Advanced Air Pollution Control and Engineering

Electrical Properties

Covers aerosol charging theory, unipolar aerosol chargers, bipolar aerosol chargers, and the equilibrium charge distribution. Introduces aerosol instrumentation based on electrical properties, including aerosol electrometer, electrostatic precipitators, transmission electron microscopy samplers, and aerosol electrical mobility analyzers.

Slides and Lecture Notes

Slide Deck: link

Reading

Reading: Hinds Chapter 15.

Homework

⌨ Assignment

  1. A Differential Mobility Analyzer (DMA) column is operated at a sheath flow rate of 10  L  min−110\;L\; min^{-1} and a sample flow rate of 1  L  min−11\;L\;min^{-1}. The flows are balanced. The radial dimensions r1r_1 and r2r_2 and length ll of the DMA column are given by:

ParameterValue
r1r_10.937×10−2  m0.937\times 10^{-2}\;m
r2r_21.961×10−2  m1.961\times 10^{-2}\;m
ll0.44369  m0.44369\;m

  1. If a voltage of −1400  V-1400\; V is applied to the inner column, what is the nominal diameter of singly, doubly, and triply charged particles transmitted through the column. Estimate the relative fraction of singly, doubly, and triply charged particles transmitted. You can assume that the true number concentration is constant across all sizes. You can also assume charge equilibrium.

  2. A 100 nm particle with single charge is transmitted through the DMA. Assuming that you add a second charge to the particle, calculate what would its apparent diameter be when selected by a DMA.

  3. Plot the ideal Knutson and Whitby transfer function against mobility for this mode of instrument operation.

CC BY-NC 4.0 Markus Petters.