(547f) A Micro-Macro Transport Sequence for the Che Curriculum: Role of Scaling

The transport sequence, i.e. momentum, mass and energy, in many departments of chemical engineering is taught following a unit operation-based approach (MacCabe et al., 2004 )or, alternatively, by using concepts already scaled-up (Felder and Rousseau, 2004) from microscopic variables giving the impression to students that every case is ?divorced? from a general type of conservation equation. Thus, students perform analysis by using macro-balances for every process they face without a proper up-scaling (Arce et. al., 2005; Oyanader et al., 2007) from the microscopic concepts so important to achieve a masterful command of the concepts and to understand limitations of process descriptions. Moreover, the introduction course on mass and energy balances follows the same type of approach without, for example, selecting proper control volumes or surfaces in connection with the fundamentals conservation equations (Higgins et al., 2007). One of the results is that when students need to apply these concepts to the micro (and even nano) scales, they often get confuse since it looks like that an entirely new discipline must be learned.

In the approach we are experimenting with at Tech, students follow a different sequence. This is rooted on fundamentals conservation principles (based on microscopic variables) for the energy, momentum, and then mass processes. Students are introduced to heat transfer by radiation (no ?media?) first; then they are exposed to conduction and diffusion (media without a bulk motion); afterwards, they learn momentum conservation in order to describe convective-based transport and, finally they are exposed to diffusive-convective transport. All the concepts are taught in an integrated sequence that allow students to sequentially learned concepts and build knowledge. In addition, concepts are introduced at a microcospic level and, by spatial scaling to various levels, i.e. averaging in lines, surfaces, or volumes, students are automatically introduced to the key up-scaling concepts; these are needed to describe any process ranging from micro-level to a macro-level. The first introductory course is now centered on process analysis from a fundamental point of view and with the identification of the proper averaging surfaces or volumes.

In this presentation, details about the sequence and illustrative examples will be offered. In addition, future adjustment will be also discussed. The role of multi-scale systems (including molecular-level descriptions) now of paramount importance in chemical engineering system will be integrated in the discussion.

References:

1. McCabe, W.; J. Smith and P. Harriot, ?Unit Operations of Chemical Engineering?, McGraw Hill Chemical Engineering Series, 2004, N. Y., New York. 2. Felder, R. and R. Rosusseau, ?Elementary Principal of Chemical Processes?, J. Wiley & Son, (2004), N.Y., New York. 3. Arce, P.; M. Quintard and S. Whitaker, 2005, ?The Art and Science of Up-scaling,? Chapter 1 in Chemical Engineering: Trends and Developments, edited by M.A. Galán and Eva Marin de Valle, John Wiley & Sons, Ltd., England, (2005). 4. Oyanader, M.; P. Arce and S. Whitaker, ?The Catalytic Pellet: A Rich Learning Environment for Up-Scaling?, Chemical Engineering Education, (2007, under review). 5. Higgins, B.; R. Cerro and S. Whitaker, ?Material Balances for Chemical Engineers?; web site http://www.higgins.ucdavis.edu/