Creating a dynamic model of a system involves multiple steps.

1. Identify objective for simulation
   • what do we want to accomplish
   • define which inputs should be related to which outputs
2. Draw a schematic diagram, labeling process variables
   • label relevant process variables
3. List all assumptions
   • used also to simplify model
4. Determine spatial dependence
   • Yes: Partial Differential Equation (PDE)
   • No: Ordinary Differential Equation (ODE)
5. Write dynamic balances for conserved quantities
   • energy
   • mass
   • momentum (Impuls)
   • electric charge
   • species (chemistry)
6. Add other relations
   • geometry
   • thermodynamics
   • reactions
   • …
7. Degrees of freedom: number of equations = number of unknown variables?
8. Classify inputs as
   • Fixed constants
   • Disturbances (cannot be controlled, might or might not be measurable)
   • Manipulated variables (manually or by solver/controller)
9. Classify predicted variables (e.g. outputs)
   • States
   • Controlled variables (set point, optimization objective)
10. Simplify balance equations based on assumptions
11. Simulate steady state conditions (if possible)
12. Simulate the output with an input step: dynamic response