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HW3-6130-Solution

# HW3-6130-Solution - Homework III(due 1 A filter bed of...

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Homework III (due 03/04/2010) 1. A filter bed of packing density 0.1 and fiber diameter 4 m for use in removing radioactive particles from a gas stream must provide an overall collection efficiency of at least 99.99% for particles of any size. Given a flow rate of air at 298 K, 1 atm of 1 m 3 /s, p = 1.2 g/cm 3 , and filter bed width and height of 1.5 and 1.0 m, respectively, determine (a) the necessary depth of the filter; (b) the most penetrating particle size (MPPS) and the corresponding single fiber efficiency; (c) the relative importance of single fiber efficiency due to interception, impaction and diffusion in collecting the MPPS; (d) filter quality at the MPPS. (16%)

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2. With increasingly stringent fuel economy standards, diesel engines appear to be attractive alternative power plants for passenger vehicles. However, despite its superior fuel economy, a diesel engine presents a challenging emission control problem. As the engine is operated in a manner to maintain low NOx emissions, particulate emissions exceed the exhaust standard. Thus, an additional scheme for controlling particulate emissions is necessary. One such scheme that has received extensive study is the filtration of exhaust particulate matter by a filter bed placed in the exhaust system. In this problem, we consider the design of a fibrous filter bed for this purpose. (Disposal of the collected particulate matter is a key problem, although we do not consider it here.) We will focus on the initial performance of the filter, that is, on the period during which the deposition of particles is not influenced by those already collected. The following conditions can be assumed for the exhaust filtration problem: = 0.05, T = 473 K, d f = 10 m, u = 8 cm/s, and p = 1 g/cm 3 . (a)

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HW3-6130-Solution - Homework III(due 1 A filter bed of...

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