REDUCING INDOOR AIR CONTAMINANTS INSIDE A CAMPUS …eprints.utm.my/id/eprint/77791/1/NoorEmiliaAhmadPFKM2016.pdf · 2018-07-02 · ruangan bas akan menyebabkan pelbagai penyakit seperti

REDUCING INDOOR AIR CONTAMINANTS INSIDE A CAMPUS BUS

PASSENGER COMPARTMENT

NOOR EMILIA BINTI AHMAD SHAFIE

A thesis submitted in fulfilment of the

requirements for the award of the degree of

Doctor of Philosophy (Mechanical Engineering)

Faculty of Mechanical Engineering

Universiti Teknologi Malaysia

MARCH 2016

iii

This is dedicated to my beloved husband (Dr. Iqbal Bin Mokhtar) and

parents (Ahmad Shafie Bin Ariffin, Noor Lida Binti Raffie, Mokhtar Bin Ahmad

& Sabariah Binti Md. Kassim).

iv

ACKNOWLEDGEMENT

I would like to express my deepest gratitude to Dr. Haslinda Binti Mohamed

Kamar the main supervisor, for her guidance, support, understanding and

encouragement over the past years. I would like to thank to Assoc. Prof. Dr. Nazri

Bin Kamsah the co-supervisor, for his encouragement, advice, understanding and

support.

I am indebted to University Teknologi Malaysia (UTM) and the Ministry of

Higher Education for providing the funding on this PHD study (Vot No. 06H75).

Thanks are extended to Mr. Khairul Nizam Bin Mod Noh for providing

professional technical assistance in UTM bus service. Thanks are also given to MD

Interactive and Exact Analytical for supplying and providing professional technical

assistance in instrumentation and measurement.

Finally, I want to express my gratitude to my husband, parents and friends for

their fully support and love.

v

ABSTRACT

Good ventilation system is important to provide fresh air and comfortable

environment for passengers. Lack of fresh air inside a bus compartment may cause

various illnesses such as headache, asthma, cardiovascular and lung cancer. Two

factors influence the ventilation system effectiveness namely the arrangement of air

supply diffusers and the air return grilles. This thesis presents a study on air

contaminants inside a university’s bus passenger compartment. The goal is to find a

suitable ventilation arrangement that can reduce the concentration of the air

contaminants. First a field measurement was carried out on a selected bus to measure

the air contaminants at the front section, middle section and rear section. The

contaminants include carbon monoxide, carbon dioxide, formaldehyde and

particulate matter. Then computational fluid dynamics flow analyses were carried out

on simplified model of the bus compartment employing renormalization group k-ε

model for air flow, species transport for gases and discrete phase for particles. Five

cases of ventilation arrangements were considered namely displacement ventilation

with two air return grilles, underfloor air distribution with two air return grilles,

mixing ventilation with four air return grilles, displacement ventilation with four air

return grilles and underfloor air distribution with four air return grilles. It was found

from the field measurements that the concentration of carbon monoxide, carbon

dioxide, formaldehyde, particulate matter 1, particulate matter 2.5 and particulate

matter 10 were 7 ppm, 1102 ppm, 0.18 ppm, 52 µg/m3, 52 µg/m3 and 51 µg/m3,

respectively. Results of flow simulations show that the underfloor air distribution

with four air return grilles is able to reduce the contaminants concentration inside the

passenger compartment. On average, the concentrations of carbon monoxide, carbon

dioxide, formaldehyde, particulate matter 1, particulate matter 2.5 and particulate

matter 10 were reduced by about 40%, 10%, 38%, 37%, 33% and 30%, respectively.

vi

ABSTRAK

Sistem pengudaraan yang baik adalah penting untuk memberikan udara segar

dan persekitaran yang selesa kepada penumpang. Kekurangan udara di dalam

ruangan bas akan menyebabkan pelbagai penyakit seperti sakit kepala, asma, sakit

jantung dan kanser paru-paru. Dua faktor mempengaruhi keberkesanan sistem

pengudaraan iaitu susun atur sistem bekalan udara peresap dan jeriji udara pulangan.

Tesis ini membentangkan kajian terhadap bahan cemar udara di dalam ruangan

penumpang bas universiti. Matlamat kajian ini adalah untuk mencari susun atur

sistem pengudaraan yang sesuai bagi mengurangkan kepekatan bahan cemar udara.

