HYSYS Operations Guide

Operations Overview 1-5
and streams, you can model a wide variety of oil, gas,
petrochemical, and chemical processes.
Included in the available operations are those which are
governed by thermodynamics and mass/energy balances, such
as Heat Exchangers, Separators, and Compressors, and the
logical operations like the Adjust, Set, and Recycle. A number of
operations are also included specifically for dynamic modeling,
such as the Controller, Transfer Function Block, and Selector.
The Spreadsheet is a powerful tool, which provides a link to
nearly any flowsheet variable, allowing you to model “special”
effects not otherwise available in HYSYS.
In modeling operations, HYSYS uses a Degrees of Freedom
approach, which increases the flexibility with which solutions are
obtained. For most operations, you are not constrained to
provide information in a specific order, or even to provide a
specific set of information. As you provide information to the
operation, HYSYS calculates any unknowns that can be
determined based on what you have entered.
For instance, consider the Pump operation. If you provide a
fully-defined inlet stream to the pump, HYSYS immediately
passes the composition and flow to the outlet. If you then
provide a percent efficiency and pressure rise, the outlet and
energy streams is fully defined. If, on the other hand, the
flowrate of the inlet stream is undefined, HYSYS cannot
calculate any outlet conditions until you provide three
parameters, such as the efficiency, pressure rise, and work. In
the case of the Pump operation, there are three degrees of
freedom, thus, three parameters are required to fully define the
outlet stream.
All information concerning a unit operation can be found on the
tabs and pages of its property view. Each tab in the property
view contains pages which pertain to the unit operation, such as
its stream connections, physical parameters (for example,
pressure drop and energy input), or dynamic parameters such
as vessel rating and valve information.
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