# 6: Modeling Case Studies

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• 6.1: Surge Tank Model
Surge tanks act as standpipe or storage reservoirs that store and supply excess fluid to regulate levels in systems. In a system that has experienced a surge of fluid, surge tanks can modify fluctuations in flow rate, composition, temperature, or pressure. Typically, these tanks are located downstream from closed aqueducts or feeders for water wheels. A surge tank can act as a level and pressure control within the entire system.
• 6.2: Heated Surge Tank
A surge tank is an additional safety or storage tank that provides additional product or material storage in case it becomes needed. Heat exchange can be added to surge tanks, which provides temperature control for the tank. Within a system these tanks can appear as distillation columns, reboilers, heated CSTR’s, and heated storage. They can increase production rates by allowing a batch of product to finish reacting while the initial tank is reloaded.
• 6.3: Bacterial Chemostat
Bioreactors are used to grow, harvest, and maintain desired cells in a controlled manner. These cells grow and replicate in the presence of a suitable environment with media supplying the essential nutrients for growth. Process control systems must be used to optimize the product output while sustaining the delicate conditions required for life. These include, but are not limited to, temperature, oxygen levels (for aerobic processes), pH, substrate flowrate, and pressure.
• 6.4: ODE and Excel CSTR model with heat exchange
A CSTR (Continuous Stirred-Tank Reactor) is a chemical reaction vessel in which an impeller continuously stirs the contents ensuring proper mixing of the reagents to achieve a specific output. Useful in most all chemical processes, it is a cornerstone to the Chemical Engineering toolkit. Proper knowledge of how to manipulate the equations for control of the CSTR are tantamount to the successful operation and production of desired products.
• 6.5: ODE and Excel model of a Simple Distillation Column
In simple distillation, two liquids with differing boiling points are separated by immediately passing the vapors from the reboiler to a condensing column which condenses the vapor components. As a result the distillate is not usually pure but its composition may be determined by Raoult’s Law. Consequently, simple distillation is usually used to separate binary mixtures where the boiling temperatures of the individual components are usually significantly different.
• 6.6: ODE and Excel model of a Heat Exchanger
In process industries, heat exchangers are designed to transfer heat from one fluid to another. Heat exchangers have many different applications, especially in chemical processes, air conditioning, and refrigeration. They are classified by their design and type of flow.
• 6.7: ODE and Excel Model of an Adiabatic PFR
A plug flow reactor (PFR) is a tubular reactor used in chemical reactions. Reactants enter one end of the PFR, while products exit from the other end of the tube. A PFR is useful because of high volumetric conversion and good heat transfer. PFRs carry out power law reactions faster than CSTRs and generally require less volume.
• 6.8: Modeling and PID Controller Example - Cruise Control for an Electric Vehicle
Controls principles developed in this course can be applied to non-chemical engineering systems such as automobiles. Some companies, such as NAVTEQ, are developing adaptive cruise control products that use information about the upcoming terrain to shift gears in a more intelligent manner which improves speed regulation and fuel economy. This case study will examine the basics of develop a speed controller for an electric vehicle.
• 6.9: Blood Glucose Control in Diabetic Patients

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