in Wiley InterScience (www.interscience.wiley.com).Axial thermal gradients play a key role in monolithic diesel particulate filters. For complete particulate regeneration, the ignition location must be near the leading edge of the diesel particulate filter. A new reduced model in terms of the capacitanceweighted and mixing cup average temperature is formulated here using the Liapunov-Schmidt reduction technique to describe the ignition behavior and account for the axial variation. The major advantage of the reduced model is that one can neglect the details of the fine scale dynamics and focus on the large scale dynamics. This new, reduced model has the ability to accurately predict two important ignition characteristics: ignition time and ignition length. Based on the reduced model results, it is shown that the thermal dispersion [a coupling of transverse diffusion (short-scale) and axial convection (long-scale)] plays a dominant role on ignition.
This paper demonstrates four web-based instructional tools for heat and mass transfer based on JAVA applets. These tools are closely related to topics in two chemical engineering courses: transport phenomena and chemical reactor design. They simulate four classic problems which are one dimensional unsteady mass diffusion, one dimensional unsteady-state heat conduction in slabs, cylinders and spheres, Heisler charts for unsteady state heat transfer, and reaction and diffusion in porous catalytic substrates. They provide students with a dynamic observation of heat and mass transfer process unavailable in traditional textbooks. Educators and instructors can use these tools to enhance students understanding of the concepts of heat and mass transfer. mass transfer processes. These applets are a part of "Web Instructional Tools for Engineering," a one year project funded by the Michigan Space Grant Consortium. These four JAVA applets were to be developed with two goals in mind: to be visual enough to enable students to capture transport concepts, and to be interactive to keep the students' interest. Description of JAVA applets 1. One dimensional unsteady mass diffusion coefficients, thermal conductivities and heat capacities. The student can learn how these parameters affect the heat conduction through the comparison of the different simulation results. For example, the student can verify when internal resistance is negligible (Bi=hL/k < 0.1) with this applet.
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