The document discusses sub-flowsheet operations in HYSYS which allow breaking up large process simulations into individual process units. Each sub-flowsheet acts as a "black box" component that can be installed and viewed like other flowsheet objects. Sub-flowsheets contain their own fluid package, flowsheet objects, process flow diagram (PFD), workbook, and desktop for simulation of an individual process unit. This modular approach provides a flexible way to build complex simulations from separate sub-process components.

1. Sub-Flowsheet Operations 2-3
2-3
2.1 Introduction
The sub-flowsheet operation uses the multi-level flowsheet architecture
and provides a flexible, intuitive method for building the simulation.
Suppose you are simulating a large processing facility with a number of
individual process units and instead of installing all process streams and
unit operations into a single flowsheet, you can simulate each process
unit inside its own compact sub-flowsheet.
Once a sub-flowsheet operation is installed in a flowsheet, its property
view becomes available just like any other flowsheet object. Think of this
view as the “outside” view of the “black box” that represents the sub-flowsheet.
Some of the information contained on this view is the same
as that used to construct a Template type of Main flowsheet. Naturally
this is due to the fact that once a Template is installed into another
flowsheet, it becomes a sub-flowsheet in that simulation.
Whether the flowsheet is the Main flowsheet of a simulation case, or it is
contained in a sub-flowsheet operation, it possesses the following
components:
• Fluid Package. An independent fluid package, consisting of a
Property Package, Components, etc. It is not necessary that
every flowsheet in the simulation have its own separate fluid
package. More than one flowsheet can share the same fluid
package.
• Flowsheet Objects. The inter-connected topology of the
flowsheet. Unit operations, material and energy streams, utilities
etc.
• A Dedicated PFD. A HYSYS view presenting a graphical
representation of the flowsheet, showing the inter-connections
between flowsheet objects.
• A Dedicated Workbook. A HYSYS view of tabular information
describing the various types of flowsheet objects.
• A Dedicated Desktop. The PFD and Workbook are home views
for this Desktop, but also included are a menu bar and a tool bar
specific to either regular or Column Sub-flowsheets.