1. Session 7 Particle Size Distributions
Fall 2008
By Wen-Whai Li
Particle Size Distributions

2. Determining the Terminal Velocity
Fall 2008
By Wen-Whai Li
Particle Size Distributions

3. Determining the Terminal Velocity
Fall 2008
By Wen-Whai Li
Particle Size Distributions

4. Particle Size Distributions
Characteristics:
Wide range in size: 5 orders of magnitude 1 nm – 100 µm
Wide range in shape: particles come in all shapes
Wide range in numbers: in nanometers and in micrometers
Variable density and aerodynamic properties
Any of the properties, such as number, mass, size, surface area, etc, may have various adverse health effects
Fall 2008
By Wen-Whai Li
Particle Size Distributions

5. Particle Size Distributions
Fall 2008
By Wen-Whai Li
Particle Size Distributions

6. Particle Size Distributions
Fall 2008
By Wen-Whai Li
Particle Size Distributions

7. Particle Size Distributions
Fall 2008
By Wen-Whai Li
Particle Size Distributions

8. Particle Size Distributions
Fall 2008
By Wen-Whai Li
Particle Size Distributions

9. Particle Size Distributions
Fall 2008
By Wen-Whai Li
Particle Size Distributions

10. Mode, Median, and Mean of Aerosol Size
Mode: the diameter of the most frequent size
Median: The diameter for which ½ of the total number of particles are smaller and ½ are larger
Arithmetic Mean: The sum of all particle sizes divided by the total number of particles
In general, Mode < Median < Mean
Geometric Mean: the logarithm of the
arithmetic mean of the logarithmic
of all values or the nth root of
product of the N values
Fall 2008
By Wen-Whai Li
Particle Size Distributions

11. Mode, Median, and Mean of Aerosol Size
Geometric Mean:
Fall 2008
By Wen-Whai Li
Particle Size Distributions

12. Particle Size Distributions
Moment Averages
Fall 2008
By Wen-Whai Li
Particle Size Distributions

13. Lognormal Distribution
Fall 2008
By Wen-Whai Li
Particle Size Distributions

14. Lognormal Distribution
Fall 2008
By Wen-Whai Li
Particle Size Distributions