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Dynamic Simulation Structure and Configuration

Dynamic Model Setup

A dynamic model in DWSIM can be configured by starting from a solved flowsheet in steady-state mode. Additionally, each Boundary Material Stream must have a Pressure or Flow specification. In dynamic mode, a Valve Unit Operation connected to these streams will determine the Pressure-Flow relationships for the rest of the flowsheet as the remaining Unit Operation blocks get solved at each time step (Figure 53).

<span id="fig:dyn1" data-label="fig:dyn1"></span>Example of a valid flowsheet for dynamic mode. Both boundary streams are connected to valves. The inlet stream has a Flow specification while the outlet stream is Pressure-specified.

Example of a valid flowsheet for dynamic mode. Both boundary streams are connected to valves. The inlet stream has a Flow specification while the outlet stream is Pressure-specified.

Event Sets

Dynamic Events are property changes that occur in a defined time step. A group of Dynamic Events is called an Event Set.

Property change events can transition from a previous state ’suddenly’ (step change), linearly, log-linearly, inverse log-linearly or randomly between the two states (reference state and the one defined by the event itself).

Cause-and-Effect Matrices

Cause-and-Effect Matrices consist in a set of property changes that occur after an alarm is activated during the dynamic simulation. Each alarm activation triggers a property change defined by the user.

Integrators

Integrators are the components responsible to run the flowsheet sequentially in a dynamic simulation. They can be configured to run during a specified duration in fixed intervals, triggering the mass and balance solvers according to the user preference.

Monitored Variables

Each Integrator can have a set of monitored variables, that is, a set of object properties which will have their values stored after each integration step. Monitored variables can have their values exported for later visualization in the Spreadsheet.

Schedules

The Schedule is a set of definitions which, together, can be considered as a case study in the context of a dynamic simulation. A Schedule must have the following items defined in order to run:

  • Associated Integrator (Required)

  • Event Set (Optional)

  • Cause-and-Effect Matrix (Optional)

  • Initial Flowsheet State (Optional)

A Schedule can be run from the Integrator Controls window. After running a Schedule, the results (values of monitored variables at each step) can be copied to a new spreadsheet.