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Questions and Answers
What is the mass efficiency for collecting large particles using the collector?
What is the mass efficiency for collecting large particles using the collector?
Given the efficiencies of the collector, which size of particles contributes the least to the overall weight percent efficiency?
Given the efficiencies of the collector, which size of particles contributes the least to the overall weight percent efficiency?
What is the overall weight percent efficiency of the collector based on the given information?
What is the overall weight percent efficiency of the collector based on the given information?
Which of the following correctly describes the relationship between mass fraction and collection efficiency for the medium particles?
Which of the following correctly describes the relationship between mass fraction and collection efficiency for the medium particles?
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What factor affects the overall efficiency of the collector the most?
What factor affects the overall efficiency of the collector the most?
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What is the outgoing amount of the large-sized particles based on the provided data?
What is the outgoing amount of the large-sized particles based on the provided data?
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How is the overall efficiency, denoted as η, defined in the context provided?
How is the overall efficiency, denoted as η, defined in the context provided?
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What is the total penetration value calculated from the given data?
What is the total penetration value calculated from the given data?
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When calculating total penetration using penetration values of different size ranges, which formula is correct?
When calculating total penetration using penetration values of different size ranges, which formula is correct?
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If the efficiency η is known for multiple size ranges, how can the overall collection efficiency be predicted?
If the efficiency η is known for multiple size ranges, how can the overall collection efficiency be predicted?
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In a continuous particle size distribution, what happens to the discrete PSD as the size range becomes very small?
In a continuous particle size distribution, what happens to the discrete PSD as the size range becomes very small?
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What type of distribution is commonly used for the size distribution of particulate matter in aerosol science?
What type of distribution is commonly used for the size distribution of particulate matter in aerosol science?
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For which size range is the frequency (fi) highest based on the provided data?
For which size range is the frequency (fi) highest based on the provided data?
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What value corresponds to the size range of 20-35?
What value corresponds to the size range of 20-35?
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What does the variable 'p' represent in the equation for continuous particle size distribution?
What does the variable 'p' represent in the equation for continuous particle size distribution?
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At what particle size range does the frequency drop to its lowest according to the data?
At what particle size range does the frequency drop to its lowest according to the data?
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What is the significance of making Δd approach zero in the context of particle size distribution?
What is the significance of making Δd approach zero in the context of particle size distribution?
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Which of the following size ranges has a frequency value closest to zero?
Which of the following size ranges has a frequency value closest to zero?
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What is the definition of PM (Particulate Matter)?
What is the definition of PM (Particulate Matter)?
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Which of the following best describes 'Soot'?
Which of the following best describes 'Soot'?
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Which of the following describes 'Mist' in terms of particulate matter?
Which of the following describes 'Mist' in terms of particulate matter?
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What is the primary characteristic of 'Fly Ash'?
What is the primary characteristic of 'Fly Ash'?
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Which mechanism of particle collection involves the collision of particles with a larger surface?
Which mechanism of particle collection involves the collision of particles with a larger surface?
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What role does Stokes Law play in understanding particulate matter?
What role does Stokes Law play in understanding particulate matter?
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Which of the following is NOT a common process for particulate pollutant formation?
Which of the following is NOT a common process for particulate pollutant formation?
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What characteristic differentiates 'Fume' from other particulate pollutants?
What characteristic differentiates 'Fume' from other particulate pollutants?
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What happens to Stokes' law when the flow becomes turbulent?
What happens to Stokes' law when the flow becomes turbulent?
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What is the condition for laminar flow according to Reynolds number?
What is the condition for laminar flow according to Reynolds number?
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How is Reynolds number defined?
How is Reynolds number defined?
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Which range of Reynolds number indicates that flow is becoming turbulent?
Which range of Reynolds number indicates that flow is becoming turbulent?
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Under what condition does Stokes' law work satisfactorily?
Under what condition does Stokes' law work satisfactorily?
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What does a higher Reynolds number indicate?
What does a higher Reynolds number indicate?
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If the Reynolds number is equal to 1000, what can be inferred about the flow?
If the Reynolds number is equal to 1000, what can be inferred about the flow?
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What is the significance of the term $ rac{D V
ho_{fluid}}{
u}$ in defining Reynolds number?
What is the significance of the term $ rac{D V ho_{fluid}}{ u}$ in defining Reynolds number?
