# hw11 - CE 561 Homework 11 Assigned due(1 Shetty et al(1992...

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CE 561 Homework 11: Assigned 11/16/09, due 11/30/09 (1) Shetty et al. (1992) studied gas-phase backmixing for the air-water system in bubble-column reactors by measuring RTDs of a pulse-injected helium tracer. The results of one particular experiment were as follows: Dimensionless Time 0.1 0.2 0.4 0.6 0.7 0.9 1.3 1.9 2.8 3.4 Normalized Concentration 0.00 0.01 0.56 0.97 1.00 0.88 0.48 0.17 0.02 0.00 Using the above data, (a) Determine the normalized variance of the RTD. (b) Find, N , the number of tanks in a tanks-in-series model that best matches the variance. (c) Find the Peclet number for a plug-flow-with-dispersion model that best matches this variance. (d) Plot the experimental RTD along with the tanks-in-series RTD using the N found in part (b) and the plug-flow-with-dispersion RTD using the Peclet number found in (c). Which gives the better fit? (e) For either model, can the fit be improved by fitting directly to the data rather than just matching the experimental variance? (2) A tracer study was conducted on a flow reactor, and it was found that the RTD was consistent with the tanks-in-series model, with N = 5. The mean total residence time in the system was 8 minutes.

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hw11 - CE 561 Homework 11 Assigned due(1 Shetty et al(1992...

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