Pertama pengukuran lapangan telah dijalankan pada bas yang telah dipilih untuk

mengukur bahan cemar pada bahagian depan, bahagian tengah dan bahagian

belakang. Bahan cemar ini terdiri daripada karbon monoksida, karbon dioksida,

formaldehid dan zarah. Kemudian analisis aliran pengkomputeraan dinamik bendalir

telah dijalankan pada model ruangan bas dengan menggunakan model

renormalization group k-ε untuk aliran udara, species transport untuk gas dan

discrete phase untuk zarah. Lima kes susun atur pengudaraan iaitu pengudaraan

anjakan dengan dua jeriji udara pulangan, pengudaraan udara bawah lantai dengan

dua jeriji udara pulangan, pengudaraan percampuran dengan empat jeriji udara

pulangan, pengudaraan anjakan dengan empat jeriji udara pulangan dan pengudaraan

udara bawah lantai dengan empat jeriji udara pulangan telah dikaji. Didapati

daripada data pengukuran dimana tahap kepekatan karbon monoksida, karbon

dioksida, formaldehid, zarah 1, zarah 2.5 dan zarah 10 adalah 7 ppm, 1102 ppm,

0.18 ppm, 52 µg/m3, 52 µg/m3 dan 51 µg/m3, masing-masing. Keputusan simulasi

aliran menunjukkan pengudaraan udara bawah lantai dengan empat jeriji udara

pulangan mampu mengurangkan tahap kepekatan bahan cemar di dalam ruangan

penumpang. Secara purata, tahap kepekatan karbon monoksida, karbon dioksida,

formaldehid, zarah 1, zarah 2.5 dan zarah 10 telah berkurang sebanyak 40%, 10%,

38%, 37%, 33% dan 30%, masing-masing.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xi