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What does the geometric mean diameter (Dmean, g) represent in a particle size distribution?
What does the geometric mean diameter (Dmean, g) represent in a particle size distribution?
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How is the arithmetic mean diameter (Dmean) calculated?
How is the arithmetic mean diameter (Dmean) calculated?
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What is the role of the standard deviation (σ) in particle size distributions?
What is the role of the standard deviation (σ) in particle size distributions?
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Which formula represents the calculation of Dmean, g using logarithmic means?
Which formula represents the calculation of Dmean, g using logarithmic means?
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What does a cumulative fraction of 50% indicate regarding particle size?
What does a cumulative fraction of 50% indicate regarding particle size?
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In terms of particle classification, how is Dmean distinct from Dmean, g?
In terms of particle classification, how is Dmean distinct from Dmean, g?
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Which of the following correctly describes the relationship between Dmean and Dmean, g?
Which of the following correctly describes the relationship between Dmean and Dmean, g?
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What does the term 'D' represent in the context of particle size distribution calculations?
What does the term 'D' represent in the context of particle size distribution calculations?
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Study Notes
Air Pollution Control Engineering - Week 9
- Particulate Matters (PM): A collection of solid and liquid particles suspended in the air, many are hazardous.
- Common PM Pollutants: Dust, fly ash, fume, mist, smoke, particle, fog, soot. Each with distinct characteristics.
- Formation of PM Pollutions: PMs can be formed through condensation processes (atmospheric reactions, combustion), accumulation processes (combustion, coagulation on existing particles, atmospheric reactions), and mechanical processes (wind blown dust, emissions, sea spray, volcanoes, and plant emissions).
- Particle Size Distribution: Particles exist in a range of sizes, this distribution is crucial in determining collection efficiency in control devices and impacts on human health. Sizes are typically categorized in log-normal distributions.
- Efficiency of Particle Collection: Mechanisms differ greatly with particle size. Control device efficiency directly correlates to particle size. Collection mechanisms include inertia impaction, interception, diffusion.
- Particle Size Categories (EPA Classifications): Categorisation of PM based on diameter: total suspended particulate matter (TSP), PM10, PM2.5, particles less than 0.1 µm, condensable particulate matter.
- Particle Shape and Density: These factors greatly affect the way particles behave in the air and are crucial when evaluating particle collection mechanisms.
- Forces Acting on Particles: Essential forces include buoyancy, gravity, drag. These forces combine to influence particle settling velocity.
- Stokes Law: Describes terminal settling velocity for particles under laminar flow. Includes density of particle and air, particle diameter, and fluid viscosity/gravity
- Particulate Size Distribution: Important for efficiency of collection mechanisms. Different particle size ranges means different collection methods.
- Aerodynamic Diameter vs. Stokes Diameter: Importance of aerodynamic diameter relates to collection efficiency. Stokes diameter also crucial, but more complicated.
- Standard Deviation: Measures the spread/consistency in particle size, critical for understanding and evaluating treatment methods.
- Cunningham Correction Factor: Accounts for deviations from the continuous fluid assumption when particle size is small.
- Mechanisms for PM Collection: Methods including gravity settlers, cyclones, electrostatic precipitators (ESPs), fabric filters, and scrubbers. Specific roles of each type and how they work.
- Examples illustrate ways to calculate overall efficiency, and the impact of various types of parameters.
- How to Control PM: Methods involve bringing particles into contact with each other to coalesce, and grow in size (often using water). These coalesced materials are often sent to a landfill. Collection mechanisms also vary.
- Collection Mechanisms, Inertial Impaction: Particles are impacted by moving structures.
- Collection Mechanisms, Interception: Particles are collected by structures due to their shape rather than inertial forces.
- Collection Mechanisms, Brownian Diffusion: Small particles are deflected from their path due to bombardment by gas molecules.
(II) Forces Acting on Particles & Stokes Law
- Forces Acting on Particles in a Fluid
- Drag Force / Stokes Law
- Terminal Settling Velocity
- Assumptions for Stokes' Law (continuous fluid, laminar flow, Newton's law of viscosity)
- Why Settling Velocity is Important in controlling air pollution.
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Description
This quiz covers key concepts related to particulate matter (PM) in air pollution control, including common pollutants, formation processes, and particle size distributions. Understanding the efficiency of particle collection devices is crucial for managing air quality and protecting human health.
