Copyright: (c) 2005 U.S. Department of Commerce


Index

Click on any item below for additional information on that topic.

General Information

Status Line

Cautions

Menu Commands

File Menu

Edit Menu

Options Menu

Substance Menu

Calculate Menu

Plot Menu

Window Menu

Help Menu

Cautions

Windows

Tables

Saturation Tables

Isoproperty Tables

Specified State Points Tables

Single Point Saturation Tables

Dew and Bubble Point Tables

Plot Window

Programming

DLLs

Excel Spreadsheets

Sample Visual Basic Code

Sample FORTRAN Code

Sample C++ Code

Programming with Delphi

Sample MatLab Code

Sample LabVIEW Code


About REFPROP

REFPROP is an acronym for REFerence fluid PROPerties.  This program, developed by the National Institute of Standards and Technology (NIST) provides tables and plots of the thermodynamic and transport properties of industrially important fluids and their mixtures with an emphasis on refrigerants and hydrocarbons.

REFPROP is based on the most accurate pure fluid and mixture models currently available.  It implements three models for the thermodynamic properties of pure fluids:  equations of state explicit in Helmholtz energy, the modified Benedict-Webb-Rubin equation of state, and an extended corresponding states (ECS) model.  Mixture calculations employ a model that applies mixing rules to the Helmholtz energy of the mixture components; it uses a departure function to account for the departure from ideal mixing.  Viscosity and thermal conductivity are modeled with either fluid-specific correlations, an ECS method, or in some cases the friction theory method.

The property formulations and fluid data files were programmed by:

Eric W. Lemmon, Marcia L. Huber, and Mark O. McLinden

Physical and Chemical Properties Division

National Institute of Standards and Technology

Boulder, CO 80305

ericl@boulder.nist.gov

huber@boulder.nist.gov

markm@boulder.nist.gov

The user interface was written by Eric W. Lemmon.

We gratefully acknowledge the many contributions of our colleagues and associates.  Allan Harvey (of NIST) and Frank Doyle provided very thorough and greatly appreciated debugging of REFPROP.  Arno Laesecke (of NIST) provided an extensive collection of viscosity data.  Lennart Vamling (of the Chalmers University of Technology in Sweden), Johannes Lux (of the German Aerospace Center), and Paul Brown (of Ramgen Power Systems) aided in the MatLab* link.  Chris Muzny (of NIST) aided with the link to C++.   Jay Grassel (of National Instruments), Greg Sussman (of Process Automation Corporation), and Stephanie Outcalt (of NIST) aided with connecting LabVIEW* to REFPROP.

Previous versions of the REFPROP database were developed by Graham Morrison, John Gallagher and Marcia Huber. Jim Ely and Dan Friend wrote the early versions of the related databases NIST12 and NIST14 from which we have extracted algorithms. We thank Sanford Klein and Adele Peskin, the programmers of the original graphical interface implemented in version 6. We had many helpful discussions with Dan Friend, Allan Harvey, Arno Laesecke, Richard Perkins, and Reiner Tillner-Roth.

We also made extensive use of the CATS Database for Pure Fluids and Mixtures of the Center for Applied Thermodynamic Studies of the University of Idaho, Moscow, Idaho; the NIST/TRC SOURCE and TDE Databases, the AIChE DIPPR database, and the Dortmund Data Bank for Pure Component Properties (DDB-Pure), Oldenburg, Germany.  Finally, we acknowledge our many colleagues whose property measurements and models we have taken from the literature, and without which this database would be much reduced in scope.

Development of this software package was supported by the NIST Physical and Chemical Properties Division and the NIST Standard Reference Data Program.  The development of previous versions was supported by the Air-Conditioning and Refrigeration Technology Institute and the U.S. Department of Energy.  Model development and measurements at NIST have been supported over a period of many years by numerous sponsors including the Air-Conditioning and Refrigeration Technology Institute, the U.S. Department of Energy, the Electric Power Research Institute, the Environmental Protection Agency, Oak Ridge National Laboratory, the American Society of Heating, Refrigerating and Air-Conditioning Engineers, and the Building Environment and Physical and Chemical Properties Divisions of NIST.

*Certain trade names and other commercial designations are used in this work for the purpose of clarity. In no case does such identification imply endorsement by the National Institute of Standards and Technology, nor does it imply that the products or services so identified are necessarily the best available for the purpose.


Status Line

The Status Line is displayed at the bottom of the screen.  It displays the fluid name and reference state.  If the settings used to determine the tabular values in the active window differ from the current settings, additional information is displayed showing the settings applicable to the current window.  The reference state for enthalpy and entropy values (selected with the Reference command) is shown last.  Clicking the mouse button on the Status Line brings up the Fluid Information window.


File Menu

The File Menu contains commands to save, retrieve, and print results.  Click on a menu item below for additional information on that topic.

Open

Save

Close

Save Tables

Print

Print Dialog

Print Setup


Open

The Open command reads a file previously saved with the Save command.  The files are identified by a .RFP filename extension.  The Open command restores the program to the state it was in when the Save command was issued.  Thus, the unit system, reference state, properties, fluid, and all tables and plots are restored.


Save

The Save command saves the current state of the program to a file with a .RFP filename extension.  This file can later be recalled with the Open command.  All current information is saved, including the unit system, reference state, properties, property order and fluid as well as all tables and plots.  You will be asked if you want to save when you exit the program if the 'Prompt to save session when closing' option is selected in the preferences.


Close

The Close command deletes all tables and plots from the display, but the program itself continues.  The program will prompt you if you wish to Save all open windows and settings.


Save Tables and Print Tables

The Save Tables command displays a dialog that allows the data in one or more of the current tables to be saved to a file in ASCII format.  The selected delimiter is placed between each value in a row.   Most spreadsheet programs understand the tab character as a separator for items in the same row and a return character to signify the end of the row.  When the data in this format are read from the file into a spreadsheet application, each value goes into a separate cell.  If 'Spaces' is selected as the delimiter, the width of the columns can be specified.

The Print command allows one or more of the tables and/or plots to be printed.  Use the Print Setup command before selecting the Print command if the default printer or printer options need to be changed.

When printing or saving tables, the previously generated tables (and plots when printing) are shown in a list at the left.  Click on the names of the tables or plots you want to print and then click the '>' button (or press the period or '>' keys) to move them from the left list to the right list.   If you click the '>>' button, all of the tables and plots in the left list will be moved.  To remove tables or plots from the selected list, select the names and then click the '<' button (or press the comma or '<' keys).  The tables and plots in the selected list are saved or printed in the order in which they appear in the list.

To save or print the column headings (the property type and units), select the 'Include Column Heading' option.

When saving tables, the 'Full width' option prints one line of the table on one line of the file.  The 'Page width' option formats the tables so that all the properties fit within 80 columns in the file.  The lines are broken up and printed in different sections, similar to that done during printing.


Print Setup and Dialog

The Print Setup command allows the selection of the printer and printer options, such as landscape or portrait formats.  The selected printer and options are applied to the output when the Print command is issued.

The Print Dialog command allows for a few additional options while printing, most important is the 'Print to file' option.  This option sends the output to a file that can then be used in such applications as making PDFs.  Unlike the Print Setup command, the Print Dialog command first displays the menu for selecting tables or plots to print, then activates the dialog menu before printing.


Edit Menu

The Edit menu contains commands to copy and paste information between applications.  Click on one of the following command names for details.

