Chemical Engineering October 2016 - 76

FIGURE 3. Valuable information about an object
can be found quickly in the Object Browser
FIGURE 2. The Object Browser in Microsoft Excel
contains all the properties and methods associated
with a particular object
be sources of data-transfer errors.
VBA programs that automate data
transfer eliminate that human error.
One of the greatest benefits of
HMB extraction by VBA is that the
VBA communication avoids the
potential for human errors in data
transfer that are common in copyand-paste
techniques. This article
presents code examples and basic
programming techniques to aid
chemical engineers who are familiar
with the basics of Hysys or other
process simulators.
Getting started with Excel VBA
VBA is based on object-oriented programming
techniques, a hierarchism
of objects, properties and methods.
An object is an item of the simulation,
such as a Material Stream or
Heat Exchanger Operation. Each
object has its own properties, such
as Temperature for Material Streams
and Duty for Heat Exchanger Operations.
Each object and its properties
also have their own methods, such
as GetValue, which returns the value
of temperature or heat duty in the
user's specified units.
Let us say the simulation has a
material stream (an object) named
" 100 " , which has several properties,
such as pressure, mass flowrate,
component mass fractions and so
on. The engineer may want to extract
these properties and populate
them in the spreadsheet. Example
code utilizing the GetValue command
is shown in the box on p. 68.
FIGURE 4. Ensuring that the proper references are
added to the Excel file is crucial for VBA code to
execute correctly
Tips and tricks
The transfer of stream data from
process simulators to Excel via VBA
is fast and convenient. However,
engineering review of the material
balance results is required to catch
simulation errors. The engineer
should consider that a process simulator
like Hysys is not able to calculate
stream properties for all conditions.
For example, properties that
may not be calculated are viscosity
in two-phase streams or a property
outside of the fluid package's
temperature limits. That stream
property would read as "  "
and VBA would not extract the
data correctly.
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Chemical Engineering October 2016

Table of Contents for the Digital Edition of Chemical Engineering October 2016
