Aerosol Physics and Particle Control

1. Aerosol Physics and Particle Control

2. PM Particle Shape: -can be found in spherical, rectangular, fiber, or many other irregular shape -shape is important. Affects: -particle behavior -transportation -control technology -effect on the respirotary system (fiber shaped particles particularly harmful to the lungs when they are inhaled, since it is more difficult to remove once they are settled or have clung to air ways.

3. PM • Muallimköy ortam havasından toplanan partiküllere ait SEM fotorafı

4. Particle Size • The most important parameters since it affects: • Behavior • Transport • Health effects • Control technology selection Very large range from 0.01 mm to 100 mm A dust fall following a volcano contains large particles in the range of millimeters that can settle down in a few hours and smal particles (um range) can stay airborne for months.

5. Human Respiratory System • 3 major regions: • Head airways region • Tracheobronchial region (thoracic) • Pulmonary or alveolar region O2 –CO2 transfer take place in the pulmonary region. For an adult total area of this gas exchange region is 75 m2 and total length of the pulmonary vessels is about 2,000 km. An adult person breathes about 10-20 times per minute and inhales about 10-20 liters of air/min.

6. Particle Size Categories • Based on behavior in the human respiratory system 3 categories can be defined: • Inhalable particles • Thoracic particles • Respirable particles

7. Particle Size Categories

8. Inhaled Particle Deposition in Human Respiratory System • Deposition of Inhaled Particles in the Human Respiratory Tract and Consequences for Regional Targeting in Respiratory Drug Delivery, Joachim Heyder total Head airways Upper bronchial Lower bronchial Alveolar

9. Size Distribution • Particle Diameter The highly irregular shape together with the different densities depending on the composition of the particle complicates its size definition. A particle’s size refers to its diameter There are various definitions for the diameter.

10. Size Distribution • Particle Diameter • Equivalent volume diameter • Stokes diameter • Aerodynamic diameter

11. Particle Diameter • Equivalent volume diameter (de): diameter of a sphere that would have the same volume and density as the particle Assume that following irregular shape has a volume of V, de will be the diameter of sphere whose volume equals to V. 20 mm

12. Particle Diameter 2. Stokes diameter (ds): diameter of the sphere that would have the same density and settling velocity as the particle.

13. Particle Diameter 3. Aerodynamic diameter (da): diameter of the sphere with a standard density (1.000 kg/m3) that would have the same settling velocity as the particle

14. Particle Diameter de only standardizes the shape of the particle by its equivalent spherical volume ds standardizes the settling velocity of the particle but not the density da standardizes both the settling velocity and the particle density. Thus da is a convenient variable to use to analyze particle behavior and design of particle control equipment

15. Particle Size Distribution

16. How to display particle size distribution? 0.02 0.20

17. When shown as written in the table, we see that number of particles with diameter between 0.01 - 0.03 um equals to particles with diameter between 0.1 and 0.3 um however, diameter range in the first one is only 0.02 um while in the second is 0.2 um (1000 times bigger than the first range) 0.02 0.20

18. ni = the value of thenumber size distribution function (#/μm/cm3) The area of each rectangular gives the number of particles between Dp2 and Dp1 (Ni) Ni = niΔDp ΔDp = Dp2-Dp1 (μm)

20. n(Dp) (/um/cm3) Dp, um • Infinitely smallΔDp  dDp Let n(Dp) denote the continous function of size distribution n(Dp) dDp =Particle concentration with the diameters between Dp and Dp + dDp (#/cm3) dDp Typical display of distribution function n(Dp)

21. Normalized Size Distributions • Normalized size distribution ( ) can be obtained by: The fraction of particles with diameters between Dp and Dp + dDp to the total number of particles in one cm3 air Unit of normalized number distribution: μm-1

22. Surface Area,Volume and Mass Distributions • Surface area distribution ns(Dp) • Mass distribution m(Dp) Y:Characteristic function

23. Characteristic Functions for Particle Size Distributions (Y(Dp))* *assuming particles are spherical

24. Logaritmic Size Distributions • Since particles’ sizes vary over a very large range, use of logaritmic scale for Dp is more appropriate.