Copy All Table Data

Copy Selected Table Data

Copy Plot

Save Plot Data Points

Paste

Read Data from File

Select All

Insert Row

Delete Row


Copy All or Selected Table Data

The Copy All Table Data command copies all of the information in a table to the clipboard.  The descriptive column headings will be included with the numerical data if this option has been selected in the preferences.

The Copy Selected Table Data command copies the selected section of a table to the clipboard.  If none of the cells have been selected, only the value in the current cell will be copied to the clipboard.  To copy part of the data in a table, select the cells to be copied by clicking in the upper left cell followed by a click in the lower right cell with the Shift key held down (or simply click and drag the mouse).  Selected cells are displayed in inverse video.   Alternatively, use the Select All command to select all of the cells in the table.  Once the desired cells are selected, use the Copy Selected Table Data command to copy them to the clipboard.

Tab characters are used as separators between the values copied to the clipboard.   A return character is placed at the end of each row.  With this format, the selected data can be pasted into most spreadsheet programs and word processors.


Copy Plot

The Copy Plot command copies a selected plot to the clipboard, which can then be pasted into other applications.  The quality of the plot depends on the screen resolution; the copy is only a mirror image of that displayed on the screen.  Enlarging the plot before copying it will produce a higher resolution copy.  For even higher quality outputs, see the Print Dialog command.


Save Plot Data Points

The Save Plot Data Points command will save to a file all of the data points used in generating a plot.  The first column is the x-axis value, the second column is the y-axis value, and the third column indicates whether or not to connect the point with the previous one.  This command is not intended for general use.


Read Data from File

Values can be read from an ASCII file and placed in an open table.  An Open file dialog appears in which you may specify the file containing the independent property values.  The box at the top of the window displays the first 20 lines of the selected file so that you can see the format of the values in the file.  Although only 20 lines are shown, all of the lines are read in when you press the OK button.  Lines in the file that begin with a nonnumeric character, such as *, are treated as comments and are ignored.

Data are read from the file and inserted into the table depending on the inputs under the 'Read column' and 'Insert data into field' options.  The column specified under 'Read column' will be entered into the field specified under 'Insert data into field'.  It is not necessary to read all of the input properties from the file.  For example, you can read the temperature but not the pressure by selecting the blank line (at the top of the drop down box) in the second (and subsequent) rows.

Extra data from the file can be read and placed in a comment column in the Specified State Points table.  The capability to read additional data from a file is useful in comparing experimental and calculated values of a property.  Before this can be done, the 'Add a comment column to tables' option must be specified in the preferences, and a new table containing the comment field must be created.  The comment field can then be specified in one of the boxes under the 'Insert data into field' label.  They can then be plotted along with calculated values.


Paste

The Paste command is used to enter values contained in the clipboard into open tables in the program.  This command is typically used in conjunction with a Copy command from a spreadsheet application.  Paste can be used only in the Specified State Points or Saturation tables.  Values in the same row must be separated by tabs.  A return character must be used to separate data in successive rows.


Select All

The Select All command selects all of the cells in a table.  The selected cells are shown in inverse video.  They can then be copied to the Clipboard using the Copy Selected Table Data command.


Inserting and Deleting Rows

The Insert Row command inserts a blank row into the current table where the cursor is located.   The Delete Row command allows a specified row to be permanently removed from the table.  In both cases, the rows are not renumbered. These commands are accessible only if a window displaying a table is active.


Options

The items in the Options menu allow selection of the unit system, reference state, preferences, properties to be calculated, and the order that the properties are shown in the tables.  Click on the desired command for additional information:

Units

Reference State

Properties

Property Order

Preferences

Save Current Options

Retrieve Options


Units

The Units command will bring up the Unit System dialog in which the units of each property can be specified.  To change the individual units, click on the arrow to the right of the current unit setting.  A drop down list of possible units appears.  Click on the desired unit.  The changes made in this dialog only affect subsequent calculations. The data in existing tables are NOT affected by the changes.

Multiple buttons are available for selecting default sets of unit; for example, standard SI or English units.  Other sets include standard SI units with Celsius for temperature, a mixed set of SI and English units, and an option to use unitless dimensions for some variables, including temperature divided by the critical temperature, pressure divided by the critical pressure, and so on.

Specific (mass) or molar properties can be selected under the 'Properties' section.  When calculating properties of mixtures, the composition can be entered on either a molar or a mass basis, depending on the selection in the 'Composition' section.

Pressures can be expressed as gage pressures by selecting the 'Use Gage Pressure' option.  The atmospheric pressure or elevation at the location of interest is required to use this option.

The units are saved with other preferences when the Save Current Options command is issued.  They are restored to a previously saved option with the Retrieve Options command.


Reference State

When large differences in enthalpy and entropy occur between REFPROP and tables of properties given in handbooks, please note:

The absolute values of enthalpy, entropy, and energy at a single state point are meaningless. It is only the difference between two different state points that matter. Thus, the value for a single state point can be set to any arbitrary value. Many handbooks set the arbitrary state point so that the values of these properties are positive for most liquid or gas states. You can change the values of the arbitrary state points by going to the Options/Reference State menu.  Your choice of options can be permanently saved in the graphical interface by selecting Options/Save Options, and then saving the options under the file name 'defaults.prf'. To change the default in the Excel file, press Alt-F11 to bring up the VB code. If the code does not appear, make sure the project explorer is visible (View/Project Explorer), then click on modules, and then on module1. Then search for the call to SETREF, and change the second input from 2& to 1&. More information on this can be found in your REFPROP\Fortran directory in the file SETUP.FOR under the SETREF subroutine.

The reference states for enthalpy and entropy are entered in the Reference dialog.  There are three common choices for the reference state on which the values of enthalpy and entropy are based.  These three common choices are:

1.  Setting enthalpy and entropy to zero for the saturated liquid at the normal boiling point (designated as NBP).

2.  Setting enthalpy and entropy to zero for the saturated liquid at -40 °C (designated as ASHRAE).

3.  Setting enthalpy to 200 kJ/kg and entropy to 1.0 kJ/(kg-K) for the saturated liquid at 0 °C (designated as IIR).

In addition, the reference state can be set manually by specifying values of the enthalpy (h) and entropy (s) at some arbitrary values of temperature (T) and pressure (P).

When working with mixtures, the default setting can be used for each pure fluid, or the reference state values of enthalpy and entropy can be specified at the currently defined composition.

The exergy reference state and definition can be selected based on the user's preference.

The reference state choices are saved with other preferences when the Save Current Options command is selected.  It is restored to a previously saved option with the Retrieve Options command.


Properties

The properties dialog provides a check box for each of the properties that can be calculated.  If the box to the left of the property name is checked, calculations are done for that property and the values of the property are displayed in the tables.  To select or unselect a property, click the left mouse button in the box.

Most thermodynamic and transport properties can be calculated.  The properties that can be displayed are divided into four categories:  thermodynamic properties, transport properties plus surface tension and dielectric constant, derivatives of the thermodynamic properties including isothermal compressibility and volume expansivity, and special properties.

Thermodynamic properties include temperature (T), pressure (p), density (D), volume (V), internal energy (e), enthalpy (h), entropy (s), isochoric (Cv) and isobaric (Cp) heat capacities, ideal gas isobaric heat capacity (Cp0), ratio of Cp to Cv, speed of sound (w), compressibility factor (Z=p/DRT), Joule-Thomson coefficient (JT=dT/dp at constant h), quality (q=ratio of vapor moles to total moles), 2nd virial coefficient (B), and 3rd virial coefficient (C).  Most of these properties are given on a molar or mass basis, e.g., V=volume/number of moles.  Other properties used more in the chemical industry include the Helmholtz energy (a), Gibbs energy (g), heat of vaporization (hvap), fugacity (f), fugacity coefficients [f(i)/x(i)p], K value (the ratio of the vapor mole fraction to the liquid mole fraction), molar mass (molecular weight), and composition (on either a mole basis or mass basis).

