Chapter 3
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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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Chapter 3

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Chapter 3

Chapter 3

Dynamic Modeling

(Part 2)


Chapter 3 4007595

Unsteady-State Mass Balance

Unsteady-State Energy Balance


Constitutive relationships

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

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

Dynamic Model for CST Thermal Mixer

  • The model assumes perfect level control:


Chapter 3 4007595

Dynamic Model for CST Composition Mixer

  • The model assumes perfect level control:


Dynamic model for tank level

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 level1

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


Chapter 3 4007595

Model for CSTR with a First Order Reaction


Chapter 3 4007595

Dynamic Model for CSTR

  • Actuator

  • Process

    model

  • Sensor


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