in university classrooms

15

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

13. (Guenther, Sebastian, 2019)

14. (Olesen, 2004)

8

7. Methodologyofofthe the study 9. Methodology study Measurement Phase 1 Selection of the study sample

Analysing results

Data Collection

Detecting best and worst places

Measurement Phase 2 CFD simulation for current status

Mixing ventilation system (MV)

Determining the ideal scenario

16

9

Evaluating scenarios based on thermal comfort parameters and energy consumption

Displacement ventilation system

CFD simulation for Proposed solving scenarios

Stratum ventilation system (DV)

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

9. Methodology of the study

sellected, teachers umber of t samples

7.39.1Objective measurements Selection of study sample 7.3.1 Phase TwoMeasurement classrooms in 1building 535 on the preparatory year faculty Field testsellected, parametersThe included air of temperature and air velocity. were choice the classrooms due to the avaliability of the students and teachers during the day; Furthermore, the the two Air temperature and air velocity were measured at the height of 1.1 m from classrooms have different area,the number of students, floor in each measurment point within classrooms as shown inwindows Fig. 7 . surfaces and orientation in order have a1 significant samples . some The measurment process took a placeto between and 4 PM when classrooms in pictures of the sellected classrooms are shown in Fig. 5 the preparatory year are almost full of students in October 9th 2019 .

Measurment process lasted 10 minutes at each measurment point with time Classroom sample of 1A minute .

Measurement equipment used in the experiment is REED Thermo-Anemometer model SD-4214 as shown in Fig. 9 .

Table 11 shows details of the experimental equipment used .

g system, o on are hows the Classroom B

measurdifferent

measur-

A

B

Width [m] Length [m] Ceiling height [m] Volume [m³] Floor area [m²] Ceiling material Floor material Surface walls material Surface color

7.5 9.1 3 204.75 69 Metal panels Granite tiles Smooth paint White

5.9 7.8 3.07 141.28 46 Metal panels Granite tiles Smooth paint White

Air conditioning system Number of ceiling diffusers Type of ceiling diffusers

Central AC 6 Square diffusers

Central AC 4 Square diffusers

Number of sitting places Number of windows Number of doors Door type

60 2 1 Double Swing Door

45 3 1 Double Swing Door

Table. 10 Characteristics of the investigated classrooms

on of air ded basd

gate how . 7 shows nt points

Classroom

Fig. 8 REED Thermo-Anemometer model SD-4214

17 Fig. 5 Pictures from the selected classrooms

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

10

7.79

Classroom B plan

0.60

11 1.24

1.95

0.88

5.93

1.79 1.24 1.06

1.75

North direction

17

1.69

1.11

Air conditioning system Number of ceiling diffusers Type of ceiling diffusers

Width [m] Length [m] Ceiling height [m] Volume [m³] Floor area [m²] Ceiling material Floor material Surface walls material Surface color

Classroom

9.1 Selection of study sample

7. Methodology of the study

Fig. 8 REED Thermo-Anemometer model SD-4214

1.07

9.14

7.3 Objective measurements 7.3.1 Measurement Phase 1 Field test parameters included air temperature and air velocity.

Air temperature and air velocity were measured at the height of 1.1 m from the floor in each measurment point within the classrooms as shown in Fig. 7 .

The measurment process took a place between 1 and 4 PM when classrooms in the preparatory year are almost full of students in October 9th 2019 .

Measurment process lasted 10 minutes at each measurment point with time sample of 1 minute .

Measurement equipment used in the experiment is REED Thermo-Anemometer model SD-4214 as shown in Fig. 9 .

Table 11 shows details of the experimental equipment used .

1.07

Classroom A plan

7. Methodology of the study

1.27

7.50

60 2 1 Double Swing Door

Central AC 6 Square diffusers

5 7.

3 1 4

7.5 9.1 3 204.75 69 Metal panels Granite tiles Smooth paint White

4 3 1

C 4 S

G S

B

A

Table. 10 Characteristics of the investigated classrooms

8.2 Data collection

The device used to collect data from classrooms is REED Thermo-Anemometer model SD-4214 as shown in Fig. 9 . Table 11 shows parameters, range, resolution and accuracy details of the same device .