LIST OF FIGURES xiv

LIST OF ABBREVIATIONS xvii

LIST OF SYMBOLS xix

LIST OF APPENDICES xx

1 INTRODUCTION 1

1.1 Introduction 1

1.2 Problem Statement 4

1.3 Objectives of the Research 4

1.4 Scopes of the Research 5

1.5 Important of the research 6

1.6 Thesis Outline 6

viii

2 LITERATURE REVIEW 8

2.1 Introduction 8

2.2 Indoor Air Contaminant 9

2.2.1 Gas Contaminants 10

2.2.2 Particle Contaminants 12

2.2.3 Standards and Guidelines of Indoor Air

Contaminant 13

2.2.4 Effects of Indoor Air Contaminants on

Human Health 14

2.2.5 Contaminant Concentration Level in a Bus

Passenger Compartment 17

2.3 Bus Transportation System 26

2.3.1 Types of Bus Service 26

2.3.2 Air-Conditioning System 28

2.4 Ventilation 30

2.4.1 Types of Ventilation System 31

2.4.1.1 Mixing Ventilation 31

2.4.1.2 Displacement Ventilation 33

2.4.1.3 Underfloor Air Distribution 34

2.5 Computational Fluid Dynamics Analysis on

Ventilation System 36

2.6 Summary and Research Gap 51

3 METHODOLOGY 53

3.1 Introduction 53

3.2 Field Measurement 55

3.2.1 Test Instrument 58

3.2.2 Test Procedure of Gas and Particle

Detections 61

ix

3.3 Computational Fluid Dynamics Analysis 63

3.3.1 Geometry (Baseline Model) 64

3.3.2 Mesh and Grid Verification 67

3.3.3 Boundary Conditions and Properties 72

3.3.4 Governing Equation and Finite Volume

Method 80

3.3.5 Solver, Solution Methods and

Convergence 83

3.3.6 Verification 85

3.3.6.1 Air Flow Model 85

3.3.6.2 Discretization Scheme 87

3.3.6.3 Numerical Iteration 87

3.3.6.4 Uncertainty and Error in CFD

Simulation 89

3.3.6.5 Uncertainty and Error in Field

Measurement 90

3.3.7 Validation 95

3.3.7.1 Validation on Air Contaminants

Concentration 95

3.4 Parametric Analysis (Cases) 98

3.5 Summary 103

4 RESULTS AND DISCUSSION 104

4.1 Indoor Air Contaminants Concentration 104

4.1.1 Field Measurements on Gas and

Particle Concentrations 105

4.1.2 Statistical Analysis 111

4.1.3 Summary 113

4.2 CFD Simulation on Ventilation System Design 114

4.2.1 Effects of Ventilation System Design

on Air Contaminants Concentration

(Baseline Case) 114

x

4.2.1.1 Spatial Distribution of Gases

Concentration in the Entire

Bus Compartment 117

4.2.1.2 Spatial Distribution of Particles

Concentration in the Entire

Bus Compartment 121

4.2.2 Effects of Ventilation System Design

on Air Contaminants Concentration

(Parametric Analysis) 126

4.2.2.1 Case 1 (MV+DV&2RG) 127

4.2.2.2 Case 2 (MV+UFAD&2RG) 131

4.2.2.3 Case 3 (MV&4RG) 135

4.2.2.4 Case 4 (MV+DV&4RG) 139

4.2.2.5 Case 5 (MV+UFAD&4RG) 143

4.3 New Ventilation System Design 148

4.3.1 Spatial Distribution of Gases

Concentration in the Entire Bus

Compartment 150

4.3.2 Spatial Distribution of Particles

Concentration in the Entire Bus

Compartment 154

4.3.3 Air Flow Pattern 159

4.3.4 Particulate Matter Transport Pattern 161

4.3.5 Summary 163

5 CONCLUSIONS AND RECOMMENDATIONS 164

5.1 Conclusions 164

5.2 Recommendations of Future Work 166

REFERENCES 167

Appendices A-I 177-219

xi

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Sources of gas contaminants 11

2.2 Sources of particle contaminants 12

2.3 Comparison of indoor environment standards and

guidelines 13

2.4 Formaldehyde exposure levels in relation

to human health 14

2.5 Types of indoor air quality instruments 24

2.6 Summary of literature review related to indoor

air contaminant inside a bus passenger compartment 25

2.7 Summary of literature review related to ventilation

strategy 48

2.8 Summary of literature review related to CFD

method in analysing ventilation strategy 49

3.1 Description of the bus used for the field

measurements 56

3.2 The range and accuracy of the anemometer, indoor

environmental quality and particle counter

instruments 60

3.3 Dimensions of the CFD model 64

3.4 Types of grid, grid element and grid size 71

3.5 Boundary conditions used in CFD model 76

3.6 Properties of air 79

3.7 Properties of solid 79

xii

3.8 Properties of gas 79

3.9 Properties of particle 79

3.10 Discretizations versus CO and PM1 concentrations 87

3.11 Number of iterations versus gases concentration 88

3.12 Number of iterations versus particles concentration 88

3.13 Uncertainty calculation of CO, CO2 and CH2O

concentrations 89

3.14 Uncertainty calculation of PM1, PM2.5 and PM10

Concentrations

3.15 Uncertainty calculation of CO concentration 91

3.16 Uncertainty calculation of CO2 concentration 92

3.17 Uncertainty calculation of CH2O concentration 92

3.18 Uncertainty calculation of PM1 concentration 93

3.19 Uncertainty calculation of PM2.5 concentration 93

3.20 Uncertainty calculation of PM10 concentration 94

3.21 Validation of CO concentration with field

measurement data 96

3.22 Validation of CO2 concentration with field

measurement data 96

3.23 Validation of CH2O concentration with field

measurement data 96

3.24 Validation of PM1 concentration with field

measurement data 97

3.25 Validation of PM2.5 concentration with field

measurement data 97

3.26 Validation of PM10 concentration with field

measurement data 97

3.27 Detail description of parametric analysis 98

4.1 Statistical results of CO, CO2 and CH2O

concentrations 112

4.2 Statistical results of PM1, PM2.5 and PM10

concentrations 113

4.3 Air contaminants concentration level at the

breathing level 125

xiii

4.4 Comparison of air contaminants concentration

level on each case 147

4.5 Dimensions of a new ventilation system design 149

4.6 Air contaminants concentration level at the

breathing level 158

xiv

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Source of complaints in an enclosed environment 9

