the second iasted international conference on environmental

8/14/2019 The Second IASTED International Conference on Environmental

1/19

COAGULATION AND ATMOSPHERIC

DISPERSION OF POLYDISPERSE

AEROSOLS

Ana T. Celada Murillo

Alejandro Salcido Gonzlez

Instituto de Investigaciones Elctricas, Mxico

The Second IASTED International Conference on Environmental Modelling and Simulation 2006

November 2006


2/19

Transport

Dispersion

Chemical reactions

Condensation / evaporation

Nucleation

Coagulation

Gravitational sedimentation

The study of environmental impacts of atmospheric aerosols

(damages to the human health, climate changes, degradation ofvisibility, acid rain precursors , etc).


3/19

Coagulation

Union of two aerosol particles after a collision

between them

November 2006

Accumulation mode

(0.100 - 1 m)

Nuclei mode

(0.001 0.100 m)


4/19

Motivation

Transport and dispersion are

modeled with the gaussian

model or with Reynolds

average of mass balance

equation.

These models do not reflect the

fluctuating and random nature of

turbulent dispersion,

Smooth space-time

concentration distributions

November 2006


5/19

Some models of transport and

dispersion of aerosols dontinclude the coagulation process

in their estimations

Concentration of smallestaerosol particles is

overestimated

Polydisperse coagulation istwice more rapid than

monodisperse.

Mistakes in the estimationsof number concentrations

Smoluchowsky's theory describes

the coagulation process with

monomers.

November 2006

Motivation


6/19

Coagulation and dispersion model of polydisperse

aerosols

++= R

s

s RRR

dVtrdVtQdAtdVtdt

d),()(),(),(),( xxxxnxJx

=iC

i dVtFV

tF ),(1

),( xr

Lx

LzLy


7/19

),(),(),(),(),( trtQttdt

di

s

issii rrxxrr ++=

+++=+ ),(),(),(),(),(),( trtQttttt is issiii rrxxrrr

Aerosol Production Model by

coagulation

Particle Flux

Model

= iCi dAtVt nxJr ),(

1

),( = iCi dVtrVtr ),(1

),(xr
http://modelocoag1.ppt/http://modelocoag1.ppt/http://modelocoag1.ppt/http://modelocoag1.ppt/


8/19

Initially monodisperse

aerosol

Smoluchowsky Theory Spheric particles

All collisions coagulation

Binary collisions

Volume and mass are

conserved in each collision.

MFC model

Polidisperse aerosol

Aerosol Production model by Coagulation

0

200

400

600

800

1000

1200

Ni

I n t e r v a l o d e d i m e t r o s

nk(#/cm

3)

1 2 3 4 5 6

k

0

200

400

600

800

1000

1200

Ni

I n t e r v a l o d e d i m e t r o s

nk(#/cm

3)

1 2 3 4 5 61 2 3 4 5 6

kk


9/19

A particle in the interval will be formed depending

on three factors:

K

P

Q

The probability of one collision happens

in the system

The probability that the collision

happens between particles of theintervals and

Collision result will be a new

particle in the interval

=

Aerosol production model by coagulation
http://pij.ppt/http://pij.ppt/http://pij.ppt/http://pij.ppt/http://pij.ppt/http://pij.ppt/http://pij.ppt/http://pij.ppt/http://qijk.ppt/http://qijk.ppt/http://qijk.ppt/http://qijk.ppt/http://qijk.ppt/http://qijk.ppt/http://qijk.ppt/http://qijk.ppt/http://qijk.ppt/http://qijk.ppt/http://qijk.ppt/http://qijk.ppt/http://qijk.ppt/http://qijk.ppt/http://pij.ppt/http://pij.ppt/http://pij.ppt/


10/19

Aerosol production model by coagulation

=

= 1, )1(21

),(i

i QPQPtrr


11/19

Particle Flux Model

ri

),(),(),( ttt ioutput

i

input

i rrr =

Lx

LzLy

++=z

iz

y

iy

x

ix

ii

output

L

tv

L

tv

L

tvtt ),(),(),(),(),( rrrrr


12/19

e1e2

e3

riri - e1Lx ri + e1Lx

ri + e3Lz

ri - e3Lz

[ ]{[ ]}),(),(),(

1

2

tvtvt

Lkkkkkk

k

i

qqq ++=

),(),(),(1

),(

3

1 tvtvtt

kkkkk

input pppr +=

kkikkkik LL erqerp +==

Lx

Lz

Ly

Particle Flux Model


13/19

Aerosol Dispersion Model

),(),(),( trwtrutrv iii +=


14/19

Simulation results Coagulation and Dispersion Model

General characteristics of emission source [Buckholtz,

1980]

Emission velocity:

Stack diameter:

Stack height:

Effluent temperature:

Effective height of the

plume:

Air temperature:

Atmospheric pressure:Mean wind speed:

Cloudiness:

Atmospheric stability:

Aerosol:Density:

Diameter interval:

16.76 m/s

8.23 m

76.20 m

393.15 K

483 m

283.15 K

1 atm2.10 m/s

Sunny day without clouds

A class (Pasquill)

Aluminosilicates2.40 g cm-3

0.01-64.44 m

1.E+00

1.E+02

1.E+04

1.E+06

1.E+08

1.E+10

0.01 0.1 1 10 100

Diameter (m)

Num

berdensity

(#cm-3)


15/19

0 1000 2000 3000 4000

Time (s)

0x100

4x107

8x107

1x108

2x108

Nu

mberdensity(#

cm-3)

Mean diameter 0.01 m

0 1000 2000 3000 4000

Time (s)

0x100

4x107

8x107

1x108

2x108

Nu

mberdensity(#

cm-3)


With emission, dispersion and coagulation

With emission and dispersion

0 1000 2000 3000 4000

Time (s)

0x100

1x106

2x106

3x106

4x106

Numberdensity(#cm-3)



16/19

X=80 m

0.0E+00

3.0E+06

6.0E+06

9.0E+06

1.2E+07

-800 -400 0 400 800

Distance Z direction, (m)

Numberde

nsity(#cm

-3)

X=320 m

0.0E+00

4.0E+06

8.0E+06

1.2E+07

1.6E+07

2.0E+07

-800 -400 0 400 800

Numberdensity

(#cm

-3) n1 - 0.010 m

n2 - 0.030 m

n3 - 0.060 m

n4 - 0.120 m


17/19

0.0E+00

2.5E+05

5.0E+05

7.5E+05

-800 -400 0 400 800

Distance Z direction, (m)

N

umberdensity

(#cm

-3)

n1 - 0.010 m

n2 - 0.030 m

n3 - 0.060 m

n4 - 0.120 m

X=3840 m

CONCLUSIONS


18/19

CONCLUSIONS

Simulation results showed the coagulation as the main mechanism inthe consumption of the nuclei particles (diameters between 0.01 and

0.12 m) near of the source.

The coagulation produces accumulation of the particles with mean

diameters between 0.12 and 0.96 m.

Qualitatively, these results are in agreement with the observed onesby Zhu et al. in relation with aerosols of traffic emissions in two

highways at California.

Coagulation is an important mechanism in the transfer of the finest

aerosol particles.

REFERENCES


19/19

REFERENCES

http://rmf.fciencias.unam.mx/pdf/rmf/51/4/51_4_379.pdf

http://rmf.fciencias.unam.mx/pdf/rmf/54/6/54_6_422.pdf

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