To facilitate the data collection in the classrooms and get more accurate information, the data collection process carried out in two phases as following :

Number of sitting places Number of windows Number of doors Door type

9. Methodology of the study

Equipment Parameters

REED SD-4214 Hot Wire ThermoAnemometer/Data Logger Air velocity

Air temperature

Range Resolutions

0.2 - 5.0 m/s 0.01 m/s

5.1 - 25.0 m/s 0.1 m/s

-50 - 1300 C°

-50.1 - 100 C°

0.1 C°

Accuracy

± ( 1% + 0.1 m/s )

± ( 0.4% + 0.5 C° )

± ( 0.4% + 1 C° )

Fig. 6 Plans of the selected classrooms

Table. 11 Details of the experimental equipment

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

Comparing Figs 9-14 ( Class A readings ) and 15-18 ( Class B readngs ) indicated that in class A Values of air temperature and air velocity is much closer to the

9. Methodology of the study 9.2 Data collection

7. Methodology of the study

Measurement Phase 1

Classroom A plan Classroom A

Classroom B plan

Classroom B 9.14

1.24

1.79

1.24

1.06

Section A 1

Section A 3

Section A 5

Section A 2

Section A 4

Section A 6

Section B 2

Section B 1

Section B 3

Section B 4

1.27

1.07

7.79

1.95

7.50

0.88

1.07

1.69

1.11

0.60

5.93

Section boundary

Measurement point

North direction

1.75

19

Fig. 7 Division of the classrooms and measurement points

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

12

7. Methodology of the study

9. Methodology of the study 9.2 Data collection

23.4

0.15

23.3 23.2

0.1

23 °C

23.1

0

1

2

3

4

5

6

7

8

9

10

11

23.7

0.25

23.65

0.2

23.6 0.15

23.55 23.5

23.4 °C

23.45

0.05

23

0.3

23.75

Air temperature °C

Air temperature °C

0.2

23.5

0

23.35

0 0

Air velocity

0.35

7

8

9

10

0.25

23.65

0.2

23.6

0.15

23.55 23.5

0.1

23.4 °C 3

4

5

6

7

8

9

10

Time ( in minutes ) 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

11

Air temperature °C

23.7

2

11

0.3

24

Air velocity m/s

Air temperature °C

6

24 °C

24.1

0.3

23.4

13

5

Fig. 12 Air velocity vs air temperature in section A4

23.45

20

4

Fig. 10 Air velocity vs air temperature in section A2

23.75

1

3

Air temperature Air velocity Average air velocity : 0.215 Average air temperature : 23.56

23.8 °C

0

2

Average air temperature : 23.32

23.8

23.35

1

Time ( in minutes )

Air temperature

Average air velocity : 0.211

0.1 0.05

23.4

Time ( in minutes )

23.85

0.35

23.8

0.25

23.6

22.9

23.85

Air velocity m/s

0.3

23.7

23.8 °C

0.25

23.9

0.2

23.8 0.15 23.7 23.6

0.05

23.5

0

23.4

23.5 °C

0.1

Air velocity m/s

23.7 °C

Fig. 11 Air velocity vs air temperature in section A3

Air velocity m/s

23.8

Fig. 9 Air velocity vs air temperature in section A1

0.05 0

0

1

2

3

4

5

6

7

8

9

10

11

Time ( in minutes ) Series2

Average air velocity : 0.172

Series1

Average air temperature : 23.74

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

7. Methodology of the study

9. Methodology of the study 9.2 Data collection Fig. 13 Air velocity vs air temperature in section A5

0.18

24.3

0.16

24.2

0.14

23.4

0.12

23.2

0.1 0.08

23

0.06

22.8

22.6 °C

22.4

0

1

2

3

4

5

6

7

8

9

10

0.25 0.2

24.1

0.15

24 23.9

0.1

23.8

0.04

23.7

0.02

23.6

0

23.5

0.05

23.6 °C 0

11

1

2

3

4

Air temperature

Average air velocity : 0.123

Average air temperature : 23.33

0.25

24.3 0.1

24.2

23.9 °C

0.05

23.9 23.8

0 2

3

4

5

6

7

8

9

10

11

Air temperature °C

0.15

24.4

Air velocity m/s

Air temperature °C

24.5

1

10

0

11

Average air temperature : 23.98

0.18 0.16 0.14

24.5

0.12

24.4

0.1

24.3

0.08

24.2

0.06

24.1 °C

0.04

24.1

0.02

24

0

0

Time ( in minutes )

Air velocity

24.6

0.2

24.6

0

9

24.6 °C

24.7

24.7

24

8

Fig. 16 Air velocity vs air temperature in section B2

24.7 °C

24.1

7

Air temperature

Air velocity

Fig. 14 Air velocity vs air temperature in section A6 24.8

6

Time ( in minutes )

Time ( in minutes )

