Pollutant Dispersion in Built Environment

134 Pages·2017·6.745 MB·English

by  Tingzhen Ming, Chong Peng, Tingrui Gong, Zhengtong Li

Tingzhen Ming · Chong Peng
Tingrui Gong · Zhengtong Li
Pollutant
Dispersion
in Built
Environment
Pollutant Dispersion in Built Environment
Tingzhen Ming Chong Peng
(cid:129)
Tingrui Gong Zhengtong Li
(cid:129)
Pollutant Dispersion in Built
Environment
123
Tingzhen Ming Tingrui Gong
Schoolof Civil Engineeringand Schoolof Energy andPower Engineering
Architecture HuazhongUniversity of Science and
WuhanUniversity ofTechnology Technology
Wuhan, Hubei Wuhan, Hubei
China China
ChongPeng Zhengtong Li
Schoolof Architecture andUrban Planning Schoolof Energy andPower Engineering
HuazhongUniversity of Science and HuazhongUniversity of Science and
Technology Technology
Wuhan, Hubei Wuhan, Hubei
China China
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ISBN978-981-10-3820-4 ISBN978-981-10-3821-1 (eBook)
DOI 10.1007/978-981-10-3821-1
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Preface
SincetheseverehazeandfogenvelopedalmostallthemetropolisesofChinainthe
endof2012,thissituationhasbeenbecomingworseandworse.Presently,thehaze
and fog has become a common phenomenon which can be seen from East-North
China through Northern China, Eastern China till Southern China, covering 1–2
millionkm2.Thehazeandfogaremainlyparticulatematterlessthan2.5lminthe
atmospheremainlycomingfromtheemissionsofpowerplants,industrialfactories,
traffic and transportations, and residential sectors. Haze has adverse effects on
human health, especially the early life of children and pregnant mothers. Further,
haze, rich in toxic and hazardous substances, can directly enter the human body
through the respiratory system and adhere to the upper and lower respiratory tract
and lungs, which ultimately causes respiratory and cardiovascular diseases.
Thereby, a further investigation on pollutant dispersion in outdoor built environ-
mentofcities,especiallymetropoliseswithdenselypopulation,plays animportant
role in improving the residents’ thermal comfort and possibly provides the
researchers and decision makers with a good guidance for architecture design,
environmental assessment, energy application, urban planning, and so on.
In this book we are going to reveal the basic mechanisms of fluid flow, heat
transfer, especially the transport of pollutants in outdoor built environment. We
hope this book can be a good guidance for developers who are interested in
building a healthy living environment.
In Chap. 1, we will present a brief introduction of the background of pollutant
and haze in China, and we will also introduce the recent research development of
howtotestandanalyzethepollutantdispersioninbuiltenvironmentduringthepast
20 years.
In Chap. 2, a comprehensive mathematical model including the mass, momen-
tum, and energy equations to describe the fluid flow and heat transfer character-
istics,speciestransportequationtodescribethepollutanttransportmechanism,and
RNGk-eturbulencemodeltoanalyzetheturbulentflowhasbeenputforward.The
numerical simulation results are compared and verified with the existing experi-
mental results. The effects of ambient crosswind velocity and direction, pollutant
v
vi Preface
emission source intensity, the street canyon aspect ratio (building height versus
street width) on the pollutant dispersion are analyzed.
Chapter 3, a numerical simulation was conducted using PHOENICS so as to
assess the wind thermal environment of an urban area according to its current city
structure, architectural composition, materials of ground surface, distribution of
pollution source, environmental conditions, and solar radiation. The thermal envi-
ronment and pollutant transport mechanism were analyzed, so were the problems
and influential characteristics of current city layout.
InChap.4,weextendedtheheattransferfieldsynergyprincipletomasstransfer
fieldsynergy.Withthecomparisonbetweentemperaturegradientandconcentration
gradient, we managed to analyze the synergy angle of velocity with concentration
gradient, based upon which, we also revealed the relationship between synergy
angle and pollutant concentration. Further, via the mass entransy dissipation
derived from the heat transfer function, we analyzed the relationship between that
and pollutant concentration.
