HW4-6130 - Homework IV Coagulation, Nucleation &...

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Homework IV – Coagulation, Nucleation & Condensation (due March 30, 2010) 1. In an experiment using cadmium oxide smoke, the particle concentration was recorded as follows: Time from Start (min) Number conc. (#/cm 3 X 10 -6 ) 8 0.92 24 0.47 43 0.33 62 0.24 84 0.21 It is argued that the major mechanism in this system was Brownian coagulation only. Determine the coagulation constant from these data and compare with theory for monodisperse aerosols. (10%) 2. A log-normal aerosol model (BIMODALM.EXE) has been developed to help you understand the dynamic behavior of aerosols undergoing coagulation and/or condensation. Instruction of how to run the program is provided in “README.TXT” and “INPUT HELP.DOC”. Use it to study the following scenarios: (a) coagulation only – run for a total time of 10 s (which is equal to the product of time step (dt) and total number of steps (IT)); (b) condensation only – run for a total time of 1×10 -2 s. Use the default values specified in INPUT and choose the uni-modal option. However, for each scenario, choose two σ g ’s (1 and 2). Plot the number concentration (N), particle diameter (d g ), geometric standard deviation ( σ g ) and saturation ratio (S) as a function of time for each scenario. In addition, plot particle size distributions at the beginning and at the end of each scenario. Report your observation and explain why it is so. (20%) 3. It is desired to quench the coagulation of an aerosol in the free molecular regime ( d p << λ ). Determine the dilution ratio if the coagulation rate is to be reduced to 1% of its original value by isothermal, constant pressure dilution with particle-free gas. If the rate is to be reduced by the same factor by a reversible adiabatic expansion, determine the volume expansion ratio
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This note was uploaded on 09/11/2011 for the course ENV 6130 taught by Professor Wu during the Spring '08 term at University of Florida.

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HW4-6130 - Homework IV Coagulation, Nucleation &...

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