An Introduction to HYSYS

     The purpose of this and the following pages is to introduce you to the primary tool that you will be using in the design classes, HYSYS. Now HYSYS comes with a number of excellent reference and tutorial manuals. The Design Lab should be equipped with two complete sets of the manuals. Each set contains the following books: Getting Started, Quick Reference, Tutorials, Applications, Reference Volume 1, and Reference Volume 2. PLEASE do not remove these from the room. The same six volumes may be accessed electronically in Adobe Acrobat format either from the start menu as shown below or via the World Wide Web.

Getting Started and Tutorials are available at The Applications book is available at It is far easier to look at the actual books than to worry through the Acrobat Reader, so, again, please don't take them from the room. Note that all referals to manuals are in yellow and if the manual in question is on the HYSYS web page, like the Tutorials Book, then the reference will also be a link.

     Because I don't believe in duplication of effort (especially my own), this web page is intended to be complimentary to those manuals. Here on the web page, I hope to fill in the blanks left by the books, serve as a quick reference for some items, and give pointers and links as to the places in the manuals to look immediately for the answers to your questions. Most importantly, however, these pages will provide you with the tips you will need to get your specific tasks done on the specific computer system you will be working with and with this specific version of HYSYS. These tips will include information for both CENG403, where you learn to design individual units, and CENG404, where you will design an entire plant (in fact, this is the only place that you will find many tips for 404, so don't forget to come back and read them again when you start needing them). HYSYS is not the best program for group work (Aspen isn't any better believe me), therefore an entire section has been devoted towards teaching you the best way to work in groups. By the way, NT will allow two different users to edit the same file at the same time. This is bad. If you do this, only one person's work will get saved.


A Little About HYSYS


     The goal of programs like HYSYS and Aspen is, of course, to provide you with the capability to design an entire process as completely and accurately as possible. Most (though not all) of the differences between the two lie in their user interfaces. Having gone through the design class with Aspen, I am of the personal opinion that HYSYS has a much better and intuitive interface than Aspen. You have the option of using either simulation package, but I recommend using HYSYS unless you run against something that only Aspen will do. I will try to warn you of all the limitations of HYSYS that you might encounter in advance.

     Unlike Aspen, HYSYS does not wait until you've entered everything before beginning calculations. It always calculates as much as it can at all times and results are always available, even during calculations. Any changes that you make to the data are automatically propagated throughout the program to anywhere that entry appears and all necessary recalculations are instantly carried out. It tends to be a lot easier to catch errors this way as you build your simulation. However, there are times when you will not want HYSYS calculating the entire flowsheet over again every time you make a small change. Hence, the existence of the environments. While you are in one environment, calculations in the other environments are placed on hold. Every case (as HYSYS calls each individual simulation file) has two or more environments. The one that contains all the items you expect to see, the streams, unit operations such as reactors, separators, columns, mixers, etc., and various utilities, is the simulation environment. At the top of that environmental hierarchy (and the only one required) is the Case environment and the Main flowsheet. (Aside: both the name "Case" and the tag "Main" are defaults and can be changed in the "Main Properties" view under the Simulation menu). Though the entire simulation may be placed in the Main flowsheet, columns and templates are automatically brought in as Sub-flowsheets. Sub-flowsheets can be thought of as modular programs. You can have as many as you like, nested as deep as you like (though you tend to not need to put additional sub-flowsheets under a column flowsheet).

     The other environment, and the one you actually have to deal with first when you start a case, is the basis environment. The basis environment is the place that you define the thermodynamic package you wish to use (Peng-Robinson, Margules, etc.), the components that will be used in your simulation and any reactions that may occur. If dealing with a Petrochemical application, there is also an oil environment that may be reached only from the basis environment.

     There are two files that HYSYS reads whenever you start HYSYS. One of these is the Preferences File, the other is the workbook format file. The preferences file tells HYSYS many important things like which units you want to use, where to look first for your stored files etc. You can have multiple preference files saved (or you can just build up various unit sets, etc., in one file you alter upon need), but the one that is loaded upon startup is the file named hysys.prf in the directory from which HYSYS is started. If you launch HYSYS from your start menu, your user's profile has been configured with Y:\Hysys as the start directory (note that if you are not in a design class group, you won't have a Y drive, because the purpose of theY drive is to save group work). If you look at the contents of that directory you will see, in addition to some other stuff, that I have placed a hysys.prf file in there for you. That is the file that must be overwritten if you want to make changes to your default preferences (though changes are automatically saved to the preference file when you save your simulation, so overwriting should not often be necessary).
     You may have noticed the other file I put there, hysys.wrk. That file is responsible for the appearance of your workbook. The workbook shows you the contents of every stream in your process and the connections of every unit (if you really wanted to you could make your entire simulation using the Workbook and never even look at the PFD). Without the hysys.wrk file, unless the file has undergone changes to its workbook which got saved with that particular case, the default is for the workbook to only show two pages: Streams and Unit Ops. Now, if you've done any reading of the manuals or working of the tutorials you were propably expecting four pages: Material Sreams, Compositions, Energy Streams, and Unit Ops. The Workbook is much harder to work with without the extra info these pages provide. The file I provided restores these other pages, but again it is only automatically loaded if the Start Menu was used to launch HYSYS.
     Why am I telling you all this? Because there are a number of cases where you will not be able to use the start menu to do what you want. If you start a file by double clicking it (your simulations should all be stored under Y:\Hysys\Cases), without a hysys.prf file present, HYSYS will use the default file located on the NTserver called Hartsook. It is not configured for you and you cannot save changes to it. HYSYS will also fall back on that file if you do not have a Y drive. Moreover, any time you want to run one of HYSYS' or my example files, because of a failure of HYSYS to handle links or networks well, the only way you'll be able to see Hartsook (where all the sample files are located), is to double-click on one of your own files (causing HYSYS to "start in" a directory on Hartsook), then turn right around and close that file. Then, you may Open the example file. Note that HYSYS' examples are located in \\Hartsook\Hysys\SAMPLES, not in CASES as the manuals say, and that my examples are located in \\Hartsook\Hysys\SAMP403.
     What ever you are trying to do, if you used one of the above methods, HYSYS will not open with the correct Preference File. The first thing you should do once HYSYS opens is open Preferences under the Tools Menu. Then press Load Preference Set... . Load Y:\Hysys\Hysys.prf. At that point you may or may not need to import your workbook format. Push the Workbook button , on the toolbar to find out. If you do need to, then choose Import under the Workbook Menu and import the file hysys.wrk under Y:\Hysys.

Note: Should you somehow create a Hysys.prf file under your cases directory, DELETE or move it, as you will not be able to get to the example files on Hartsook with it there. An automatic way of telling if your preference file is based on the one I started you with or if it is HYSYS' default is the color of the background. HYSYS' preference file makes the background the same brown color as your desktop. My preference file uses a deep purple as the background color.

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