In Chap. 5, a novel solar chimney with an inverted U-type cooling tower and a
water spraying system (SCIUCTWSS) was proposed to mitigate the urban air
pollution. In this system, an inverted U-type cooling tower was used to take place
of the traditional chimney erected in the center of the collector; a water spraying
system was installed at the turning point of the inverted U-type cooling tower to
enhance the driving force; a filtration screen is placed near the entrance of the
collectortofilteroutPM2.5andlargeparticulatematterfromtheairflow.Theclean
air out of the system’s outlet can immediately improve the air quality in the
spectrum of human activity. Amathematical model todescribe the fluid flow, heat
transfer of the system was further developed. Influence of injected water from the
water spraying system on the pressure, velocity, temperature, and air density dis-
tributions were analyzed.
This book is supported by the Important Project of National Natural Science
FoundationofChina(No.41590844),theKeyprogramofNationalNaturalScience
Foundation of China (No. 51538004), the National Support Program Sub-topics
of the 12th Five-Year Plan (No. 2011BAJ07B01-1), the National Natural Science
FoundationofChina(51478199),andtheESIDisciplinePromotionFoundationof
WUT (No.35400664).
Addition to the four authors of Professor Chong Peng, Mr. Tingrui Gong, and
Mr.ZhengtongLi,severalcontributorshavehelpedtheauthorstocreatethisbook.
Mr.JieXuhelpedwiththenumericalsimulationsanddraftpreparation.Dr.Liquan
Xu,Mr.CunjinCai,WeiYang,HongwenDou,WeijieFang,JiayueHuang,Wenjie
Deng,YongjiaWu,ZuyuanGuo,Miss.YingziLin,TingLi,andChenZhangmade
contributions to data collection, figures, and tables treatment.They also did lots of
work on tailoring contents, translating, and polishing this book.
Wuhan, China Tingzhen Ming
October 2016
Contents
1 Introduction.... .... .... ..... .... .... .... .... .... ..... .... 1
1.1 Pollutant Dispersion and Haze in Built Environment .. ..... .... 1
1.2 Literature Review.... ..... .... .... .... .... .... ..... .... 2
1.2.1 Experimental Methods and Results.. .... .... ..... .... 2
1.2.2 Numerical Methods and Results .... .... .... ..... .... 5
1.3 Contents of This Book..... .... .... .... .... .... ..... .... 11
References.. .... .... .... ..... .... .... .... .... .... ..... .... 11
2 Heat Transfer and Pollutant Dispersion in Street Canyons.... .... 17
2.1 Introduction .... .... ..... .... .... .... .... .... ..... .... 17
2.2 The Behavior of Pollutant Dispersion.. .... .... .... ..... .... 18
2.3 Mathematical Model.. ..... .... .... .... .... .... ..... .... 21
2.4 Meshing Skills .. .... ..... .... .... .... .... .... ..... .... 27
2.5 Computational Method..... .... .... .... .... .... ..... .... 27
2.6 Verification. .... .... ..... .... .... .... .... .... ..... .... 28
2.7 Results and Discussion..... .... .... .... .... .... ..... .... 29
2.7.1 Comparison of 2D Flow Characteristics .. .... ..... .... 29
2.7.2 Comparison of 3D Flow Characteristics .. .... ..... .... 46
2.8 Conclusions .... .... ..... .... .... .... .... .... ..... .... 53
References.. .... .... .... ..... .... .... .... .... .... ..... .... 54
3 Thermal Comfort and Pollutant Transport in Outdoor Street
Buildings .. .... .... .... ..... .... .... .... .... .... ..... .... 57
3.1 Introduction .... .... ..... .... .... .... .... .... ..... .... 57
3.2 The Description of Model... .... .... .... .... .... ..... .... 58
3.2.1 The Physical Model . .... .... .... .... .... ..... .... 58
3.2.2 Mathematical Model and Numerical Method .. ..... .... 59