The transport properties include the thermal conductivity (ThC), viscosity (Vis), kinematic viscosity (Vis/D), thermal diffusivity (ThC/D/Cp), and Prandtl number (Vis*Cp/ThC).  The surface tension and dielectric constant are included under the transport properties menu.

Derivative thermodynamic properties include the isothermal compressibility [kappa=1/kt/p= -(dV/dp)/V at constant T], volumetric expansivity (also known as the thermal expansion coefficient) [beta=(dV/dT)/V at constant p], isentropic expansion coefficient (k=w^2*D/p=-V/p(dp/dV) at constant s), isothermal expansion coefficient [kt=D/p(dp/dD) at constant T], adiabatic compressibility [betas=1/k/p=-(dV/dp)/V at constant s], adiabatic bulk modulus [Bs=k*p=-V(dp/dV) at constant s], isothermal bulk modulus (Kt=kt*p=-V(dp/dV) at constant T), isothermal throttling coefficient (-JT*Cp = dh/dp at constant T), and Gruneisen value (dpdT*V/Cv at constant V).  Additionally, properties contained under the derivative tab include most of the common derivatives of density, pressure, temperature, and enthalpy with each other.  The property dp/dT [sat] is the derivative of the vapor pressure with respect to temperature.  The property dh/dZ [sat] is the Waring function (as given in Ind. Eng. Chem., 46:762, 1954) and dB/dT is the derivative of the second virial coefficient with respect to temperature (B is only a function of T).

Special properties include negative reciprocal temperature (-1/T), (Z-1) over the density, exergy (see references about setting the exergy reference state and definition), specific heat input [V(dh/dV) at constant P], Cv in the two-phase region (Cv2phase) (only calculated for pure fluids), supercompressibility factor (Fpv=square root of the compressibility factor at 60 F and 14.73 psia divided by the square root of the compressibility factor at T and p), critical flow factor (the normalized sonic mass flux for inviscid, one-dimensional, steady, isentropic flow), and the internal pressure [T(dp/dT)-p at constant D].  The (Z-1)/D values are best viewed in the diagram menu and are interesting in that the values at zero density are the second virial coefficients and the slope of the isotherms at zero density are the third virial coefficients.  The ideal gas values of density, enthalpy, entropy, Gibbs energy, and Helmholtz energy are also available (note that these are the ideal values at T and p, not the ideal values at zero pressure such as is the case with Cp0).

Within the 'Special' properties tab is the ability to calculate values for metastable fluid states (such as a liquid that has been superheated beyond the saturated state).  These include pressure, enthalpy, entropy, Helmholtz energy, Gibbs energy, and compressibility factor.  For single phase states, the values of these properties will be identical to those calculated under the 'Thermodynamic' properties tab.  However, in the two-phase region, the values given are the metastable fluid states, or more precisely, the properties calculated from the equation of state at the given temperature and density.  The easiest way to generate these values is to calculate an isotherm in the Isoproperty Table command, varying the density.  The two-phase pressure for a pure fluid, calculated from the equation of state, can also be viewed by plotting a p-D diagram with the 'Show 2 phase' option checked.

The 'Bulk, liquid, and vapor properties' option displays three columns for most properties during calculations.  The first column gives the overall, or bulk, value of the property, the second shows the properties of the liquid phase, and the third column gives the properties of the vapor phase.  This is generally useful only when calculating state points within the two-phase region, such as a temperature and a two-phase density.

Several properties can only be calculated at the saturation states, such as the heat of vaporization and surface tension.  Other properties, such as heat capacities and sound speeds, are not available in the two-phase region since they are not thermodynamically defined for two-phase states.  However, the property Cv2phase is available, but its definition is quite different from that of Cv, and the two properties are discontinuous at the saturated state.

The properties are saved with other preferences when the Save Current Options command is issued.  They are restored to a previously saved option with the Retrieve Options command.

References for the equations that calculate all of these properties can be found in the fluid information screen, with one exception:  the dielectric constant.  The equations for this property are documented in:  Harvey, A.H., Lemmon, E.W. Method for Estimating the Dielectric Constant of Natural Gas Mixtures, Int. J. Thermophys., 26(1):31-46, 2005.


Property Order

The property order dialog sets up the order of the properties that will appear when a table is generated.  Select the property that you wish to move, and use the 'Move up', 'Move down', 'Move to top', and 'Move to bottom' buttons to change the property order.  The property order can also be changed by selecting a property with the up and down arrow keys, and then moving the property using the up and down arrow keys while holding down the shift key.

The property order is saved with other preferences when the Save Current Options command is issued.  It is restored to a previously saved option with the Retrieve Options command.


Preferences

The Preferences dialog allows various options to be selected:

If the 'Prompt to save session when closing' option is selected, you will be prompted when the program is terminated to save to a file before closing.  This file can then be retrieved using the Open command when the program is run again.

The 'Prompt before deleting row' option asks for confirmation (after either pressing Shift-del or selecting the Delete Row option while editing a table) before a row is deleted.  A row cannot be recovered after it has been deleted.

The 'Ignore all error messages' option will cause all error and warning messages to be ignored that occur during property calculations.  While this option may relieve you of having to clear each error message, it may cause confusion when properties are not returned after entering inputs out of range or when the program does not converge.  The 'Ignore all warning messages' option will cause all warning messages to be ignored, but will still display the serious error messages.

The 'Copy table headers to clipboard with table data' option can be used to select whether or not the headers at the top of each table are included when copying to the clipboard.

When the 'Show saturation boundaries in tables' option is selected, a blank line will appear between the single and two-phase state points and the boundary between the liquid and vapor phases.

The steam conversion option will use the conversion 1 cal = 4.184 J when not selected, and the conversion 1 cal = 4.1868 J when selected.  The latter value is generally used in the literature only with the calculation of water and steam properties.  The former value (4.184 J) is generally used with all other fluids and mixtures.

In certain applications, such as using Japanese settings with Microsoft Windows, the degree sign, the superscript 2, and the superscript 3 may not be properly displayed, causing unit conversions to not work and displaying units with funny symbols.  In such cases, the nonstandard characters should be turned off (by clicking on the 'Use nonstandard symbols' option), resulting in the loss of the degree signs.  The text '^2' and '^3' will be used in place of the superscript 2 and 3.

The 'Reset bounds when units or fluid are changed' option will reset the starting and ending default values that are displayed when the saturation or isoproperty tables menus are brought up after the units or fluid have been changed.  The values in the plot menus will also be changed to better default values based on the fluid or units selected.  Deselect this option to preserve the bounds that you have set up.

The 'Flip usage of commas and periods in numbers' allows the use of a comma as a decimal point.  For the most part, REFPROP will recognize the user's country settings and this option will not be needed.

The 'Add Notes button to graphs' option will add a small command button in the upper left corner of each plot that allows the user to add notes to a particular graph.  These notes will be printed out under the plot when File/Print is selected.  If this option is deselected, the notes that correspond to each plot will not be lost, but will not be accessible.

The option to 'add a comment column to tables' will add one or more extra columns (up to 10) in each table that can be used to enter comments or user data.  The values in these fields will be ignored, but numerical values can be plotted in the same manner as calculated properties.  Adding text in each field can aid you in labeling each state point, and the size of the comment field can be enlarged as explained in Tables.

