Aerosol, Fluid ,,Dispersion of Pollutants Introduced into the Atmosphere as Determined by Residence Times
(Husar and Patterson, 1980)
After formation, the aerosols are mixed and transported by atmospheric motions and are primarily removed by cloud and precipitation processes.
Aerosol formation at source:
Primary aerosol formation: Product of incomplete combustion
Elemental carbon
Organic carbo
An important assumption of Stokes’s law is the relative velocity of gas right at the surface of the sphere is zero. The assumption is not met for small particles whose size approaches the mean free path of the gas such particles settle faster than predicted by stokes law because there is a slip at the surface of the particle. At standard conditions, this error become significant for particles less than 1 mm in diameter.
In 1910 Cunningham derived a correction factor for Stokes’s law to account for effect of slip.
I Hope You all like it very much. I wish it is beneficial for all of you and you can get enough knowledge from it. Clear and appropriate objectives, in terms of what the audience ought to feel, think, and do as a result of seeing the presentation. Objectives are realistic – and may be intermediate parts of a wider plan.
AIR POLLUTION CONTROL course material by Prof S S JAHAGIRDAR,NKOCET,SOLAPUR for BE (CIVIL ) students of Solapur university. Content will be also useful for SHIVAJI and PUNE university students
Es air pollutions
1. Air Pollutions
2. Presentation outline • Introduction • Structure of Atmosphere • Definition of Air Pollution • Source of Air Pollution • Classification of Air Pollution • Effect of Air Pollution • Control of Air Pollution
I Hope You all like it very much. I wish it is beneficial for all of you and you can get enough knowledge from it. Clear and appropriate objectives, in terms of what the audience ought to feel, think, and do as a result of seeing the presentation. Objectives are realistic – and may be intermediate parts of a wider plan.
AIR POLLUTION CONTROL course material by Prof S S JAHAGIRDAR,NKOCET,SOLAPUR for BE (CIVIL ) students of Solapur university. Content will be also useful for SHIVAJI and PUNE university students
Es air pollutions
1. Air Pollutions
2. Presentation outline • Introduction • Structure of Atmosphere • Definition of Air Pollution • Source of Air Pollution • Classification of Air Pollution • Effect of Air Pollution • Control of Air Pollution
NUMERICAL SIMULATIONS OF HEAT AND MASS TRANSFER IN CONDENSING HEAT EXCHANGERS...ssuser7dcef0
Power plants release a large amount of water vapor into the
atmosphere through the stack. The flue gas can be a potential
source for obtaining much needed cooling water for a power
plant. If a power plant could recover and reuse a portion of this
moisture, it could reduce its total cooling water intake
requirement. One of the most practical way to recover water
from flue gas is to use a condensing heat exchanger. The power
plant could also recover latent heat due to condensation as well
as sensible heat due to lowering the flue gas exit temperature.
Additionally, harmful acids released from the stack can be
reduced in a condensing heat exchanger by acid condensation. reduced in a condensing heat exchanger by acid condensation.
Condensation of vapors in flue gas is a complicated
phenomenon since heat and mass transfer of water vapor and
various acids simultaneously occur in the presence of noncondensable
gases such as nitrogen and oxygen. Design of a
condenser depends on the knowledge and understanding of the
heat and mass transfer processes. A computer program for
numerical simulations of water (H2O) and sulfuric acid (H2SO4)
condensation in a flue gas condensing heat exchanger was
developed using MATLAB. Governing equations based on
mass and energy balances for the system were derived to
predict variables such as flue gas exit temperature, cooling
water outlet temperature, mole fraction and condensation rates
of water and sulfuric acid vapors. The equations were solved
using an iterative solution technique with calculations of heat
and mass transfer coefficients and physical properties.
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
HEAP SORT ILLUSTRATED WITH HEAPIFY, BUILD HEAP FOR DYNAMIC ARRAYS.
