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- 2. Particle size Simplest case: a spherical, solid, single component particle Critical dimension: radius or diameter Next
- 3. Particle size from image analysis Optical and electron microscopes give 2-D projected images of particles (3-D
- 4. “The Radius of Gyration of an Area about a given axis is a distance k from
- 5. Diameters can vary, exercise
- 6. Particle size- equivalent diameters Other equivalent diameters can be defined: Sieve equivalent diameter – diameter equal
- 7. More diameters Volume diameter – diameter of sphere having same volume Obtained from Coulter counter techniques
- 9. Concept of fractal dimension Aerosol particles which consist of agglomerates of ‘primary particles’, (often, combustion generated)
- 10. Fractal dimension Fractals - Df = 2 = uniform density in a plane, Df of 3
- 11. Particle Size Con’t Particle concentration – suspensions in air Particle density – powders What if particles
- 12. Particle concentration Again, many different ways to describe concentration Low concentrations of suspended particles: usually number,
- 13. Mass and Volume Concentrations Mass concentration: particle mass per unit volume of gas Volume concentration: particle
- 14. Particle concentrations - powders Additional definitions necessary: Bed or bulk density = mass of particles in
- 15. What if we have a mixture of particles of different sizes? In the real world, this
- 16. Example histogram: Can also create histogram from raw particle size data using Analysis tool pack add-in,
- 17. Continuous particle size distributions More useful: continuous distributions, where some function, nd, describes the number of
- 18. More continuous size distributions M is total mass of particles per unit volume at a given
- 19. What do they look like?
- 20. Frequency distributions Cumulative frequency distribution: FN = fraction of number of particles with diameter (Fv for
- 21. Example of cumulative frequency distribution from discrete data Example of differential frequency distribution in Fig. 3.3
- 22. More on size distributions In measuring size distributions, instruments such as impactors give mass of particles
- 23. Spreadsheet tricks
- 24. Number, mass, surface area distributions not the same! Mass distribution from before Using arithmetic average of
- 25. Describing distributions using a single number, a.k.a. what is average? General formula for the mean, x,
- 26. Standard shapes of distributions Normal Log normal Bimodal
- 27. Similarity transformation The similarity transformation for the particle size distribution is based on the assumption that
- 28. Self-preserving size distribution For simplest case: no material added or lost from the system, V is
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