The mixture models used in REFPROP vary by type of mixture (i.e., refrigerant vs. hydrocarbon mixtures).  Constituents typically found in natural gas are modeled by the latest GERG model (finished in 2004).   The mixing part of the model (the excess contribution) is similar to that used for the refrigerant mixtures.  The pure fluid equations of state have been shortened and differ from the default equations in REFPROP.  The calculations using these shorter equations are somewhat faster than the default equations, but are slightly less accurate.  If the user wishes to use the shorter equations specified by the GERG-2004 model, the 'Use full GERG-2004 natural gas mixture model' option should be selected.  This will result in slightly different values than the default values.  In either situation, the mixing interaction parameters remain the same.  The documentation for this model is still under review, but will be published as:

Kunz, O., Klimeck, R., Wagner, W., Jaeschke, M. The GERG-2004 Wide-Range Reference Equation of State for Natural Gases and Other Mixtures. GERG Technical Monograph. Fortschr.-Ber. VDI, VDI-Verlag, Düsseldorf, 2006

Calculations from the older American Gas Association program for natural gas mixtures can also be made by selecting the 'Calculate mixture properties using the AGA8 equation'.  This equation is not valid in the liquid phase or in the extended region near the critical point and users of this model should be aware of the uncertainties in the equation in the various regions where they calculate numbers.  The default equations in REFPROP are used to calculate the phase boundaries since the AGA8 model does not allow this calculation.

The 'Use Peng-Robinson equation for all calculations' option switches from the default equations to the less accurate Peng-Robinson equation.  This equation is not recommended for general use in REFPROP.

In addition to these options, the number of digits in the tables can be selected on a global basis, rather than individually selecting the number of digits as described in the Format and Column Position menu.  Changes in the number of digits displayed will be applied to the currently displayed tables if the 'Apply to existing tables' option is selected.  The 'Fixed digits' option allows a fixed number of total digits, including those before and after the decimal point.  The 'Fixed decimal' option allows a fixed number of digits to be specified to the right of the decimal point.  The 'Scientific notation' option allows the number to be displayed in engineering format.

The font size used in the tables can be specified.  The size in previously generated tables will be changed if the 'Apply to existing tables' option is selected.  The label font size used in the graphs can also be modified.

The preferences are saved when the Save Current Options command is issued.  You can restore options at any time with the Retrieve Options command.


Save Current Options

The Save Current Options command brings up a dialog from which a file name can be chosen, identified by a .Prf filename extension.  The file stores the choices made in the Units, Reference State, Preferences, Properties and Property Order dialogs.  In addition, the current fluid, selected with the Pure Fluid, Predefined Mixture, or Define New Mixture commands, and other various settings are stored.

The program reads the Defaults.Prf file at startup.  If you want to change the preferences that appear when the program is started, save your preferences in the Defaults.Prf file.  You can restore options with the Retrieve Options command.


Retrieve Options

The Retrieve Options command brings up a dialog from which a preference file (identified with a .Prf filename extension), previously stored with the Save Current Options command, can be selected.  The Units, Reference State, Properties, Preferences, and Fluid are changed to the specifications in the selected options file.

The Defaults.Prf file is automatically loaded at program startup.   After you have set up the reference state, properties, preferences, and fluid that you would like to use on a general basis, save these options by choosing the Save Current Options command and enter Defaults.Prf as the file name.


Substance

The substance menu holds commands for selecting and defining a fluid.  The current fluid is identified in the Status Line at the bottom of the screen.  The menu options are:

Pure Fluid

Pseudo-Pure Fluid

Predefined Mixture

Define New Mixture

Specify Fluid Set

Fluid Information

Fluid Search

Specify Composition

View Mixing Parameters


Pure Fluid

The Pure Fluid dialog lists all of the pure fluids available.  Select the fluid you want to use by clicking on the fluid name.  Click the Info button to display the Pure Fluid Information dialog, which provides critical constants and other property information for the selected fluid.

If a fluid set has been specified, then the 'All fluids' button will display all of the fluids available, not just those in the specified set.  The pure fluids can be sorted by short name (or nickname), full name, CAS number, full chemical formula, short chemical formula, synonym, or UN number.  This is useful for fluids such as acetone, which is often called propanone, where the name known to the user may not be listed in one of the categories.


Pseudo Pure Fluid

The Pseudo Pure Fluid dialog lists all of the mixtures that are available as pseudo pure fluids.  Select the fluid you want to use by clicking on the fluid name.  Click the Info button to display the Fluid Information dialog, which provides critical constants and other property information for the selected fluid.

The properties that are calculated for pseudo pure fluids are based on equations of state that have been developed solely for the specified composition.  They are generally based on mixture models that were fit to a wide variety of properties at various compositions.  The uncertainties of the pseudo pure fluid equations are often not as good as the corresponding mixture model.  However, the calculational speed will be much higher, especially for saturation properties.


Predefined Mixture

The Predefined Mixture dialog will display a list of the currently defined mixtures available.  A number of predefined mixtures are provided with the program.

You can specify new mixtures consisting of up to twenty pure components using the Define New Mixture command.   Clicking the Info button will bring up the Mixture Information window in which the critical point information, components, and composition of the mixture can be viewed.


Define New Mixture

The Define Mixture dialog provides a means for defining a fluid system consisting of 2 to 20 components.  Select the mixture constituents from the list on the left by clicking on the fluid name, and then on the Add button (or simply double click).  That fluid then moves from the list on the left to the list on the right.  To remove a fluid from the right list, click on the fluid name and then click the Remove button (or simply double click).   The fluids in the right list become part of the selected fluid system.

In addition, multiple selections can be made by either holding down the Ctrl key while selecting multiple fluids, or by holding down the Shift key to mark all fluids between the currently marked fluid, and the selected one.  You can also use the arrow keys to select a fluid, and press Alt-A to add it.  The period and '>' keys will also add a fluid.  Removing the fluid can be done with either Alt-R, a comma, or '<'.  Fluids can be highlighted by typing in the first few letters of their names; for example, pressing 'pr' will select propane; to get propylene, type 'propy'.

These alternate ways of adding fluids make it easier to find and select a fluid.  For example, defining a mixture of R32, R125, R134a, and Propane is quickest by typing the following sequence:  'r3.r125.r134.pr.'  If a wrong letter or number is entered, use the backspace, thus if 'r124' is entered in this example, press the backspace and then a '5', and the program will jump to R125.

Clicking the Info button displays key fixed point parameters for the selected pure fluid.  More information in given in the Fluid Information dialog.

The fluid boxes use the same sorting techniques that were set up in the Pure Fluid dialog and the fluid set defined in the Specify Fluid Set dialog.

After the OK button is selected, the Specify Composition window appears, in which the mass or mole fractions of the components must be specified. In addition, the mixture can be given a name and optionally stored for later use.


Specify Fluid Set

With the increase in the number of fluids contained in REFPROP, it is often desirable to select only a certain number of fluids that the user has interest in.  This is done through the Specify Fluid Set dialog.  Four default sets are available, and can be changed by the user to match their own preferences.  To use one of the four sets, simply click on it and press OK.

To enter a new set, press the Add New Set button and enter a descriptive name.  The Rename button allows you to rename a file set, and the Delete Set button allows you to delete the set.  To specify which fluids are in the set, press the Edit Set button and enter/delete fluids in a similar manner as is done in the Define New Mixture dialog.

The set labeled 'calibration fluids' contains those fluids that generally have both high accuracy equations of state and transport equations.  The user should consult the Fluid Information screen to determine what the actual uncertainties in the equations are.