2.2 Percentage of passengers on different modes

transportation 10

2.3 Air contaminants from the vehicles exhaust 11

2.4 Types of particle sizes 12

2.5 Different types of particle sizes 15

2.6 The accumulated particles in a human lung 16

2.7 CO2 concentration level versus time 18

2.8 CO concentration level versus time 18

2.9 PM2.5 concentration level versus time 18

2.10 The total vehicles travel in every year in Malaysia 26

2.11 Types of bus services in Malaysia (a) Public

(b) School (c) Highway (d) Factory

(e) University 27

2.12 The schematic layout of air-conditioning system 28

2.13 The schematic of a roof package unit 29

2.14 The schematic of a floor package unit 30

2.15 Mixing ventilation systems 32

2.16 Short circuiting flow phenomenon 32

2.17 Displacement ventilation systems 33

2.18 The schematic diagram of displacement

ventilation systems 34

2.19 Underfloor air distribution systems 35

xv

2.20 The schematic diagram of underfloor air

distribution systems 35

3.1 Methodology flow chart 54

3.2 Field measurement flow chart 55

3.3 Bus passenger compartment 56

3.4 Location measurements of gases and particles

inside the bus passenger compartment 57

3.5 The in-campus route followed during the field

measurement 58

3.6 Indoor environmental quality instrument (gas) 59

3.7 Indoor environmental quality instrument (particle) 59

3.8 Anemometer instrument 60

3.9 CFD analysis steps flow chart

(baseline case analysis) 63

3.10 Orthogonal diagram of the bus passenger

compartment (a) Top view (b) Side view

(c) Front view 65

3.11 Perspective diagram of the bus passenger

compartment (a) Front view (b) Side view 66

3.12 The concentration level of CO via the number

of elements 67

3.13 The concentration level of PM1 via the number

of elements 68

3.14 The meshed of CFD model 69

3.15 Rectangular Cartesian grids 81

3.16 Rectangular Cartesian grids 82

3.17 Convergence of the gas contaminant (CO) 84

3.18 Convergence of the particle contaminant (PM1) 84

3.19 The comparison of viscous models via CO

concentration 85

3.20 The comparison of viscous models via PM1

concentration 86

3.21 CFD analysis steps flow chart

(parametric analysis) 99

xv

3.22 Case 1 (MV+DV&2RG) 100

3.23 Case 2 (MV+UFAD&2RG) 100

3.24 Case 3 (MV&4RG) 101

3.25 Case 4 (MV+DV&4RG) 101

3.26 Case 5 (MV+UFAD&4RG) 102

4.1 Locations of data collection of gas and

particle concentrations (front section,

middle section and rear section) 104

4.2 CO concentration versus time 105

4.3 CO₂ concentration versus time 106

4.4 CH₂O concentration versus time 107

4.5 PM1 concentration versus time 108

4.6 PM2.5 concentration versus time 109

4.7 PM10 concentration versus time 110

4.8 The components of air contaminants through

the bus door 115

4.9 Top view of the bus passenger compartment

(locations of cross sections A-A’

(front section), B-B’ (middle section)

and C-C’ (rear section) 115

4.10 Sampling locations of air contaminants

concentration level (front section,

middle section and rear section) 116

4.11 Sampling height of air contaminants

concentration level 116

4.12 Spatial distribution of CO concentration

(a) In cross section A-A’ (front section)

(b) In cross section B-B’ (middle section)

(c) In cross section C-C’ (rear section) 118

4.13 Spatial distribution of CO2 concentration

(a) In cross sections A-A’ (front section)



xvi

4.14 Spatial distribution of CH2O concentration




4.15 Spatial distribution of PM1 concentration




4.16 Spatial distribution of PM2.5 concentration








4.18 Top view of the bus passenger compartment

(locations of cross sections A-A’ (plane a-a)

and B-B’ (plane b-b) 126

4.19 Comparison of gas concentrations over the

length of the bus (a) CO (b) CO₂ (c) CH₂O 128

4.20 Comparison of particulate concentrations

over the length of the bus (a) PM1 (b) PM2.5

(c) PM10 130





(c) PM10 134





(c) PM10 138

xvii




Over the length of the bus (a) PM1 (b) PM2.5

(c) PM10 142





(c) PM10 146

4.29 Orthogonal diagram of the bus passenger

compartment (a) Top view (b) Side view

(c) Front view 149

4.30 Spatial distribution of CO concentration

(a) In cross section A-A’ (front section)



