Opening the Dynamic Simulation in Aspen Dynamics

Go to the location where you have saved the files and open the Examplel.dynfSle. The screen that opens contains several windows (see Fig. 7.7). 

The Process Flowsheet Window is where the control structure will be developed. The Simulation Messages window is where the progress of the simulation is shown and simulation time is displayed. The window in the upper left corner Exploring is where various types of controllers, control signals, and other elements can be found to drag and drop onto the flowsheet. 

The initial flowsheet has some default controllers already installed. In this simple, single-column process there is only one default controller, the pressure controller. It is 

There are four remaining manipulated variables (distillate flow rate, bottoms flow rate, reboiler duty, and feed flow rate) to control these four controlled variables. The issue of pairing which manipulated variable with which controlled variable is called control structure selection. A variety of different types of control structures will be discussed in this and subsequent chapters. 

We have not listed reflux in the hst above because the default configuration in Aspen Dynamics is to fix the mass flow rate of the reflux. We will discuss how this setup can be changed later in this chapter. 

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