Contents - Index

Function Info


The Function Information command will bring up a dialog window listing the built-in and user-defined internal functions, procedures and modules in library files.  



Eight buttons at the top of the dialog window determine the type of function information that will be presented.  Functions can be classified as internal or external.  Internal functions are built into the EES program and include the math and string functions and thermophysical properties.  Information for routines that are written in EES and saved as library files are accessed with the EES library routines button.  Dynamic link library programs written in Fortran, C, or other compiled languages are represented by the External routines button.  The remaining three buttons provide function information for application libraries, which currently include Heat Transfer, Mechanical Design and Component Library.  The last button provide access to User-defined application library.  Instructions on how to create this library are provided here.


Select the function or procedure from the list box on the left.  To select a function, click on the function name in the scrollable list.  The Function Info button will be enabled if descriptive or help information is available for the function you selected.  Click the button to view the information.  Depending on the format of the available information, the Function Info button may start the Windows Help program, Adobe Reader, or your browser.  


Clicking the Fluid Properties radio button sets the dialog to provide information on the built-in thermophysical properties.  An example of the dialog display is shown above.  The property data is divided into six groups which are associated with the 6 radio buttons that appear between the Function Info and Fluid Info buttons.


Real fluids represents the fluids for which liquid and vapor data are available, including supercritical and compressed liquid states.

Ideal gases are modeled assuming ideal gas behavior, so that enthalpy, viscosity and thermal conductivity depend only on temperature.

AirH2O is for low pressure (ideal gas) psychrometrics.  Additional psychrometric functions, such as Wetbulb, Dewpoint, Relhum, and HumRat are available for this fluid.

NASA provides access to the NASA Ideal Gas data base, which provides specific heat, enthalpy and entropy data for 1262 ideal gases.

Brines provides property information for brines (secondary refrigerants) as a function of temperature and mass concentration (%)

Incompressible provides property information for incompressible liquids and solids.  


Click one of the property group buttons.  The thermophysical property functions applicable for that group appear in the list on the left side of the dialog.  Specific information about the selected function can be viewed by clicking the Function Info button above the list.  The substances for which these functions can be applied are shown in the list on the right.  Click on the substance name in the scrollable list to select the substance.  A convention is used to help distinguish ideal gas and real fluid substances.  Substances represented by their chemical formula (e.g., CO2) are modeled as an ideal gas and use JANAF table reference values for enthalpy and entropy.  Substances with their name spelled out (e.g., CarbonDioxide) are modeled as real fluids and do not use JANAF table reference values.  Information on the range and origin of the property data correlation for the selected substance is available by clicking the Fluid Info button above the substance list.  


Thermophysical functions may require between 0 and 3 independent properties depending on the choice of function and substance.  If the function requires independent properties other than temperature, a box will appear with drop-down menus listing the alternatives available for the selected function-substance combination.  The example box will display a sample use of the function with the selected independent properties.  The small index edit box at the right of the example box provides a convenient way to customize the display in the example box.  The text in the edit box is appended to each thermodynamic variable.   For example, if the text in the index edit box above were changed from _1 to [1], the example box would then display h[1]=ENTHALPY(Steam,T=T[1],x=x[1]).  Click the Paste button to copy the text in the Example box into the EES Equation window at the cursor position.  



EES Library files are ordinary EES files that have one or more internal functions, procedures, modules and/or subprograms that have been saved with a .LIB filename extension.  Library files that reside in folders within the USERLIB\ subdirectory in the EES application directory or the working directory are automatically loaded when EES starts unless directed otherwise by the Library manager. in the Professional version.  Library files can also be loaded from using the $INCLUDE directive or the Load Library command.  The functions, procedures, and modules in library files are not visible in the Equations Window.  They operate much like the built-in functions.  A single .LIB file can hold one or more Functions, Procedures, Modules and Subprograms.  In this situation, the .LIB file is identified as a folder in the in the list of routines, as seen in the figure above for the Blackbody.Lib file.  Click on a folder icon to view an expanded list of the names of all of the routines contained in the file.  Clicking a second time collapses the view.  Click the View Code button to see the EES code for each routine.


External functions and procedures are dynamically linked library files (DLLs).  These are files written external to EES, but they can be called from within EES.  External functions are generally written in FORTRAN, C or Pascal and are identified with a .DLF filename extension.  There are two formats for external procedures identified with .FDL and .DLP filename extensions.  External procedures written in FORTRAN must use the .FDL format and those written in C or Pascal usually use the .DLP format but they can use the .FDL format as well.   All external functions and procedures found in the USERLIB\ subdirectory and subdirectories within these subdirectories are loaded automatically when EES is started unless directed otherwise by the Library Manager.  External routines in a selected directory can also be loaded manually with the Load Library command or with a $Include directive.  External EES functions and procedures allow the user to add any additional relations, e.g., additional property data.  See the Chapter 19 of the Mastering EES book for additional information on how the user can develop external functions and procedures in C, Pascal, or FORTRAN. 


An example of the selected function will be shown in the example edit box at the bottom of the Function Information dialog.  You can edit the Example box information.  If you click the Paste button, the contents of the Example box will be pasted into the Equations window at the cursor position.