Average air velocity : 0.078

5

Air velocity m/s

22.6

24.3 °C

Air velocity m/s

23.6

24.4

Air temperature °C

Air temperature °C

23.8

Fig. 15 Air velocity vs air temperature in section B1 0.2

Air velocity m/s

23.9 °C

24

1

2

3

4

5

6

7

8

9

10

11

Time ( in minutes ) Air temperature

Air velocity

Air temperature

21

Average air velocity : 0.108

Average air temperature : 24.45

Average air velocity : 0.073

Air velocity

Average air temperature : 24.39

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

14

7. Methodology of the study

9. Methodology of the study 9.2 Data collection Fig. 17 Air velocity vs air temperature in section B3

Fig. 19 Average air temperature and velocity in class A sections

25.00

0.05

24.50

0.04

24.3

0.03

24.25

0.02

24.2 °C

24.15 0

1

2

3

4

5

6

7

8

9

10

24.91

0.21

24.00 23.50

Average air velocity : 0.03

22.00

0

0

11

1

2

3

Average air velocity

24.1 24

24.50

0.03

23.9

0.02

23.6 °C

0.01

23.5

0 2

3

4

5

6

7

8

9

10

Time ( in minutes ) Air temperature

15

0.05 0.04

23.6

22

25.00

Average air velocity : 0.034

11

Air temperature °C

24.2

0.06

Air velocity m/s

Air temperature °C

24.3

1

6

0.00 7

Average air temperature : 23.89 Standard deviation : 0.65 Standard air temperature : 23.00

Fig. 20 Average air temperature and velocity in class B sections

24.3 °C

0

5

Average air temperature

Average air velocity : 0.14 Standard deviation : 0.07

Average air temperature : 24.31

Fig. 18 Air velocity vs air temperature in section B4

23.7

4

Class section

Standard air velocity : 0.17

23.8

0.10 0.05

0.04

Air velocity

24.4

0.11

23.33 0.08

23.00

Time ( in minutes ) Air temperature

0.15

23.74

23.56

23.36

22.50

0.01

0.20 24.45

0.17

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

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

24.2

0.25 0.22

Air velocity m/s

24.35

25.50

0.06

Air temperature °C

Air temperature °C

24.4

0.07

Air velocity m/s

24.4 °C

24.45

Class section

Air velocity

Average air temperature : 24.02

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

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

7. Methodology of the study 9. Methodology of the study 9.2 Data collection Section No.

Air temperature ranking

Air velocity ranking

Total points

Final ranking

Section No.

Air temperature ranking

Air velocity ranking

Total points

Final ranking

A1

2

2

10

1 . A1

B1

1

1

8

1. B1

A2

6

6

2

2 . A4

B2

4

2

4

2. B4

A3

3

3

8

3 . A3

B3

3

4

3

3. B2

A4

4

1

9

3 . A5

B4

2

3

5

3. B3

A5

1

5

8

4 . A6

A6

5

4

5

5 . A2

Table 12 : Ranking of sections of Classroom A based on how close their air temperatures and velocities averages are to standard values

Classroom A plan

Classroom B plan

1

3

4

0.211 m/s 23.32 °C

0.215 m/s 23.56 °C

0.078 m/s 23.33 °C

2

5

0.172 m/s 23.74 °C

0.108 m/s 24.45 °C

6 0.044 m/s 24.91 °C

Table 13 : Ranking of sections of Classroom B based on how close their air temperatures and velocities averages are to standard values

Fig. 21 Ranking of sections of Classroom A based on how close their air temperatures and velocities averages are to standard values

Sections has been ranked based on how close the conditions within them to the comfort conditions. Although the results are too close, The inner sections adjacent to the window got the best results in both classrooms

3 0.073 m/s 24.39 °C

4 0.030 m/s 24.31 °C

1 0.123 m/s 23.98 °C

2

As the result of measurement phase 1 indicates that there is no thing wrong either with air temperature or air velocity in both classrooms as temperature readings are compitable with ASHRAE 55 in all measurment points and air velocities are less than 0.25 m/s which is very acceptable according to Toftumm (6.

Toftumm 2004), 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 represent

0.034 m/s 24.02 °C

Fig. 22 Ranking of sections of Classroom B based on how close their air temperatures and velocities averages are to standard values

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

16

7. Methodology of the study

9. Methodology of the study 9.2 Data collection 7.3.2 Measurement Measurement PhasePhase 2 2 Classroom A plan

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

29

17

19

18

39

19

30

20

20

21

10

22

1

23

2

24

40

25

31

26

21

27

11

28

41

29

32

30

22

31

12

32

3

33

42

34

33

35

23

36

13

37

4

38

43

39

34

40

24

41

14

42

5

43

6

44

44

45

35

46

25

47

15

48

36

49

26

50

16

51

7

52

37

53

27

54

17

55

8

56

38

57

28

58

18

59

9

60

45

Classroom B plan

Fig. 22 Division of the classrooms A in measurement phase 2 Seat No.