4.31 Spatial distribution of CO2 concentration




4.32 Spatial distribution of CH2O concentration








4.34 Spatial distribution of PM2.5 concentration




xviii





4.36 Velocity vectors of a new ventilation system

design (a) CO (b) CO2 (c) CH2O (d) PM1

(e) PM2.5 (f) PM10 160

4.37 Particle trajectories of PM1 concentration 161

4.38 Particle trajectories of PM2.5 concentration 162

4.39 Particle trajectories of PM10 concentration 162

xvii

LIST OF ABBREVIATIONS

ACH - Air exchange rate

ASHRAE - American Society of Heating, Refrigerating and

Air-Conditioning Engineers

BC - Baseline case

BTEX - Benzene, toluene, ethyl-benzene and xylenes

CFD - Computational fluid dynamics

C1 - Case 1

C2 - Case 2

C3 - Case 3

C4 - Case 4

C5 - Case 5

CO - Carbon monoxide

CO₂ - Carbon dioxide

CH₂O - Formaldehyde

DPM - Discrete phase model

DV - Displacement ventilation

EPA - Environment Protection Agency

GCI - Grid convergence index

HPC - Handheld particle counter

H1N1 - Avian influenza and swine influenza

IAQ - Indoor air quality

IAC - Indoor air contaminant

IEQ - Indoor environmental quality

MAHCS - Monoaromatic hydrocarbons

MV - Mixing ventilation

xviii

NIOSH - National Institute for Occupational Safety and Health

NO₂ - Nitrogen dioxide

OSHA - Occupational Safety and Health Administration

O₂ - Oxygen

PPM - Part per million

PMs - Particulate matters

PM1 - Particulate matter 1

PM2.5 - Particulate matter 2.5

PM10 - Particulate matter 10

RANS - Reynolds-averaged Navier-Stokes

RG - Return grille

RNG - Renormalization-group

SARS - Severe acute respiratory syndrome

SD - Standard deviation

SIMPLE - Semi-implicit method for pressure linked equations

SO₂ - Sulphur dioxide

SF6 - Sulphur hexafluoride

TLVs - Threshold limit values

UTM - Universiti Teknologi Malaysia

UFPS - Ultrafine particles

UFAD - Underfloor air distribution

WHO - World Health Organization

xix

LIST OF SYMBOLS

� - Cross sectional area

� - Contaminant

�� - Maximum measured

�� - Maximum predicted

� - Diameter

�� - Hydraulic diameter

� - Gravity

hr - Hour

- Length

m - Meter

m3 - Cubic meter

� � - Mass flowrate of particle

� - Wetted perimeter

Re - Reynold number

ST - Rate of thermal energy production

T - Diffusion coefficient

� - Friction velocity

�, , � - Velocity

� - Distance to the wall

y+ - Non-dimensional number

� - Density

� - Kinematic viscosity

μg - Microgram

xx

LIST OF APPENDICES

APPENDIX TITLE PAGE

A1 University shuttle bus 177

A2 Description of the bus 177

A3 Front section of the bus passenger compartment 178

A4 Rear section of the bus passenger compartment 178

B1 CFD model of Baseline Case 179

B2 CFD model of Case 1 179





C1 CFD Fluent simulation settings 182

D1 CFD Fluent steps flow chart 192

E1 Contour x-z plane of air contaminants (Case 5) 193

E2 Contour y-z plane of air contaminants (Case 5) 196

F1 Ansys license server (ce.utmgrid.utm.my) 199

G1 Samples data 200

G2 Statistical calculations 212

H1 Instrument calibration certificate of gas

contaminants 216

H2 Instrument calibration certificate of particle

contaminants 217

I1 List of publications 218

I2 List of conferences 219

1

CHAPTER 1

INTRODUCTION

1.1 Introduction

Indoor air quality is one of the major environmental concerns since people

spend about 90% of their time indoors and about 7% of their daily time commuting,

mostly between their workplace and their residence [1]. At present, many people use

public transport buses for workplace, shopping, recreation and others [2]. Apart from

public transport buses, university shuttle buses have attracted extensive attention

since many students use this transportation in a university campus to travel to class,

extracurricular activities and others [3].

