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Show > 3 Boundary Layer Destruction Model (Module 2) Given the bulk gas and wall temperatures as input, the second leg in the model calculates axisymmetric radial temperature and velocity profiles for each zone. The furnace is further partitioned into an appropriate number of concentric annular slices. Figure 7 shows typical profiles for a zone well downstream of injection. Typically the spacing between slices is smaller near the boundaries because of the steeper thermal and velocity gradients at the wall. To quantify the effect of wall quenching on thermal destruction, a time-temperature history is developed for each slice, and a simple chemical kinetic expression applied to each time-temperature path. Hence, the program calculates a set of concentration profiles, one for each slice. The sum of the concentration paths, weighted by the volume flow rate through the slice, crudely approximates a single destruction efficiency for well-mixed stack gasses. The velocity boundary layer is calculated based on fully developed flow. Both laminar and turbulent flow are considered. In each case, the bulk velocity (derived from the input mass flow and calculated density) is related to the maximum velocity by appropriate equations. Then the average slice bulk Temperature -.y^~. < 1 - 1 - 6 "^v^ 5 43 211 Gas temperature profile •Turbulent velocity profile bulk QJ \ Radial position Figure 7. Typical Radial Temperature and Velocity Profiles for a Zone Showing Slices 5.5.10 |