Chapter 3

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# Chapter 3 - PowerPoint PPT Presentation

Chapter 3. Dynamic Modeling (Part 2). Unsteady-State Mass Balance. Unsteady-State Energy Balance. Constitutive Relationships. Usually in the form of algebraic equations. Used with the balance equations to model chemical engineering processes. Examples include: Reaction kinetic expressions

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Presentation Transcript

### Chapter 3

Dynamic Modeling

(Part 2)

Constitutive Relationships
• Usually in the form of algebraic equations.
• Used with the balance equations to model chemical engineering processes.
• Examples include:
• Reaction kinetic expressions
• Equations of state
• Heat transfer correlation functions
• Vapor/liquid equilibrium relationships
Different Types of Modeling Terms
• Dependent variables are calculated from the solution of the model equations.
• Independent variables require specification by the user or by an optimization algorithm and represent extra degrees of freedom.
• Parameters, such as densities or rate constants, are constants used in the model equations.
Dynamic Model for CST Thermal Mixer
• The model assumes perfect level control:
Dynamic Model for CST Composition Mixer
• The model assumes perfect level control:
Dynamic Model for Tank Level
• Accumulation of mass in the tank is equal to the mass flow rate in minus the mass flow rate out.
• For a gravity drained tank,
Dynamic Model for Tank Level
• Actuator on flow out of the tank.
• Process model
• Level sensor since the level sensor is much faster than the process and the actuator
Dynamic Model for CSTR
• Actuator
• Process

model

• Sensor