3.2.3 Boundary Conditions .... .... .... .... .... ..... .... 61
3.2.4 Simulation Assessment ... .... .... .... .... ..... .... 61
3.3 Block Dimension .... ..... .... .... .... .... .... ..... .... 63
3.3.1 The Wind Thermal Working Conditions in Summer.. .... 63
3.3.2 The Wind Thermal Working Conditions in Winter... .... 67
vii
viii Contents
3.4 Conclusions .... .... ..... .... .... .... .... .... ..... .... 75
References.. .... .... .... ..... .... .... .... .... .... ..... .... 75
4 Filed Synergy Analysis on Pollutant Dispersion in Built
Environment ... .... .... ..... .... .... .... .... .... ..... .... 77
4.1 Introduction .... .... ..... .... .... .... .... .... ..... .... 77
4.2 Field Synergy Principle of Mass Transfer... .... .... ..... .... 79
4.3 Physical and Mathematical Model .... .... .... .... ..... .... 81
4.3.1 Physical Model..... .... .... .... .... .... ..... .... 81
4.3.2 Mathematical Model. .... .... .... .... .... ..... .... 82
4.3.3 Calculation of Solar Radiation . .... .... .... ..... .... 84
4.3.4 Boundary Conditions .... .... .... .... .... ..... .... 85
4.3.5 Meshing Skills ..... .... .... .... .... .... ..... .... 87
4.3.6 The Numerical and Computational Model. .... ..... .... 87
4.4 Results and Discussions .... .... .... .... .... .... ..... .... 88
4.4.1 2D Model Analysis.. .... .... .... .... .... ..... .... 88
4.4.2 3D Model Analysis.. .... .... .... .... .... ..... .... 97
4.5 Conclusions .... .... ..... .... .... .... .... .... ..... .... 108
References.. .... .... .... ..... .... .... .... .... .... ..... .... 108
5 A Solar Chimney with an Inverted U-Type Cooling Tower to
Mitigate Urban Air Pollution... .... .... .... .... .... ..... .... 113
5.1 Introduction .... .... ..... .... .... .... .... .... ..... .... 113
5.2 Model Description ... ..... .... .... .... .... .... ..... .... 114
5.2.1 System Mechanism.. .... .... .... .... .... ..... .... 114
5.2.2 Geometric Model ... .... .... .... .... .... ..... .... 115
5.2.3 Mathematical Model. .... .... .... .... .... ..... .... 116
5.2.4 Boundary Conditions .... .... .... .... .... ..... .... 118
5.2.5 Numerical Method .. .... .... .... .... .... ..... .... 119
5.3 Results and Analysis . ..... .... .... .... .... .... ..... .... 120
5.4 Conclusion. .... .... ..... .... .... .... .... .... ..... .... 124
References.. .... .... .... ..... .... .... .... .... .... ..... .... 125
Index .... .... .... .... .... ..... .... .... .... .... .... ..... .... 127
Chapter 1
Introduction
1.1 Pollutant Dispersion and Haze in Built Environment
There are several problems which arouse worldwide attention: energy crisis,
environmentalpollution,andwaterscarcity.Currently,about90%ofChinesecities
suffer from the severe haze phenomenon which is mainly caused by the emissions
offossil-fired power stations, the exhaust of vehicles, and the dust from numerous
construction sites. Airborne aerosols, such as sulfate, nitrate, ammonium, particu-
lateorganicmatter,blackcarbon,andotherchemicalspecies,canscatterandabsorb
theincidentlightandthereforeleadtoatmosphereopacityandhorizontalvisibility
degrade. When the horizontal visibility is equal to or less than l0 km and atmo-
spheric relative humidity is equal to or less than 90%, this phenomenon is called
atmospheric haze [1]. The basic state policy of urbanization in China helps an
increasingnumberoftheruralpopulationliveinbuildingswithbetterworkingand
living conditions. However, a significant increase of energy consumption during
this urbanization process also causes a great pressure on the Government of P.R.