The sets are saved to the hard drive once you press OK.  There is no need to save the options to keep the changes just made.


Fluid Information

For a pure fluid, this window shows reference information (e.g., the critical temperature), including key fixed point parameters, for the selected pure fluid.  Information on the model, its limits of applicability, and reference citations are provided separately for the equation of state, viscosity equation, thermal conductivity equation, surface tension equation, and melting and sublimation lines by clicking on the tab near the bottom.

The literature citations describing the selected model and the uncertainty of the equation are provided in the box at the bottom.  Some or all of this information can be copied to the Clipboard or sent to the printer by selecting the text and pressing one of the Copy or Print buttons.  Copied information can be pasted into other applications.

If more than one model is available for any of these properties, the list box directly below the box containing information on the range of applicability of the model can be used to select alternative models.  Click on the arrow to the right of the box to display the available models.  The recommended model is identified with the term 'NIST Rec'.  An alternate model may be selected for subsequent calculations by clicking on its name.

When a mixture has been selected, the fluid information screen will display a window containing the mixture name, molar mass (molecular weight), critical properties, and mixture composition.  The mixture composition can be viewed using either mole fractions or mass fractions.  Clicking on a mixture constituent name will bring up the fluid information screen described above for the pure fluid.


Fluid Search

The Fluid Search dialog can be used to find fluids that fit within a range of values.  Either all of the fluids in the database can be searched, or only those in the specified fluid set.  To search for fluids within a specified property range, click on the check box for that property and enter the ranges desired in the unit system displayed.  Multiple properties can be checked simultaneously.  The properties that can be searched include the critical temperature, pressure, and density, the normal boiling point, the molar mass (molecular weight), the triple point temperature, and the liquid density at the normal boiling point.


Specify Composition

The Specify Composition dialog serves two purposes.  First, it provides a means of specifying the composition of a mixture.  The composition can be specified in terms of either mass or mole fractions.  The choice is made by clicking in the box containing the words 'Mass fraction' or 'Mole fraction' followed by clicking on the name of the desired base.  If you click the mouse on the name of a pure component, the Pure Fluid Information dialog appears, providing property information for that fluid.

The mass or mole fractions must be entered for each component and they must sum to 1 (or 100 if percentages are used) if the 'Normalize compositions to one' checkbox is not selected.  If the 'Normalize compositions to one' checkbox is selected, the value of each mass or mole fraction is set to the entered value divided by the sum of the values.  This option is most convenient if you want to specify the composition of a mixture by specifying the mass of each component.

The second function served by this dialog provides an opportunity to store the fluid system so that it can later be selected with the Predefined Mixture command.  The name appearing in the Predefined Mixture window and the status bar at the bottom of the screen is entered in the 'Mixture name' field.  Click the Store button to save this information.

The Add or Remove Fluid buttons allow you to enter or delete fluids in the list without having to start back at the Define New Mixture dialog.  The Add Fluid button will bring up the pure fluid list and the desired component should be selected.  To remove a fluid, put the cursor in the composition box for that fluid and press the Remove Fluid button.  You will be prompted for confirmation before the fluid is removed.

The Copy button places the fluid names and compositions (separated by tabs) onto the clipboard so that they can be pasted into other applications.  The Paste button will paste the values that are on the clipboard into the composition boxes.  The paste function is smart enough to search through multiple columns in the information stored on the clipboard for a column that contains numbers that sum to 1.  For example, the copy button pastes both the fluid names and compositions to the clipboard.  If the paste button is then pressed, the program realizes that the first column does not contain compositions and will paste the second column into the composition boxes.


View Mixing Parameters

The database applies mixing rules to the pure-fluid Helmholtz energies.  In some cases, it may be possible to improve the agreement between the calculated properties and experimental measurements by altering these rules.  However, great care must be used in altering these rules, because they can greatly change the calculated properties.  This command is not intended for the casual user.

The mixing rules are applied to binary pairs of fluids.  It may be necessary to select the pair you wish to alter or view.  The fluids in the currently defined mixture are listed at the left.  Only one pair at a time can be selected.  To change the fluids, simply select a new fluid, and the fluid selected first will be unmarked so that only two will be checked.

Shown at the right is the currently defined mixing rule for the selected binary pair and the associated parameter values.  Different rules can be chosen by clicking on the down arrow button at the right of the rule box.  The parameter values can also be changed.  No error checking is provided on these values, so take care when changing the mixing rules.  Also, note that changing the mixing parameters can change the critical parameters associated with the mixture.

Clicking the Apply button accepts the mixing rules and values as displayed, replacing the stored values.  The binary pair can then be changed so that additional mixing rules can be entered.  The OK button accepts the mixing rules as shown, and closes the dialog.  The Reset button restores the mixing rules for each binary pair to their original (as shipped) state.

At the bottom of the dialog, documentation is provided briefly describing the mixing rule.  You can select part or all of the text in this box.  The Copy button copies the selected text to the Clipboard that can then be pasted into another application.


Calculate

The Calculate menu holds commands for initiating the calculations of thermodynamic and transport properties of the selected fluid.   Several modes of calculations are provided with the following commands.

Saturation Tables

Isoproperty Tables

Specified State Points

Single Point Saturation States

Dew and Bubble Point States

Other items associated with calculating properties include:

Format, Column Position, and Automatic Data Entry

Read File Data

Tables

Information on available properties and their definitions


Saturation Tables

There are several different types of saturation tables.  For a pure fluid, when the Saturation Tables command is selected, the type of calculations to be made is specified by selecting one item from each list displayed.  After the OK button is selected, another window appears in which the range and increment of the property to be varied are specified.  After the second OK button is selected, calculations are initiated and a table displaying the results appears.  The columns are initially shown in a preselected order and with a default format.  The format and column position of each column can be changed by clicking in the column header to bring up the Format and Column Position dialog.

For mixtures, the window contains additional items that allow you a variety of methods for calculating saturation conditions.  The first option in the 'Composition basis' menu calculates state points that are NOT in equilibrium with each other.  The composition of the liquid and vapor state points are the same as that of the specified mixture, and at the specified temperature or pressure.  The second two options calculate properties that are in equilibrium, but that will be at different compositions (except in the case of azeotropes, or azeotrope-like mixtures).  The composition should be displayed (see Properties) to view the full state of the system.  Different properties can be selected to vary in the table.  The first four items that can be selected under the 'Vary' label generate points at the composition of the mixture; the last two items calculate properties at different compositions and have no connection to the composition specified when the system was set up.  The red dots in the example picture indicate which points will be calculated.  The gray lines connect points that will be displayed on the same row of the table.

If the composition of the mixture is to be varied, an additional window will appear.  The temperature is entered at the upper left.  The composition will be linearly varied from the condition indicated in the 'Initial' column to that in the 'Final' column using the number of points indicated at the upper right.  With 11 points, the composition of this binary system is varied from pure component 1 to pure component 2 with increments of 0.1 in mole fraction.

For solid-fluid saturation calculations (sublimation or melting), the properties displayed are the equilibrium fluid phase for either the liquid or the vapor.  Properties for the coexisting solid are not available.


Isoproperty Tables

Two properties must be specified to fix the state of a fluid.  The Isoproperty command allows one of the properties to be held constant while the other is varied in a controlled manner.  After the two input properties are specified and the OK button is selected, another window appears in which the value of the constant property and the range and increment of the varying property are specified.

After the second OK button is selected, calculations are initiated and a table displaying the results appears.  The columns are initially shown in a preselected order and with a default format.  The format and position of each column can be changed by clicking in the column header to bring up the Format and Column Position dialog.

