Almost all chemical engineering curricula feature a sequence of two (if on a semester system) or three (if on a quarter system) courses involving the term transport in the course name. These courses are typically offered in the junior (or third) year of the program and are termed Transport and Rate Processes at the University of Idaho. Transport Phenomena is a common name used in many other institutions. The three transport phenomena covered in these courses are momentum transport, energy transport, and mass transport [9].
These courses lay the theoretical foundation for understanding the processes occurring in chemical systems. All processes, whether they involve a simple fluid flow, transfer of heat, or a component, occur at the molecular level. The mechanisms of transfer of the quantities involved—momentum, energy, and mass—are analogous to each other. The theoretical analysis and quantitative results obtained from examining the molecular-level processes for momentum transfer can be extended and applied to the other two transport phenomena.
These courses typically begin with the mathematical description of phenomena associated with the flow of fluids. The similarity between fluid flow behavior and energy/mass transfer is used to extend the mathematical model of momentum transport to energy and mass transport. This quantitative analysis provides the key to understanding the factors that govern the rate of transfer of quantities of interest.
The topics covered in momentum transport include a fundamental description of viscosity and shear forces in a fluid, quantitation of turbulence and frictional losses, and energy balances in fluid systems. Processes occurring at the boundary of a fluid are examined from a microscopic or molecular viewpoint. Energy transport and mass transport build on these concepts to link the heat and mass transfer to the molecular processes in fluids. Figure 3.10 provides a broad overview of the transport phenomena topics and some important concepts.
Figure 3.10 Overview of transport phenomena.
The system behavior at the macroscopic level can always be linked to measurable parameters, such as temperature, flow rate, and so on, using a trial-and-error procedure. Empirical relationships obtained through such an exercise have a limited utility and validity for specific situations. Study of transport phenomena occurring at the microscopic level provides a theoretical basis for explaining the system behavior at the macroscopic level. Relationships between observed quantities and system parameters developed on the basis of this theoretical analysis are scientifically valid and have general applicability to other systems. Transport phenomena courses thus equip a student with the knowledge to analyze any situation based on sound science. This knowledge imparts an ability to predict accurately the system response to changes in operating parameters and hence an ability to increase the efficiency of operations, whether it is separations, heat transfer, or simply material flow. The quantitative tools acquired by the student are used in the design of heat transfer, fluid flow, and separations equipment.
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