Mean air velocity

18

0.24

22.68

37

0.24

22.70

1

0.12

21.57

19

0.13

22.79

38

0.23

22.65

2

0.25

21.61

20

0.15

22.96

39

0.20

22.60

16

0.13

22.17

33

0.08

21.75

3

0.13

22.08

21

0.13

22.95

40

0.12

22.75

17

0.10

22.17

34

0.17

21.57

23.00

23.40

22.44

0.22

0.07

0.10

22

1

4

41

0.12

22.94

2

0.08

22.50

18

0.08

22.00

35

0.09

21.67

5

0.20

22.17

23

0.23

22.59

42

0.16

23.10

3

0.15

22.40

19

0.07

22.00

36

0.08

21.73

0.08

21.79

Mean air Temperature

Seat No.

Mean air velocity

Mean air Temperature

6

0.15

22.35

24

0.13

22.79

43

0.21

22.73

4

0.06

22.37

20

0.10

21.96

37

7

0.19

22.29

25

0.15

22.73

44

0.14

23.00

5

0.06

22.25

21

0.09

21.90

38

0.06

21.90

0.14

22.89

0.09

22.33

22

0.07

21.90

39

0.12

21.86

8

0.11

22.44

26

45

0.11

22.79

6

9

0.23

22.50

27

0.23

22.85

46

0.23

22.81

7

0.08

22.40

23

0.09

21.93

40

0.13

21.87

10

0.20

22.49

28

0.26

22.74

47

0.24

22.72

8

0.10

22.27

24

0.13

21.90

41

0.14

21.43

0.20

22.59

0.09

22.37

25

0.09

21.85

42

0.15

21.54

11

0.20

22.48

29

48

0.16

22.79

9

12

0.23

22.67

30

0.13

22.77

49

0.11

22.89

10

0.08

22.37

26

0.14

21.57

43

0.10

21.60

13

0.23

22.69

31

0.29

22.70

50

0.19

22.90

11

0.12

22.13

27

0.09

21.65

44

0.16

21.59

0.25

22.71

12

0.15

22.09

28

0.08

21.69

45

0.15

21.70

13

0.08

22.17

29

0.08

21.70

Average

0.10

21.98

14

0.09

22.24

30

0.15

21.70

15

0.10

22.23

31

0.10

21.70

32

0.10

21.70

14

0.25

22.49

32

51

0.20

22.81

15

0.11

22.71

33

0.14

23.05

52

0.24

22.84

16

0.13

22.85

34

0.13

23.01

53

0.16

22.96

17

0.19

22.87

35

0.11

22.97

54

0.22

22.96

36

0.22

22.81

55

0.30

22.87

56

0.23

22.81

57

0.24

22.72

58

0.16

22.79

59

0.11

22.89

60

0.19

22.90

Average

0.18

22.70

Table 10 Reading averages for classroom A in measurement phase 2

17

Fig. 23 Division of the classrooms B in measurement phase 2

Table 11 Reading averages for classroom A in measurement phase 2

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

9. Methodology of the study 9.2 Data collection

7. Methodology of the study Classroom A plan

Fig. 24 : Air temperature vs air velocity for class A seatings

26.00

0.35

0.30 25.00

0.25

60

59

58

57

56

55

54

53

52

51

50

49

48

47

46

45

44

43

42

41

40

39

38

37

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

24.00

Air temperature Air Velocity m/s

Air Temperature C°

0.20

23.00

S60 22.90 °C

S20 22.96 °C

0.10

S1 21.57 °C 0.05

20.00

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

21.00-22.00 C° 22.01-23.00 C° 23.01-26.00 C°

0.15

22.00

21.00

Cool Slight Cool Comfort zone

Red points indicate clearly that most of the values are not included within ASHRAE 55 comfort zone, although these readings are not cmpitable with ASHRAE 55, almost all of them are located within 1 degree down the limit ( between 22 and 23 °C ) what might not be a significant issue .

0.00

Seat No.