China as the haze and fog phenomenon is becoming worse and worse. Haze has
adverse effects on human health, especially the early life of children and pregnant
mothers[2–7].Haze, rich intoxic andhazardous substances, can directlyenter the
human body through the respiratory system and adhere to the upper and lower
respiratory tract and lungs, which ultimately causes respiratory and cardiovascular
diseases [8].
In high-density megacities, such as Beijing, Shanghai, Hong Kong, etc., air
pollution has higher impact on the public health than those of lower population
density. Presently, various adverse impacts of air pollution and haze on human
activitieshavebeenwitnessed,whichhascausedunaccountablelossanddamages.
Apartfromhigherpollutionemissionsduetohumanactivitiesindenselypopulated
street canyons, stagnated airflow due to closely packed tall buildings means lower
dispersion potential. High-density urban morphologies need to be carefully
designed to lessen the ill effects of high-density urban living [9]. In addition, the
©ZhejiangUniversityPressandSpringerScience+BusinessMediaSingapore2017 1
T.Mingetal.,PollutantDispersioninBuiltEnvironment,
DOI10.1007/978-981-10-3821-1_1
2 1 Introduction
researchdatashowedthat,in2010,theresidentialsectoraccountedforaround18%
of total energy consumption in China, but contributed 10, 50, and 69% of
anthropogenicSO ,black carbon,andorganiccarbonemissions,respectively[10].
2
1.2 Literature Review
The research on air pollution and it transport mechanism in built environment has
attract worldwide attention. The research group led by Prof. Zhaolin Gu presented
excellent work in the fields of transportation mechanism of particles such as sand
and dust in the environment [11–21], the effect of green plants on air quality [22],
theeffectofairqualityonurbandesign[23,24],andnumericalsimulationmethod
of particles in various ambience [16, 19, 24–27]. The research group led by Prof.
Yinping Zhang comprehensively considered seriously the volatile organic com-
pounds (VOCs) emissions, their adverse effect on residents, the measurement
methods,andthetreatmentmethodinindoorenvironment[7,28–41].Theresearch
group led by Prof. Qihong Deng mainly considered the effects of various particles
on children and pregnant mothers’ health [3–7, 42–53]. In addition, quite a lot of
researchers focused on the pollutant dispersion in street canyons as transport
emissions are regarded as a main contribution in air pollution of metropolis.
1.2.1 Experimental Methods and Results
In 2002, Sagrado et al. [54] experimentally studied the pollutant dispersion in a
two-dimensional street canyon in the L-2B wind tunnel at von Karman Institute in
which they mainly considered the influence of the height of the downstream
building. In their research, the pollutant source was situated in the middle of the
street. The concentration measurements were performed by means of light scat-
tering technique and the velocity field was measured with particle image
velocimetry(PIV).Twodifferentsetsofconfigurationsweredefined:opencountry
and non-isolated street canyon. In the open country cases, only the street canyon
wasstudiedwithoutanyotherbuildingsaround.Inthenon-isolatedstreetcanyona
third building was placed upstream of the street to study its influence on the flow
anddispersioninthestreet.Inboth setsofconfigurationsthree different heightsof
the downstream building were investigated. From the measurements it was found
that increasing the height of the downstream building decreases the pollutant
concentration in the street. In both cases, open country and non-isolated street, the
flow is drastically separated and accelerated when impacting against the first
building placed upstream.
Rotach et al. [55] reported the first results of an urban tracer experiment being
realized in the framework of the “Basel Urban Boundary Layer Experiment” in an
areawithabundantinformationonturbulenceandflowconditionsavailable.Inthis