In order to understand the concept of stream-based specifications, it is necessary to understand what is meant by the following terms:

• Specifications are objects with which you input parameters into CADSIM Plus unit modules so that the module can perform the calculations that you require
• Unit modules are individual pieces of equipment or controls that populate your simulation model. These unit modules usually have real-world counterparts, such as tanks, heaters, separators, and pumps
• Streams are pipes that connect unit modules
• Stream-based specifications allow unit modules to ask the streams to provide specification values

Some simulators use unit-based dialog boxes which only allow you to pick from a list of descriptions and numerical entry fields. While this method is simple, it drastically restricts the type of stream information that can be asked for by the units. It also restricts each unit to a finite number of named streams, because the dialog boxes are already built to give a predefined list to you. With CADSIM Plus, stream-based specifications allow you unlimited choices in variables which you can specify. Having stream-based specifications in CADSIM Plus allows you to add any number of outlet streams to units such as Separators, and still have flexible specification options.

Although CADSIM Plus allows simple numeric specifications, these are just one of a variety of options that are available to you. Our FlexSpec™ technology allows you nearly unlimited flexibility in specifying your process problem the way that you want to. Just one example of specification flexibility is:

• An outlet temperature could be set to a value, or to 5 degrees above an inlet temperature, or to be the same as the stream's boiling point (with rise), or to 20 degrees of superheat.

All specification objects give you the ability to use equations to specify your model. You can equate one value to another, ratio or calculate values for any unit module or stream parameter. If you need even more complexity, you can use a series of equations or cascading equations. Values can be filtered, transformed, or passed through PID or Fuzzy Logic controllers. Different values can even be selected for differing process conditions.

CADSIM Plus specifications appear graphically on your flowsheet model so that you can survey and adjust these relationships quickly and easily. There are no mystery values hidden away.

The specification flexibility of CADSIM Plus is often the feature that users mention first when they compare our simulator to others that they have used in the past. If you want to specify your process model in ways that make sense to you, and yield results that are easily compared with your process, then CADSIM Plus is your best choice.