ASHRAE 55 recommended thermal limit

Air temperature reference point

Mean air Temperature

Mean air velocity

Air velocity reference point

Inlet location

26

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

18

9. Methodology of the study 9.2 Data collection

7. Methodology of the study Classroom B plan

Fig. 25 : Air temperature vs air velocity for class B seatings 0.18

26.00

9 25.50

8

0.16

7

25.00

6

0.14 24.50

5 4

0.12

24.00

3

S1 23.40 °C

23.00

2

0.10

0.08

Air Velocity m/s

Air Temperature C°

23.50

1

18

28

38

17

27

37

16

26

36

45

15

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

22.50

Air temperature 0.06

22.00

21.50

S45 21.70 °C

21.00

0.04

0.02 20.50

0.00

20.00

1

2

3

4

5

6

7

8

9

10

11 12

13

14

15 16

17

18

19 20

21

22

23 24

25

26

27 28

29

30

31 32

33

34

35

36

37

38

39

40

41

42

43

44

45

Seat No.

ASHRAE 55 recommended thermal limit

Air temperature reference point

Mean air Temperature

Mean air velocity

Cool Slight Cool Comfort zone

21.00-22.00 C° 22.01-23.00 C° 23.01-26.00 C°

Air temperature readings in classroom B are much farther from ASHRAE 55 comfort zone as air temperature in many locations / seating places lays between 22 and 21 °C Air velocity reference point

Inlet location

2719

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

Methodology of the studystudy 9.7.Methodology of the

Table 14 : Evaluation of classroom A's readings

Table 15 : Evaluation of classroom B's readings

53

52

51

50

49

48

47

46

45

44

43

42

41

40

39

38

37

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

30

29

20

19

10 1

31 21 11

2

32 22 12

3

33 23 13

4

34 24 14

5

35 25 15

6

36 26 16

39

54

40

55

41

56

42

57

43

58

44

59

45

60

7

Mean air Temperature 23.40 22.50 22.40 22.37 22.25 22.33 22.40 22.27 22.37 22.37 22.13 22.09 22.17 22.24 22.23 22.17 22.17 22.00 22.00 21.96 21.90 21.90 21.93 21.90 21.85 21.57 21.65 21.69 21.70 21.70 21.70 21.70 21.75 21.57 21.67 21.73 21.79 21.90 21.86 21.87 21.43 21.54 21.60 21.59 21.70

37

Mean air velocity 0.07 0.08 0.15 0.06 0.06 0.09 0.08 0.10 0.09 0.08 0.12 0.15 0.08 0.09 0.10 0.13 0.10 0.08 0.07 0.10 0.09 0.07 0.09 0.13 0.09 0.14 0.09 0.08 0.08 0.15 0.10 0.10 0.08 0.17 0.09 0.08 0.08 0.06 0.12 0.13 0.14 0.15 0.10 0.16 0.15

27

Seat No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

17

Classroom B plan

8

Mean air Temperature 21.57 21.61 22.08 22.44 22.17 22.35 22.29 22.44 22.50 22.49 22.48 22.67 22.69 22.49 22.71 22.85 22.87 22.68 22.79 22.96 22.95 23.00 22.59 22.79 22.73 22.89 22.85 22.74 22.59 22.77 22.70 22.71 23.05 23.01 22.97 22.81 22.70 22.65 22.60 22.75 22.94 23.10 22.73 23.00 22.79 22.81 22.72 22.79 22.89 22.90 22.81 22.84 22.96 22.96 22.87 22.81 22.72 22.79 22.89 22.90

38

Mean air velocity 0.12 0.25 0.13 0.10 0.20 0.15 0.19 0.11 0.23 0.20 0.20 0.23 0.23 0.25 0.11 0.13 0.19 0.24 0.13 0.15 0.13 0.22 0.23 0.13 0.15 0.14 0.23 0.26 0.20 0.13 0.29 0.25 0.14 0.13 0.11 0.22 0.24 0.23 0.20 0.12 0.12 0.16 0.21 0.14 0.11 0.23 0.24 0.16 0.11 0.19 0.20 0.24 0.16 0.22 0.30 0.23 0.24 0.16 0.11 0.19

28

Seat No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

18

Classroom A plan

9

9.2 Data collection

Fig. 26 : Graphical distribution for tables 14 and 15 in classrooms A and B plans respectively

According to the Cool result of measureSlight Coolphase 1, Secment tions Comfort of zoneeach classroom have been ranked and ordered based on how close the averages of air temperature and air velocity of each of them to the refference average values in Table 2 .

Tables 12 and 13 illustrate the ranking of classrooms A and B sections respectively and Fig. 13 represents this thanking graphically for both classrooms .