Heap sort is a comparison-based sorting technique based on Binary Heap data structure. It is similar to the selection sort where we first find the minimum element and place the minimum element at the beginning. Repeat the same process for the remaining elements.
Online aptitude test management system project report.pdfKamal Acharya
The purpose of on-line aptitude test system is to take online test in an efficient manner and no time wasting for checking the paper. The main objective of on-line aptitude test system is to efficiently evaluate the candidate thoroughly through a fully automated system that not only saves lot of time but also gives fast results. For students they give papers according to their convenience and time and there is no need of using extra thing like paper, pen etc. This can be used in educational institutions as well as in corporate world. Can be used anywhere any time as it is a web based application (user Location doesn’t matter). No restriction that examiner has to be present when the candidate takes the test.
Every time when lecturers/professors need to conduct examinations they have to sit down think about the questions and then create a whole new set of questions for each and every exam. In some cases the professor may want to give an open book online exam that is the student can take the exam any time anywhere, but the student might have to answer the questions in a limited time period. The professor may want to change the sequence of questions for every student. The problem that a student has is whenever a date for the exam is declared the student has to take it and there is no way he can take it at some other time. This project will create an interface for the examiner to create and store questions in a repository. It will also create an interface for the student to take examinations at his convenience and the questions and/or exams may be timed. Thereby creating an application which can be used by examiners and examinee’s simultaneously.
Examination System is very useful for Teachers/Professors. As in the teaching profession, you are responsible for writing question papers. In the conventional method, you write the question paper on paper, keep question papers separate from answers and all this information you have to keep in a locker to avoid unauthorized access. Using the Examination System you can create a question paper and everything will be written to a single exam file in encrypted format. You can set the General and Administrator password to avoid unauthorized access to your question paper. Every time you start the examination, the program shuffles all the questions and selects them randomly from the database, which reduces the chances of memorizing the questions.
Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
The presentation also covers the positive and negative aspects of inductive bias, along with strategies for mitigating potential drawbacks. We'll explore examples of how bias manifests in algorithms like neural networks and decision trees.
By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
2. Outline
What is aerosol?
Life time and transport of aerosol
compared to gases.
How do aerosol look like?
Why do we bother about these tiny
particles?
Aerosol formation?
Aerosol size and shape
Forces on Aerosol
3. Suspended particles in
medium
Type of suspended particles
Suspending
medium
gas Liquid solid
Gas - Fog, mist, spray Fume, dust
Liquid Foam Emulsion Colloid, suspension,
slurry
Solid sponge Gel Alloy
5. Residence time and transport of
aerosol
Dispersion of
Pollutants Introduced
into the Atmosphere
as Determined by
Residence Times
(Husar and Patterson,
1980)
After formation, the
aerosols are mixed
and transported by
atmospheric motions
and are primarily
removed by cloud and
precipitation
processes.
6. Size and Shape of Aerosol
• Size range: 0.001 mm (molecular cluster) to
100 mm (small raindrop)
Fly ash particle
from coal burning
Granite cutting
particle
Iron oxide
particles
7. 0.01 0.1 1.0 10.0
- « nucleation: radius is between
0.002 and 0.05 mm. They result
from combustion processes, photo-
chemical reactions, etc.
- « accumulation: radius is
between 0.05 mm and 0.5 mm.
Coagulation processes.
-« fine: particles (nucleation and
accumulation) result from
anthropogenic activities,
- « coarse: larger than 1 mm. From
mechanical processes like aeolian
erosion.
Aerosol Size Distribution
8.
9. Visibility Degradation from Aerosols
7.6 µgm-3
12.0 µgm-3
21.7 µgm-3 65.3 µgm-3
Glacier National Park, Montana
11. Aerosol and climate change
Cloud with
aerosol
Numerous
cloud nuclei
Small droplets,
Brighter cloud,
less prone to
rain
Annual mean precipitation (1976-2003)
minus (1948-1975): Green/blue (red/Yellow)
decrease (increase)
Drought
Radiative Forcing (Wm-2) due to aerosol
Top of the Atmosphere
(+ve forcing)
Surface (-Ve forcing)
Knowledge gap: Large uncertainty
in quantification of impact of
aerosol on climate [IPCC, 2007].