Select the 'Leave active' option to keep this window on top so that multiple isoproperty lines can be generated.  Select the 'Add to current table' option to add the calculated values for each new isoproperty to the bottom of the current table.

Multiple tables (from different windows) can be plotted together by selecting all of  the desired tables (hold down the shift key) in the New Plot menu.


Specified State Points

The blank grid allows you to select two independent properties to fix the state of the fluid.  The remaining thermodynamic and transport properties corresponding to this fixed state will then be calculated.

The values of the independent properties can be entered in three ways (in addition to reading data from a file), as listed below.

1.	Values can be simply typed into the cells of the property table.

2.	Values can be automatically entered in a systematic manner by clicking on the header at the top of the column.  This action brings up the Automatic Data Entry window.

3.  	Values can be pasted into the independent variable cells from another application, such as a spreadsheet.  Copy the values to the clipboard using the other application's Copy command.  Then, click the mouse in the first cell in the REFPROP table and select the Paste command.

Using the Specified State Points Table

Whether the independent properties are read from a file or entered manually, as soon as two valid input properties have been entered, the table will calculate the remaining properties and display them in the appropriate columns.  Note that you can then change the inputs or select new inputs (which causes the calculated values in that row to be erased) and repeat the calculation process.

Saturation or melting line states can be calculated by adding the letters 'l', 'v', or 'm' before or after the value of temperature, pressure, density, enthalpy, or entropy.  Note that 'm' returns liquid properties at the solid-liquid boundary.  REFPROP does not calculate solid properties.  In the case where 'l' or 'v' is entered, and there is only one valid liquid or vapor state point, that point is returned regardless of whether or not it is in the liquid or vapor state.  If a liquid density is entered with a 'v', the liquid state is calculated internally; however, the vapor state is returned.  The same is true for a vapor state entered with 'l'.  The properties at the critical point can be calculated easily by entering 'cr', and the properties at the triple point can be calculated by entering 'tr' (liquid properties can be obtained with 'trl' and vapor properties with 'trv').

For state points that are double valued (see the Cautions menu for more information), the character '<' or '>' can be added to the number (before or after) to find the lower or upper root, respectively.  These same characters can also be used to find metastable fluid states for temperature and pressure inputs.  For example, the saturation pressure for nitrogen at 100 K is 0.778 MPa.  Inputs of 100 K and 0.777 MPa will return a vapor state, but inputs of '100' for temperature and '0.777>' for pressure will return a metastable liquid state.

For mixtures, the composition of the mixture can be entered on a line, but must be done BEFORE the two valid state points are entered.  For convenience, the Specified State Points (varying composition) command can be chosen.  This command places the composition fields at the beginning of the table (and activates them if they were not selected in the properties menu).  The composition fields can be moved permanently by selecting the property order.

The position and format of any column can be changed, if desired, by clicking on the column header.


Specified Saturation States

The blank grid allows you to select either the saturated temperature, pressure, or density to fix the state of the fluid.  The remaining thermodynamic and transport properties corresponding to this saturation state will then be calculated.  For mixtures, the properties of the corresponding phase will be in equilibrium with the specified phase.  The 'Composition' option should be selected (see Properties) to show the composition of the equilibrium phase.

Use the Bubble and Dew Points table to calculate vapor and liquid saturated properties where the phases are at the same temperature, pressure, and specified composition.  The liquid and vapor states in this table are not in equilibrium with each other.

The values of the independent properties can be entered in three ways (in addition to reading data from a file), as listed below.

1.	Values can be simply typed into the cells of the property table.

2.	Values can be automatically entered in a systematic manner by clicking on the header at the top of the column.  This action brings up the Automatic Data Entry window.

3.  	Values can be pasted into the independent variable cells from another application, such as a spreadsheet.  Copy the values to the clipboard using the other application's Copy command.  Then, click the mouse in the first cell in the REFPROP table and select the Paste command.

Using the Specified Saturation States Table

Whether the independent properties are read from a file or entered manually, as soon as a valid input property has been entered, the table will calculate the remaining properties and display them in the appropriate columns.  Note that you can then change the input or select a new input (which causes the calculated values in that row to be erased) and repeat the calculation process.

For mixtures, the composition of the mixture can be entered on a line, but must be done BEFORE the input property is entered.  This can allow you to vary the composition and view the effect while holding temperature or pressure constant.  The composition fields can be moved permanently to the beginning of the table by selecting the property order to make it easier to enter the values.

When entering temperatures or pressures, it is important that the value is placed in the appropriate column.  Placing the temperature in the 'Liquid phase temperature' column will calculate a bubble point with its corresponding vapor state at some equilibrium condition.  Entering the temperature in the 'Vapor phase temperature' column will calculate a dew point with its equilibrium liquid condition.  These two lines will be completely different, and can be confusing if the compositions are not displayed.

The position and format of any column can be changed, if desired, by clicking on the column header.


Bubble and Dew Points

The blank grid allows you to select either the saturated temperature, pressure, or density to fix the state of the fluid.  The remaining thermodynamic and transport properties corresponding to this saturation state will then be calculated.  This menu item is only active for mixtures.  The properties of the two phases will NOT be in equilibrium (see Saturation Tables).  Use the Specified Saturation States table to calculate properties of phases in equilibrium.

The values of the independent properties can be entered in three ways (in addition to reading data from a file), as listed below.

1.	Values can be simply typed into the cells of the property table.

2.	Values can be automatically entered in a systematic manner by clicking on the header at the top of the column.  This action brings up the Automatic Data Entry window.

3.  	Values can be pasted into the independent variable cells from another application, such as a spreadsheet.  Copy the values to the clipboard using the other application's Copy command.  Then, click the mouse in the first cell in the REFPROP table and select the Paste command.

Using the Bubble and Dew Points Table

Whether the independent properties are read from a file or entered manually, as soon as a valid input property has been entered, the table will calculate the remaining properties and display them in the appropriate columns.  Note that you can then change the input or select a new input (which causes the calculated values in that row to be erased) and repeat the calculation process.

The composition of the mixture can be entered on a line, but must be done BEFORE the input property is entered.  This can allow you to vary the composition and view the effect while holding temperature or pressure constant.  The composition fields can be moved permanently to the beginning of the table by selecting the property order to make it easier to enter the values.

The position and format of any column can be changed, if desired, by clicking on the column header.


Format, Column Position, and Automatic Data Entry

The format of the data in each column is set to a default style.  You can change the format of the data in the column by right clicking the mouse in the column header.  This action will bring up a window in which the format of the data in the column and the column position can be changed.

To change the format of the values in the column, click on the arrow to the right of the 'Style' field.  A list of 'Default', 'Fixed digits', 'Fixed decimal', and 'Scientific notation' is shown.  The 'Fixed digits' option allows a fixed number of total digits, including those before and after the decimal point.  The 'Fixed decimal' option allows a fixed number of digits to be specified to the right of the decimal point.  The 'Scientific notation' option allows the number to be displayed in engineering format.  An example illustrating the display format appears to the right of the word 'Format'.  The number of digits to be displayed can be changed globally with the preferences command.

To change the column position, click the up or down arrows until the desired column position is shown.  The positions of all other columns shift accordingly.  To change the column position permanently, use the Property Order command.  The units of the column can be changed using the 'Convert units' option.  For mixtures, unit conversions requiring the molar mass of the fluid are not available.  Note that you may not convert units when using specified state tables; however, the option to clear an entire column is available.