Fig. 13 indicates that the the best sections in both classrooms in general are the ones in th front and center of the classroom .

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

20

7. Methodology of the study

9. Methodology of the study

7.3 CFD simulation of the current situation

9.3 CFD simulation

9.3.1 Grid Independence Test

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 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

21

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

7. Methodology of the study

9. of the study CFDMethodology simulation 9.3 simulation GridCFD Independence Test

9.3.1 Grid Independence Test

Mesh sizing configuration in Ansys

Classroom and reference points

Coarse

Medium

Fine

Classroom A

1

2

3

4

5

6

7

8

9

10

Nodes = 2121 Elements = 9130

Nodes = 11905 Elements = 58431

Nodes = 53423 Elements = 280999

Nodes = 56448 Elements = 300385

Nodes = 12078 Elements = 59912

Nodes = 1993 Elements = 8863

Classroom B

1

2

3

4

5

6

7

8

9

10

Supply air temperature = 22 C° , Supply air velocity = 2 m/s

1 Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

22

9. Methodology of the study

7. Methodology of the study 9.3 CFD simulation CFD simulation Grid Independence Test

9.3.1 Grid Independence Test

Classroom A plan

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 13 : Grid independent test on Classroom A, Supply air temperature = 22 °C, Supply air velocity = 2 m/s

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)

Supply air temperature = 22 C°, Supply air velocity = 2 m/s 22.60 22.40 Air Temperature C°

Air Temperature C°

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

22.20 22.00 21.80 21.60

0

1

2

3

4

5

6

7

8

9

10

11

21.40 0

1

2

3

4

Seat No. Fine mesh size

Fig. 21 : Three mesh sizes comparison for classroom A status quo

1

23

Medium mesh size

5

6

7

8

9

10

11

Seat No. Coarse mesh size

Fine mesh size

Medium mesh size

Coarse mesh size

Fig. 22 : Three mesh sizes comparison for classroom B status quo

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

7. Methodology of the study 7.3 CFD simulation

9. Methodology of the study 9.3 CFD simulation 9.3.2 CFD simulation of the current conditions of Classroom A

7.3.1 CFD simulation of of status quo

7.3.1.1 CFD simulation of the current status of Classroom A

1

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

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9. Methodology of the study 9.3 CFD simulation 9.3.2 CFD simulation of the current conditions of Classroom A Fig. 27 : CFD simulation for Classroom A's status quo

comfort zone

Air velocity m/s

comfort zone

comfort zone

comfort zone

Air temperature C°

Supply air temperature = 22 C° , Supply air velocity = 2 m/s

25

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

7.

Methodology of the study 9. Methodology of the study CFD simulation 9.3 CFD simulation

9.3.2 CFD simulation of the current conditions of Classroom A

Air temperature distribution Air temperature distribution

81% below 23 °C

Compatibility with ASHRAE 55 Air velocity distribution

90% below 25 m/s

PMV = -1.14

Supply air temperature = 22 C° , Supply air velocity = 2 m/s

1 Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

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7. Methodology of the study 7.3 CFD simulation

9. Methodology of the study 9.3 CFD simulation 9.3.3 CFD simulation of the current conditions of Classroom B

7.3.1 CFD simulation of of status quo

7.3.1.2 CFD simulation of the current status of Classroom B

1

27

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

9. Methodology of the study 9.3 CFD simulation

7. simulation Methodology ofcurrent the study 9.3.3 CFD of the conditions of Classroom B CFD simulation

Fig. 27 : CFD simulation for Classroom B's status quo

1

comfort zone

Air velocity m/s

comfort zone

comfort zone

comfort zone

Air temperature C°

Supply air temperature = 22 C° , Supply air velocity = 2 m/s

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

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9. Methodology Methodology of the 7. of the studystudy 9.3 CFD simulation CFD simulation

9.3.3 CFD simulation of the current conditions of Classroom B

Air temperature distribution Air temperature distribution

96% below 23 °C

Compatibility with ASHRAE 55 Air velocity distribution

93% below 25 m/s

PMV = -1.32

Supply air temperature = 22 C° , Supply air velocity = 2 m/s

1 29

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

7. Methodology of the study

9.