12. Ship Track Formation – the First
Evidence of Aerosol Indirect Effect
N ~ 40 cm-3
W ~ 0.30 g m-3
re ~ 11.2 µm
N ~ 100 cm-3
W ~ 0.75 g m-3
re ~ 10.5 µm
“Borrowed” from Michael King
13. • Adding CCN makes clouds with more, smaller droplets.
• These clouds are whiter, reflect more sunlight net
cooling
Aerosol-indirect climate effect Ship
tracks off the Washington coast
14. Formation of aerosol
• Aerosol formation at source:
– Primary aerosol formation: Product of
incomplete combustion
• Elemental carbon
• Organic carbon
Elemental cabon
Organic cabon
EC+OC
15. Formation of aerosol-2
• Aerosols smaller than 1 µm are mostly formed
by condensation processes such as conversion of
sulfur dioxide (SO2) gas (released from volcanic
eruptions) to sulfate particles and by formation of
soot and smoke during burning processes.
• Aerosol particles larger than about 1 mm in size
are produced by windblown dust and sea salt
from sea spray and bursting bubbles
16. Secondary aerosol formation
in the Atmospher
Soil dust
Sea salt
Environmental importance: health (respiration), visibility, climate,
cloud formation, heterogeneous reactions, long-range transport of nutrients…
17. • Can you name the laws of motion for a
moving object?
– Newton’s law
– stokes law
18. Do aerosol follow Newton’s
law?
• Newton’s law
– Inertial force dominates the viscous force
• What is Reynolds number?
• Re>1000
– Large body such as cannonballs (not for particles)
– http://csep10.phys.utk.edu/astr161/lect/history/newton3laws.ht
ml
19. Stokes’s Law
– Viscosity dominates
over Inertia
– http://members.shaw.c
a/gp.lagasse/Centrifug
e%20Training/basic2.ht
ml
– Solution of Navier-
Stokes equations
(differential eqs
describing the fluid
motion)
Navier-Stokes equations are
derived from application of
Newton’s second law to a fluid
element on which the forces
include body forces, pressure, and
viscous forces.
20. Stoke’s Law: Assumptions for solving
Navier-Stoke equtions
• Resulting equations are very difficult to solve because they are nonlinear partial
differential equations.
• Therefore, Stoke’s solution involved the assumptions
– Inertial force is negligible compared to viscous force: this eliminates the higher
order terms in Navier-Stokes equation and yield linear equation that can be
solved.
– Fluid is incompressible.
– There are no wall or other particles nearby
– The motion of the particle is constant
– The particle is rigid sphere
– The fluid velocity at the particle surface is zero.
The net force acting on the particle is obtained by integrating the normal and
tangential forces over the surface of the particle.
Re<1.0 (error in the drag force will be 12% error at Re=1.0 and 5% error at Re=0.3)
21. Stokes’s law: Assumptions
valid or invalid
• Fluid is incompressible
– Air around the particle can not be compressed
significantly when particle moves through it. Valid
– Presence of the wall within 10 diameters of
particle will modify the drag coefficient . Aerosols
are of small size therefore only a tiny fraction of
aerosol will be within 10 particle diameters in any
real container or tube. Valid
22. Stokes Law: Non-rigid particle
– What if it is water droplet (non rigid sphere)?
• Settle 0.6% faster than predicted
• Reason circulation develop within the droplet caused
by resisting force at drop let surface
23.
24. Aerosol settling by gravity
• Drag force (FD) = Inertial force (FG=mg)
pg
For water droplet
settling in air
Not valid for particles
less than 1.0 mm size.
