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Air Pollution Tutorial: Calculating Settling Velocity & Efficiency, Assignments of Refrigeration and Air Conditioning

Solutions to tutorial problems from the university of western ontario's department of chemical and biochemical engineering air pollution course (cbe 4405 / cbe 9312). The problems involve calculating terminal settling velocities for spherical particles and the efficiency of gravity settlers and cyclones separators using stokes law.

What you will learn

  • What is the terminal settling velocity for a spherical particle with specific gravity 4 and a diameter of 1 µm?
  • What is the terminal settling velocity for a spherical particle with specific gravity 4 and a diameter of 0.005 µm?

Typology: Assignments

2020/2021

Uploaded on 06/12/2022

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The University of Western Ontario
Faculty of Engineering
Department of Chemical and Biochemical Engineering
Air Pollution (CBE 4405 / CBE 9312)
Tutorial # 04
Problem – 1
A spherical particle with specific gravity 4 is settling in air, calculate the terminal settling
velocity for those cases: (assume density of air is 1.2 kg/m3 and the viscosity of air is 1.8x10-5
m2/s)
i) Diameter of particles = 1 µm. (0.01µ -100 µ) “acceptable range for stokes law”
ii) Diameter of particles =0.005 µm. (Assume λ = 0.07)
Solution:
i)
V=9 . 811012(40001 . 2)
181. 8105=1. 21104m/sec
ii) D=0.005
μ
, very small.
pf3
pf4

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Download Air Pollution Tutorial: Calculating Settling Velocity & Efficiency and more Assignments Refrigeration and Air Conditioning in PDF only on Docsity!

The University of Western Ontario

Faculty of Engineering

Department of Chemical and Biochemical Engineering

Air Pollution (CBE 4405 / CBE 9312)

Tutorial # 04

Problem – 1

A spherical particle with specific gravity 4 is settling in air, calculate the terminal settling

velocity for those cases: (assume density of air is 1.2 kg/m

3

and the viscosity of air is 1.8x

m

2

/s)

i) Diameter of particles = 1 μm. (0.01μ -100 μ) “acceptable range for stokes law”

ii) Diameter of particles =0.005 μm. (Assume λ = 0.07)

Solution:

i)

V =

− 12

− 5

− 4

m /sec

ii) D=0.

μ , very small.

C

d

D

V

stoke

− 6

2

− 5

− 9

m /sec

V=C

d

*V

stoke

m/s

Problem – 2

Two particles A&B are released in air at the same time, what is the ratio of settling velocity of

particle A to that of particle B if the diameter of particle A is 10 μ, and for particle B is 1.00 μ, if

they have the same density.

Solution:

V

A

V

B

D

A

2

D

B

2

Problem - 4

Compute the efficiency (block and mixed) for a cyclone separator that has:

w i = 0.5 ft v c = 60 ft/s N = 5

D

o

= 2 ft D = 3 μm ρ p

= 125 lb/ft

3

μ = 1.21 x

Solution:

b

− 6

∗ 3. 28 ft / m )

2

− 5

m

= 1 − e

η b