7.4Methodology CFD simulation of the study 9.3 CFD simulation

9.3.4 CFD simulation of proposed scenarios

7.4.2 CFD simulation of proposed scenarios Supply

Return

Return

Supply

Return Supply

Supply

Supply

Supply

1. Mixing ventilation (MV)

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

Raising supply air temperature to 24 °C and velocity to 2 m/s

1.1 Retain ceiling diffusers configuration

1.2 Changing ceiling diffusers configuration

1 Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

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9. Methodology of the study

7.4 Proposed scenarios

9.3 CFD simulation 9.3.4 CFD simulation of proposed scenarios

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

31

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

10. Results and discussion 10.3 CFD simulation of the study 7. Methodology

7.4 CFD simulation 10.3.4 CFD simulation of proposed scenarios 10.3.4.1 Scenario 1 : Mixing ventilation (MV 1)

Senario 1 Mixing ventilation (MV)

Classroom A

Classroom B

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

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7. Methodology of the study

CFD simulation Scenario 1 (MVand 1) discussion 10.

Results 10.3 CFD simulation

10.3.4 CFD simulation of proposed scenarios 10.3.4.1 Scenario 1 : Mixing ventilation (MV 1)

Classroom A in Scenario 1.1

Classroom B in Scenario 1.1

Air temperature

Air temperature

Air velocity

Air velocity Comfort zone

1 33

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

10.

Results and 7. Methodology of discussion the study 10.3 simulation CFDCFD simulation

10.3.4 CFD simulation of proposed scenarios 10.3.4.1 Scenario 1 : Mixing ventilation (MV 1)

Classroom A in Scenario 1.1 Compatibility with ASHRAE 55

Air temperature distribution

Classroom B in Scenario 1.1 PMV = -0.52

Air velocity distribution

Compatibility with ASHRAE 55

Air temperature distribution

PMV = -0.47

Air velocity distribution

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7. Methodology of the study

10.

CFDResults simulation and discussion 10.3 CFD1.1 simulation Scenario (MV 2)

10.3.4 CFD simulation of proposed scenarios 10.3.4.2 Scenario 1.1 : Mixing ventilation (MV 2)

Classroom A in Scenario 1.2

Classroom B in Scenario 1.1

Air temperature

Air temperature

Air velocity

Air velocity

1 35

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

10.

Results and 7. Methodology of discussion the study 10.3 simulation CFDCFD simulation

10.3.4 CFD simulation of proposed scenarios 10.3.4.2 Scenario 1.1 : Mixing ventilation (MV 2)

Classroom A in Scenario 1.1 Compatibility with ASHRAE 55

Air temperature distribution

Classroom B in Scenario 1.1 PMV = -0.54

Air velocity distribution

Compatibility with ASHRAE 55

Air temperature distribution

PMV = -0.16

Air velocity distribution

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10. Results and discussion 7. Methodology of the study 10.3 CFD simulation

7.4 CFD simulation

10.3.4 CFD simulation of proposed scenarios 10.3.4.3 Scenario 2 : Displacement ventilation (DV)

Senario 2 Displacement ventilation (DV)

Classroom A

37

Classroom B

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

7. Methodology of the study

10.

CFDResults simulation and discussion 10.3 CFD2simulation Scenario (DV)

10.3.4 CFD simulation of proposed scenarios 10.3.4.3 Scenario 2 : Displacement ventilation (DV)

Classroom A in Scenario 2

Classroom B in Scenario 2

Air temperature

Air temperature

Air velocity

Air velocity

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10.

Results and 7. Methodology of discussion the study 10.3 simulation CFDCFD simulation

10.3.4 CFD simulation of proposed scenarios 10.3.4.3 Scenario 2 : Displacement ventilation (DV)

Classroom A in Scenario 1.1 Compatibility with ASHRAE 55

Air temperature distribution

Classroom B in Scenario 1.1 PMV = -0.13

Air velocity distribution

Compatibility with ASHRAE 55

Air temperature distribution

PMV = -0.15

Air velocity distribution

1 39

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

10. Results and discussion 7. simulation Methodology of the study 10.3 CFD

7.4 simulation CFD simulation 10.3.4 CFD of proposed scenarios 10.3.4.4 Scenario 3 : Stratum ventilation (SV)

Senario 3 Stratum ventilation (SV)

Classroom A

Classroom B

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

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7. Methodology of the study

CFDResults simulation and discussion 10.

10.3 CFD3simulation Scenario (SV)

10.3.4 CFD simulation of proposed scenarios 10.3.4.4 Scenario 3 : Stratum ventilation (SV)

Classroom A in Scenario 1.2

Classroom B in Scenario 1.1

Air temperature

Air temperature

Air velocity

Air velocity

1 41

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

10.