To fill a table with a range of numbers, enter a combination of values into the cells under the 'Specify values' section.  The value to be placed in the first row of the selected row must be specified in the 'First value' field.  Beneath this field are additional input boxes in which the last value in the range, the increment (or a multiplier), or last row can be specified.  If 'Increment' is selected, the value of successive rows in the table is determined by adding the value in the increment field to the previous value.  Similarly, if 'Multiply' is selected, successive values are determined by multiplying the previous value by the value indicated in the field.  If 'Final value' is selected, the variable is varied in uniform increments from the specified initial value to the final value.  In the special case where you wish to fill a certain number of rows with a constant, enter the starting row, the ending row, and the constant in the 'First value' field.  The independent values entered must be in the unit system selected with the Units command.  You can also specify that the values are saturated liquid or vapor states.  This simply adds an 'l' or 'v' to the number as it places it in the field, as described in the Specified State Points dialog.


Tables

Tables can be generated from a variety of options in the REFPROP program, including Saturation Tables, Isoproperty Tables, Specified State Points Tables, Single Point Saturation Tables, and Dew and Bubble Point Tables.  The number of digits displayed, the number format, and the units can be changed by clicking on the column header.  This will display the Format, Column Position, and Automatic Data Entry window.  Also accessible from this window is the ability to generate a sequence of numbers, either in steps or exponentially.

The height and width of the rows and columns can be changed by placing the mouse over the line separating two rows or columns, and dragging the line to a new position.  The column widths are also enlarged in some operations when the width of the numbers in the column exceeds the column width.

Rows can be deleted by pressing Shift-Del or by using the appropriate menu item (see Delete Row).  This action permanently removes the row, and a preference can be set to warn before a row is deleted.

Selecting the contents of the entire table can be done either through Select All or by clicking the uppermost left cell and dragging the mouse.  Clicking the row or column headings selects the entire row or column.  The Copy Selected Table Data command will copy the text to the clipboard.  Text can be pasted into some tables with the Paste command.

An averaged value of a selected set of cells can be obtained by clicking the right mouse button once the cells have been selected.


Plot Menu

The Plot menu provides commands to plot values in any existing table.  In addition, many plots, such as temperature-entropy, temperature-enthalpy, and pressure-enthalpy plots can be generated automatically.  The commands in this menu are listed below.  Click on the command name for more information.

New Plot

Overlay Plot

Modify Plot

Add Label

Zoom In

Zoom Out

Zoom Full Frame

Diagrams

Plotting Data Characteristics

The appearance of the plot window can also be changed by the Plot Window controls.


New Plot

This command generates a new plot window in which the data in a column of a table can be plotted against data in any other column of the same table.  The Overlay Plot command plots data within an existing plot window.

By default, it is assumed that data from the active table will be plotted.  (The 'active table' is the table that was last accessed and is on top of the other tables.)  However, the table from which the data are taken can be selected in the table list at the upper right of the window.  It is also assumed that all of the data in the table are to be plotted.  If this is not the case, it will be necessary to enter the starting and ending row numbers in the 'From row' and 'To row' fields.

Select the variables to be plotted on the x axis and y axis by clicking on their names in the respective lists.  Appropriate minimum, maximum, and interval values are supplied for the selected x and y variables.  However, these values may be changed before the plot is generated by modifying the default values, or later with the Modify Plot command.  Other plot options, such as the scale type, the line type, and the plot symbol, may also be selected in this dialog, or later with the Modify Plot command.

The 'Format' option specifies that the numbers on the axis will be printed in either a fixed format or a scientific format, using the number of digits selected in the second box after the 'Format' label.

Data from multiple tables can be plotted simultaneously by selecting multiple items in the 'Plot data from' list and pressing 'OK'.  You must be careful that the selected items all contain the same columns.  Plotting isoproperty tables and saturation tables together must be done in two steps (once with New Plot, then with Overlay Plot).

Pressing the Set Default button will add the current settings to the Defaults.Prf file.  Subsequent uses of the program will then start with these defaults.  The settings can also be saved by choosing Save Current Options.


Overlay Plot

This command works exactly like the New Plot command except that the additional data will be placed in an existing plot window.  Overlaid plots use the existing scales for the ordinate and abscissa.  However, if the overlaid plot has values that cause part or all of the plot to be off scale, a dialog box is presented that asks if you want to rescale the plot.

See the description of the Plot Window for information on how to modify the appearance of an existing plot.


Modify Plot

The Modify Plot command can be used to change the appearance of an existing plot.  This command can be invoked by either double clicking anywhere within the plot or by selecting the Modify Plot command.  In the latter case, the plot in the active window is affected.

A dialog box appears with controls to modify the color, symbol, and line style of the plot as well as controls to alter the appearance and range of the scales on the abscissa and ordinate.

For plot windows containing more than a single data set, a list of the plotted data sets is provided in the Data list box at the upper right of the dialog.  Select the data set for which the line type, symbol, and color specifications are to be applied.   These changes can be made to one data set at a time or to a multiple selection.  After changes have been made, either the Apply button or the OK button can be selected.  By pressing the Apply button, other changes can be made to other data sets.  The Remove button removes all selected data sets from the plot.

The axis labels can be edited in this window.  Other options in the Modify Plot menu are described in the New Plot menu.


Add Label

The add label window allows text to be placed on a plot window or allows text on a current plot to be modified.  The plot window where the label will be added must be the active window.  The text to be placed on the plot window is entered in the edit field at the top.  Other text characteristics may be entered, such as the font type, font size, and style.  When the OK button is clicked, the text appears at the center of the plot window.  It can then be dragged to any location in the plot by pressing and holding the mouse button down on the text item and then by dragging it to its new location.  The coordinates of the label are displayed if the shift key is held down as well.

The degree character can be entered into the text of the label by pressing Alt-248 (or Alt-0176) on the numeric keypad.  Alt-253 will add a superscript '2' to the text.  Also, Alt-0178 will add a superscript '2' and Alt-0179 will add a superscript '3'.  Other special characters of interest using the Alt key include 225: ß, 230 (or 0181): µ, 241 (or 0177): ±, and 246: ÷.

You can change the characteristics of the text item at any time by double clicking on it.  This window will reappear and allow you to make the changes.  The label can also be deleted.  To delete all labels on a plot, double click one of the labels and select the Delete All button.  See the Plot Window description for additional plot window controls.


Zoom In, Out, Full Frame

There are several ways to zoom in or out of a plot.  The easiest way is to click the mouse on the plot and, while holding down the mouse key, drag to a new location.  The plot will zoom to the locations where the mouse was pressed and then released.  Dragging outside the plot window will increase the plot size to the point where you released the mouse.

You can also zoom in or out by using the commands on the menu bar.  If the Zoom Full Frame option is used, the plot will return to either its original size, or the size that was selected from the last use of the Modify Plot command.


