HW2-6130-Solution

# HW2-6130-Solution - Homework II Single Particle Motion...

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Homework II – Single Particle Motion, Diffusion, Thermal Forces (due 02/19/2008) 1. What is the settling velocity of an asbestos fiber in the shape of a cylinder 1 m in diameter and 10 m long at standard conditions? Assume random orientation and a density of 2.5 g/cm 3 . Neglect slip correction. (10%)

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2. (a) Derive an expression for the collection efficiency (as a function of particle size) for a multi-layer settling chamber (see the figure below) with N equispaced sections. Assume a uniform flow, uniform distribution of aerosols at the inlet, and negligible slip correction. Neglect diffusion. (10%)
3. A typical mass size distribution from a diesel-equipped coal mine is bimodal, with one mode for the diesel smoke particles at 0.16 m, and the other for coal dust at 7 m. The saddle point between the modes is at an aerodynamic diameter of 0.8 m. If you are asked to use a single-stage impactor to separate diesel smoke from coal dust in a sample of air from a coal mine, what nozzle diameter will you choose if the total sample flow rate is 2.5 l/min and 8 nozzles are used? (10%)

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4. Review "A Simple Derivation of the Cutpoint of an Impactor", J. Aerosol Sci. , 10 , 1317-1320, 1999. Compare the theory with that discussed in the textbook. (10%) Textbook Article Stokes Number 0.24 and 0.59 for circular and rectangular jet,
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HW2-6130-Solution - Homework II Single Particle Motion...

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