Results and 7. Methodology of discussion the study 10.3 simulation CFDCFD simulation

10.3.4 CFD simulation of proposed scenarios 10.3.4.4 Scenario 3 : Stratum ventilation (SV)

Classroom A in Scenario 1.1 Compatibility with ASHRAE 55

Air temperature distribution

Classroom B in Scenario 1.1 PMV = -0.10

Air velocity distribution

Compatibility with ASHRAE 55

Air temperature distribution

PMV = -0.14

Air velocity distribution

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7. Methodology of the study

10.

CFDResults simulationand discussion 10.3 CFD simulation

Evaluating scenarios

10.3.5 Evaluating scenarios

Fig. 34 : Comparing scenarios based on PMV values according to ASHRAE Standard 55-2017 Classroom

Status quo

MV 1 scenario

MV 2 scenario

DV scenario

Classroom A

PMV value = -1.14

PMV value = -0.52

PMV value = -0.54

PMV value = -0.13

SV scenario

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

Classroom B

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 43

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

7. Methodology of the study

CFD simulation 10. Results and discussion 10.3 CFD simulation Evaluating scenarios 10.3.5 Evaluating scenarios 1.5

1

0.5

Status Quo 0

A

B

-0.5

MV1 A

-0.52

MV2 B

-0.47

A

DV

SV

B

A

B

A

B

-0.16

-0.13

-0.15

-0.10

-0.14

-0.54

-1 -1.14

-1.5

-1.32

Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi

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11. Conclusion

12. Acknowledgments

This study was conducted to enhance thermal sensation in KAU classrooms by testing and comparing several mechanical ventilation strategies using CFD simulation, the main conclusion of the present work can be summarized in the following points :

The author would like to express gratitude to Dr-Ing. Mohannad Bayoumi, Course Instructor, for giving me a numerous consultations and guidelines throughout the semester .

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 .

In addition, a thank you to Dr. Salah Hafiz from Aerospace Engineering Department , Faculty of Engineering who introduced a valuable consultations in aerodynamics related issues.

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 .

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13. References [1] Giuli, V. De, Da, O., & Carli, M. De. (2012). Indoor environmental quality and pupil perception in Italian primary schools. Building and Environment, 56, 335–345.

[8] B. Cao, Y. Zhu, Q. Ouyang, X. Zhou, L. Huang, Field study of human thermal comfort and thermal adaptability during the summer and winter in Beijing, Energy Build. 43 (2011) 1051–1056.

[2] Kumar, M., Ooka, R., Rijal, H. B., Kumar, S., & Kumar, A. (2019).

Energy & Buildings Progress in thermal comfort studies in classrooms over last 50 years and way forward. Energy & Buildings, 188– 189, 149–174. https://doi.org/10.1016/j.enbuild.2019.01.051

[9] Z. Wang, A. Li, J. Ren, Y. He, Thermal adaptation and thermal environment in university classrooms and offices in Harbin, Energy Build. 77 (2014) 192–196.

[3] Toftum, Jorn. (2004). Air movement - Good or bad?. Indoor air. 14 Suppl 7. 40-5. 10.1111/j.1600-0668.2004.00271.x.

[4] Guenther, Sebastian. “What Is PMV? What Is PPD? The Basics of Thermal Comfort.” www.simscale.com. Last modified September 18, 2019. https://www.simscale.com/blog/2019/09/what-is-pmvppd/.

[5] P.F. Hu, W. Liu, Z.N. Jiang, Study on the indoor thermal sensation of young college students in the area which is hot in summer and cold in winter, Int.J. Arch. Sci. 7 (2006) 47–52.

[10] Z. Wang, H. Ning, X. Zhang, Y. Ji, Human thermal adaptation based on university students in China’s severe cold area, Sci. Technol. Built Environ. (2016),doi: 10.1080/23744731.2016.1255495.

[11] P. Baruah, M.K. Singh, S. Mahapatra, Thermal comfort in naturally ventilated classrooms, PLEA -2014 Conference, December 16–18, 2014.

[12] R. Vittal, S. Gnanasambandam, Perceived thermal environment of naturally ventilated classrooms in India, Creat. Space 3 (2016) 149–165.

[6] G. Zhang, C. Zhenga, W. Yanga, Q. Zhanga, D.J. Moschandreasa, Thermal comfort investigation of naturally ventilated classrooms in a subtropical region,Indoor Built Environ. 16 (2007) 148–158.

[7] R. Yao, J. Liu, B. Li, Occupants’ adaptive responses and perception of thermal environment in naturally conditioned university classrooms, Appl. Energy 87 (2010) 1015–1022.

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Improving thermal sensation in classrooms with respect to draft avoidance by optimizing the mechanical air supply method - Omar Hussein Al-hebshi