Indoor air contaminants are typically found inside the bus passenger

compartment namely gases (CO, CO₂, and CH₂O) and particles (PM1, PM2.5 and

PM10) [4]. The air contaminants such as CO, CO₂, CH₂O, PM1, PM2.5 and PM10

originate from mobile sources (exhaust gas) [5]. Based on the previous studies, the

concentration levels of CO, CO₂, CH₂O, PM1, PM2.5 and PM10 were exceeded the

threshold limit values by the World Health Organization guideline [2]. Peak hours,

passenger’s board and unboard, weather condition, ventilation setting, ventilation

system, bus engine and bus age are the factors that influences the air contaminants

2

concentration level inside the bus passenger compartment [6]. The exposure of CO,

CO₂, CH₂O, PM1, PM2.5 and PM10 concentrations could threaten the passenger’s

health in both the short and long term. Air contaminants concentration is responsible

for a wide range of health consequences such as headache, eye irritation, lung cancer,

cardiovascular, tuberculosis, asthma and airborne transmission (Severe Acute

Respiratory Syndrome and Avian Influenza and Swine Influenza) [7]. The particulate

matters such as PM1, PM2.5 and PM10 can penetrate into the thoracic part of the

airway and accumulate in the respiratory system [8]. Particles less than 10 µm in

diameter can be inhaled and 80% of them will be deposited in the human respiratory

system, possibly leading to fatal outcomes [9].

In bus passenger compartments require good ventilation system to provide

fresh air and comfortable environment for passenger. In engineering approach, the

efficiency of ventilation system is evaluated by the indoor air quality. Indoor Air

Quality (IAQ) refers to the effect, good or bad of the contents of the air inside an

enclosed environment [10]. Good IAQ is the quality of air which has no unwanted

contaminants. Poor IAQ occurs when contaminants are present in excessive

concentrations. Knowledge concerning the air contaminants concentration level is

very important to prevent the inhalation of harmful air contaminants by passengers

when commuting in a bus. The ventilation systems of buses must be improved as

bus travel is used for business, shopping, campus, school, recreation or others

activities. Several factors affect the performance of the ventilation system such as air

supply velocity, air supply temperature, layout of the air supply diffusers and layout

of the air return grilles [11].

3

Three types of ventilation system have been widely used in an enclosed

environment such as mixing ventilation, displacement ventilation and underfloor air

distribution [12]. Within the last few years, the mixing ventilation system has

become a popular design and has been used in bus transportation. A common

example of the mixing ventilation system is one equipped with ceiling-based air

supply diffusers and air return grilles [12]. In bus transportation, the air is supplied

via air supply diffusers (placed on the ceiling mounted ducting above passenger

seats) and released through the air return grilles (placed on the roof). Based on the

previous studies, this system is not capable of removing the indoor air contaminants

when the door is opened for boarding and unboarding passengers [2]. This is because

much of the supply air leaves the compartment without mixing with compartment air

due to improper layout of air supply diffusers and air return grilles. When this

situation occurs, the air contaminants will accumulate at the tight space of the

compartment such as on the floor and passenger seats [13]. Therefore, as an

alternative, modification of the present ventilation system is needed to reduce the air

contaminants concentration inside the bus passenger compartment.

The bus ventilation system is very important in order to reduce the air

contaminants concentration level. At present, research works on reducing indoor air

contaminants inside the bus passenger compartment is limited especially using

computational fluid dynamics (CFD) software [14]. CFD software offers an

alternative platform which is more convenient than experimental practice to predict

the indoor air contaminant in various applications [15]. Hence, an investigation of

indoor air contaminants using CFD method is necessity to find a suitable ventilation

system design that would lower the level of air contaminants inside the bus passenger

compartment.

4

1.2 Problem Statement

The present ventilation system in bus is not capable of reducing the air

contaminants. This is due to improper arrangements of the ventilation system such as

the air supply diffusers and the air return grilles. In bus compartment the

concentration level of air contaminants such as gases and particles exceeded the

threshold limit set by the World Health Organization guideline due to improper

arrangements of the ventilation system. The excessive concentration of gas and

particle contaminants could affect passenger’s health when commuting in a bus.