25. Aerosol settling by gravity
…contd.
• 10% accurate for particle with standard
density having diameter of 1.5-75 mm.
• Mechanical mobility of particle (for d>1.0 mm)
– Ratio of terminal velocity of particle to the steady
force producing that velocity.
26. • Example 1: What are the terminal velocity
drag force and mobility of a 2.5 mm diameter
iron-oxide sphere settling in still air? The
density of iron oxide is 5200 kg/m3.
η=1.81X10-5
27. • An important assumption of Stokes’s law is the
relative velocity of gas right at the surface of the
sphere is zero. The assumption is not met for
small particles whose size approaches the mean
free path of the gas such particles settle faster
than predicted by stokes law because there is a
slip at the surface of the particle. At standard
conditions, this error become significant for
particles less than 1 mm in diameter.
• In 1910 Cunningham derived a correction factor
for Stokes’s law to account for effect of slip.
What about Particles 0.1 mm
to 1.0 mm diameter?
28. What about Particles 0.1 mm
to 1.0 mm diameter?
Particle dp<1.0 mm
Particle dp>1.0 mm
Include slip correction factor
or Cunningham correction
factor (Cc)
l= Mean free path (For
air at 1 atm 0.066 mm)
Slip correction factors for particles 1.0 mm size is 1.15 that means
the particle settles 15% faster than predicted by stokes equ
29. Particles less than 0.1 mm
diameter
• For particle less than 0.1 mm
• Settling velocity (V): When Re<1.0
31. Nonspherical Aerosol
• Liquid droplets less than 1 mm
and some solid particle are
spherical. Most other type of
particles are non spherical.
• Some have regular geometric
shapes, such as cubic (sea salt
particles), cylindrical (bacteria
and fibers).
• Agglomerated particles,
crushed material have
irregular shape.
• Dynamic shape factor (α) is
applied to Stoke’s Law to
account for effect of shape on
particle motion.
α is the ratio of actual
resistance force of the
nonspherical particle to the
resistance force of sphere
having the same volume
and velocity as
nonspherical particle.
de = equivalent volume
diameter
33. When particle is travelling
in accelerated field
• This is important for understanding the collection
mechanism of aerosols. Such as cascade
impactor.
• Relaxation time and stopping distance are
important
• Relaxation time characterizes the time required
by the particle to adjust or relax its velocity to
anew condition of force.
• Relaxation time (τ) = mass X mobility=mB
34. Stopping Distance
• Maximum distance a particle with an initial
velocity V0 will travel in still air in the absence of
external force.
– S= V0*τ
• Velocity of the particle at any time t in
accelerating field
– V(t)=Vf-(Vf-V0)e-t/τ
– For the particle released in still air and accelerating to its
terminal velocity Vf is settling velocity.
How long will it take a 30 mm glass sphere (p =
2500 kg/m3) to reach a velocity equal to 50%
of settling velocity if it is released from rest in
still air.
35. Thermal and radiometric forces
• When the temperature gradient is established in a
gas, an aerosol particle in that gas experience a
force in the direction of decreasing temperature. The
movement of the particle that results from this force
is called thermophoresis.
• The magnitude of the thermal force depends on gas
and particle properties, as well as temperature
gradient.
• Thermal precipitators are used for aerosol collection.
Example in real life: heated metal rod
immersed in smoke.
The aerosol move away from the rod
37. Radiometry force
• Photophoresis is a special case of
thermophoresis in which the absorption of
light by particle creates a temperature
gradient in the particle. The gas immediately
around the particle takes on the same
gradient and establishes the radiometric force.
•
38. References
• Hinds, W. C. (1999) Aerosol Technology:
Properties, Behavior, and measurement of air
born particles. John Willey & Sons Inc.
• Friedlander S. K. (2000) Smoke, dust, and haze:
fundamentals of aerosol dynamics. Oxford
University Press.