25. Log Scale Size Distributions Number of particles with diameters between logDp and logDp + dlogDp

26. Number Surface Volume Seinfeld ve Pandis

27. Parameters of particle size distributions • Mean:Averaged diameter of the sampled particle stream (number distribution) N= Total number of particles (mass distribution) mT = Total mass of particles

28. 2. Median: taneciklerin %50’sinin büyük, %50’sinin küçük olduğu çap değeri • Mode: • The most frequent diameter

29. Beside mean values, it is important to know the how distribution differs from these mean values. For all three distribution shown above, the mean diameters are the same while distribution width is different.

30. Variance Standard deviation:a measure of the distrubition width StandardDeviation=

31. Normal (Gaussian) Distribution The mean of the population Normal Distribution Function

32. Normal (Gaussian) Distribution Standard deviation (s) gives the characteristic width of the symetric number size distribution. 68.2% of the particles are between dp,mean –s and dp,mean + s, 84.1% of it with diameters smaller than dpmean+s , and 15.9% of it with diameters smaller than dpmean-s.

33. Are the particles in various air streams show a normal distribution?

34. Log-Normal Dağılım They mostly show a lognormal distribution Dp,g=0.4μm σg=2.5 Asıltı parçacıkların %68.2’si Dpg/σgile Dpgσgarasındadır. For lognormal distributions, Dpg =Dp,median

35. Geometrik Ortalama ve Geometrik Standart Sapma

36. Tanecik Boyut Dağılımının Log-Olasılık Kağıtta Gösterimi taneciklerin %50’sinin küçük olduğu çap (Dp,50) Çap, um Belirtilen Boyuttan Daha Küçük Olma Yüzdesi

37. Tanecik Boyut Dağılımının Log-Olasılık Kağıtta Gösterimi Eğer dağılımdan hesaplanan noktalar bir doğru oluşturuyorsa dağılımın log-normal olduğu söylenebilir. Tane sayısı, alanı,hacmi veya kütlesi için oluşturulabilir ve her dağılım için %50’sinin küçük olduğu çap bulunabilir. Örnek: Dpg = 0.5 mm ise, bu taneciklerin %50sinin bu çaptan küçük olması demektir. 100 tanecik varsa toplam , 50’sinin çapı 0.5 mm’nin altındadır. Çap, um Belirtilen Boyuttan Daha Küçük Olma Yüzdesi

38. Örnek • Tane sayısı (n(Dp) ve yüzey alan boyutdağılımını çizin (ns(Dp). Dağılımları karşılaştırın. • Bu örneklenmiş asılı taneciklerin log-normal bir dağılım gösterdiği söylenebilir mi?

41. b) Bu dağılım log-normal mi?

42. σg=Dp,84.1/Dp,50 = 2.0 0.16 Dpg=0.08

43. Moudi Impactor for Mass Size Distribution

44. Optical Particle Counter

45. Differential Mobility Analyzer

46. Aerodynamic Aerosol Sizer (APS)

47. Motion of Particles in a Fluid In all particle control technologies, particles are separated from the surrounding fluid by the application of one ore more forces: -gravitational -inertial -centrifugal -electrostatic Those forces cause the accelarate the particles away from the direction of the mean fluid flow, toward the direction of the net force The particles must then be collected and removed from the system to prevent ultimate re-entrainment into the fluid Therefore we need to know the dynamics of particles in fluids

48. Motion of Particles in a Fluid

49. Drag Force • FD = CDAppFv2r • FD=Drag force, N • CD=Drag coefficient • Ap=Projected area of particle, m2 • pF=Density of fluid, kg/m3 • vr= relative velocity, m/s Drag coefficient must be determined experimentally since CD = f(particle shape and the flow regime characterized by Reynolds number)

50. Stokes’ Law