Therefore, the bus ventilation systems need to redesign to reduce the level of air

contaminants. Two methods were identified namely a field measurement and CFD

simulation. The field measurement was carried out to quantify the concentrations of

CO, CO₂, CH₂O, PM1, PM2.5 and PM10 inside the bus. The CFD simulation model

is to predict the air contaminants concentration level inside the bus. Five types of

ventilation system design were considered namely a displacement ventilation with

two air return grilles, underfloor air distribution with two air return grilles, mixing

ventilation with four air return grilles, displacement ventilation with four air return

grilles and underfloor air distribution with four air return grilles.

1.3 Objectives of the Research

Three objectives were developed to achieve the aim of this research. The

following objectives are as follows:

1. To quantify the indoor air contaminants concentration level inside a campus bus

passenger compartment.

2. To examine the effects of present ventilation system design (baseline case) on

contaminants concentration level through the use of CFD method.

3. To establish suitable ventilation system design for reducing the indoor air

contaminants concentration level inside the campus bus passenger compartment.

5

1.4 Scopes of the Research

The scope of this research is divided in two parts, i.e. field measurement and

CFD simulation. The field measurements were carried out in a university shuttle bus

passenger compartment. The distance of bus travelled within a university campus is

48 km. The measurements were conducted during the peak hour period to examine

the gas (CO, CO₂ and CH₂O) and particle (PM1, PM2.5 and PM10) concentration. In

this study, the door is opened during quantification of the air contaminants

concentration inside the bus passenger compartment. The weather condition was

clear and no rain fell while the field measurements were conducted.

Ansys CFD Fluent software (R-14) was used to develop a simplified

three-dimensional model of the bus passenger compartment. The CFD model was

meshed using the tetrahedron elements. In this study, the boundary condition of the

air contaminants was prescribed at the door only due to outside air contaminants

entering the bus. The passenger compartment is assumed clean and without air

contaminants. Three types of air flow analysis namely RNG k-ε turbulent model,

species transport model and discrete phase model were used to predict the

distribution of air flow and air contaminants. Five types of ventilation system design

were considered namely a displacement ventilation with two air return grilles,

underfloor air distribution with two air return grilles, mixing ventilation with four air

return grilles, displacement ventilation with four air return grilles and underfloor air

distribution with four air return grilles. The comparison between the field data and

CFD simulation on various ventilation system designs were discussed.

6

1.5 Important of the Research

Understanding the link between ventilation system design and air

contaminants concentration can help to reduce the level of air contaminants

concentration inside a bus passenger compartment. The reducing of air contaminants

concentration enhances the air quality inside the bus compartment and to prevent the

indoor air diseases to passengers.

1.6 Thesis Outline

Chapter 1 presents an introduction, problem statement, objectives and scopes

of this research.

In Chapter 2, a review on field measurement and CFD simulation on air

contaminants concentration in an enclosed environment are presented. Different

types of air contaminants namely gases and particles are investigated. The effects of

air contaminants on passenger health are also presented in this chapter. The

methodology on a field measurement and CFD analysis on air contaminants

concentration in an enclosed environment has been reviewed. In addition, different

types of ventilation systems such as mixing ventilation, displacement ventilation and

underfloor air distribution in an enclosed environment are presented.

Chapter 3 presents the methodology of this study. The methodology is

divided into two parts, i.e. field measurement and CFD simulation analysis. The field

measurements are conducted to quantify the air contaminants concentration level

inside the bus passenger compartment. The measured data is used for boundary

condition in the CFD model and validation. A three-dimensional CFD model has

7

been developed in order to simulate and predict the air contaminants concentration

inside the bus environment. Five cases of parametric analysis are presented in this

chapter.

In Chapter 4, the results of field measurements and CFD simulation on air

contaminants concentration are presented. The levels of air contaminants

concentration are discussed at the front section, middle section and rear section of the

passenger compartment. The CFD simulations results are discussed based on the

whole bus compartment, passenger seats and breathing level to examine the air

contaminants concentration level. A parametric analysis on the various cases of

ventilation system design is presented in this chapter. A new ventilation system

design that was obtained from the parametric analysis was discussed based on the air

flow and air contaminants.

Chapter 5 presents a conclusion on air contaminant concentration levels

inside the bus passenger compartment. The levels of air contaminants concentration

levels and the effects of present ventilation system are concluded in this chapter. As

well, the best ventilation system designs that reduce the indoor air contaminants

inside the passenger compartment are presented. Several recommendations for future

work have been proposed in this chapter.

167

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