Diagrams

Diagrams can be generated for the selected fluid.  The types of diagrams that can be plotted include:

Temperature vs. Entropy

Temperature vs. Enthalpy

Pressure vs. Enthalpy

Pressure vs. Density

Pressure vs. Volume

Pressure vs. Temperature

Compressibility Factor vs. Pressure

Enthalpy vs. Entropy

Isochoric Heat Capacity vs. Temperature

Isobaric Heat Capacity vs. Temperature

Speed of Sound vs. Temperature

Exergy vs. Temperature

(Z-1)/density vs. density

Viscosity vs. Temperature

Thermal Conductivity vs. Temperature

Temperature vs. Composition (for binary mixtures only)

Pressure vs. Composition (for binary mixtures only)

Each diagram type will allow different combinations.  In the case of a pressure vs. enthalpy diagram, lines of constant temperature, density, entropy, and quality can be displayed.  To specify plotting isotherms, place a check in the box to the left of the label.  You can then specify a range of temperatures to be plotted and/or up to 12 individual isotherms.  In addition, values in the two-phase region can also be plotted.  Generally, this option is not selected, and a straight line is drawn between the saturated liquid state and the saturated vapor states.  For mixtures, showing two-phase values will be very computationally intensive.  When plotting isotherms for a pure fluid, the two-phase option works differently from what might be expected:  values of the metastable fluid states are shown, both real and inaccessible.  However, you should realize that there are virtually no data for metastable states of most fluids, and values shown will be extrapolations of the equations of state.  In addition, calculated values can be extremely large, and plotting these values can result in unexpected plots in the two-phase region.  See the Properties dialog for additional information.

For cases where multipliers are preferred rather than increments in the 'From...To...Step' inputs, the character '*' can be added in front of the step input.  Thus, inputs of 'From:  0.001, To:  1000, Step:  *10' would produce isolines of 0.001, 0.01, 0.1, 1, 10, 100, and 1000.  The More/Less button can be selected to include/exclude additional boxes where property values can be individually added.

The starting and ending values of the x and y axis can be modified.  These values can be changed later with the Modify Plot command; however, some data may not be calculated beyond the ranges indicated in these boxes, and a new diagram will have to be generated with larger bounds.

Labels identifying the isoproperties are automatically generated if the 'Include labels' option is selected.  You can change or delete these text items or add additional text using the Add Label command.  If too many labels are being placed on a plot, the 'Unlabeled lines' option can be used to specify that labels should occur on every other line, every third line, and so on.  The appearance of the plot can be modified with the Modify Plot command and with the controls in the Plot window.

The amount of data calculated, resulting in fine or coarse plots, can be selected in the 'Point spacing' option.  Several additional options are available to control whether the saturation lines are drawn, the melting line is drawn, and the saturated liquid and vapor states are connected by lines.  The 'Swap density for specific volume' option will change the density inputs to volume inputs.  The 'Add s and v lines at saturated temperature' option will draw a vapor phase isochore and a vapor phase isentrope for each isotherm that is plotted, using the value of volume and entropy at the saturated vapor state point.

Once a plot has been generated, other data may be superimposed on it using the Overlay Plot command.

Other diagrams

Other properties can be plotted as well using these same techniques.  Under the 'Axis scaling' label in the plot dialog, the x and y properties can be changed by selecting the down arrows and clicking on the desired property.  Most of the properties available in the Properties dialog can be plotted on the y axis.  Properties allowed on the x axis include temperature, pressure, density, volume, energy, enthalpy, entropy, compressibility factor, exergy, -1/T, and composition.  In order to avoid problems where one of the four columns at the top of the plot dialog matches one the properties on the x or y axis, you should carefully select as a starting point one of the diagrams in the Plot pull down menu that contains your x or y property.  For example, to generate a plot showing the Prandtl number vs. temperature, you could start with a T-s diagram so that the upper four columns show pressure, density, enthalpy, and quality.  If a T-h plot was selected, then the third column would contain entropy instead of enthalpy.  Once this is done, the x axis property should be changed to temperature and the y axis property should be changed to the Prandtl number.  Even better in this case would have been to select a Cv vs. T plot so that temperature is already placed in the x-axis option.  Once the initial plot is setup, you can then go to the Plot/Other Diagrams option to modify your previous settings.


Window Menu

The Window menu contains the following four menu items

Tile

Cascade

Rename Window

Close Window


Plotting Data

There are a number of controls on the plot window:

Change Plot Size

Place the cursor over the bottom right corner of the plot window.  To resize the plot, hold the mouse button down while dragging the lower right corner of the plot window to a different position.

Move Plot Labels

Plot labels can be placed on a plot window with the Add Label command.  The text is initially placed in the center of the plot window, but it can be moved to any position.  To move the text item, place the cursor over the text item.  Hold the mouse down while dragging the text to its new location.

Cross Hairs

Hold the Shift key down to display cross hair lines on the plot.  The coordinates of the cross hairs (in units corresponding to the plot axis) are displayed at the top of the plot.

Zoom

Click and hold down the mouse button to create a box.  When the mouse button is released, the plot within the box will become the new plotting area.

Modify Plot Characteristics

Double click the mouse anywhere within the plot rectangle.  The Modify Plot dialog appears, just as if the Modify Plot command were issued.

Add a Point to a Table

When the right mouse button is clicked within the plotting area, the spot will be marked with a circle, and the values of the properties at the selected state point will appear on the most recently used table (created from Calculate/Specified State Points).  If no table is active, the right mouse button marks the spot with a circle only.  Points added to the plot in this fashion can then be connected with lines or deleted by entering the Modify Plot option.


Tile

The Tile command resizes and positions the existing windows so that all are displayed.  Scroll bars are provided, if needed.


Cascade

The Cascade command will arrange all of the currently defined windows so that their title bars are visible, making it easy to select any of the windows.


Rename Window

Each table and plot window is provided with a default title when it is generated.  You can change the default window title by entering an alternative in the edit space provided.  This title is used in the Save Tables, Print, New Plot, and Overlay Plot dialogs for identification.


Close Window

The active window (data or plots) will be closed when this option is selected.  The window will no longer be available once closed.


Help Menu

The Help menu holds commands for accessing the Help processor.  In addition, a command is provided to display the startup screen, which contains the program version number and other information.

First Time Users

Help Index

Using Help

About REFPROP


First Time Users

The following information describes a procedure for quickly getting the REFPROP program set up and running.  We encourage you to explore the many menu options and the Help file so you can obtain the most from the program.

Upon starting the program, a blank screen appears within the program boundaries with a row of commands at the top.  You should first select the fluid you wish to use by clicking on the Substance command and then on one of the options labeled Pure Fluid, Predefined Mixture, or Define New Mixture.  If you select Pure Fluid, then a dialog appears which lists all of the compounds available in REFPROP.

At this point you may calculate properties (using default settings) or customize the units system and properties displayed.  To calculate, click on the Calculate command and then on the Specified State Points option.  A blank grid appears on which you can enter properties.  Once two inputs have been entered, the other properties in the active row will be calculated if it is a valid state point.  The Saturation Points option is similar to the Specified State Points option except that only one input is needed and the properties will always be at saturation.  Calculating tables is accomplished by clicking on either the Saturation Tables or Isoproperty Tables options.

To select which properties you would like displayed, click on the Options command, then on Properties.  Under the 'Thermodynamic' tab, you can select properties like temperature, pressure, and enthalpy.  Under the 'Transport, Misc.' tab, you can select properties such as viscosity, thermal conductivity, and surface tension.

If you would like to change the units you will use for the calculations, select the Options command, and then click on Units.  The Units screen allows you to change each type individually, or use a set of predefined units.  If you are using English units, you would click on the English button under the 'Reset Units' label.  This dialog also allows you to select whether you will use mass or molar properties, and whether you will use a mass or molar basis to enter the compositions for mixtures.

If you desire to make plots, many predefined plots have been set up for you. For example, click on Plot then on P-h Diagram.  You can then make changes to the dialog that appears and click OK.  A plot will be generated based on your inputs.

All of these commands and those not described here are available in this Help file.  The Index will help you find other information.


Help Index

The Help Index command opens the Help file and displays the index page.  The Help program can also be opened by pressing the F1 key, which will display help relating to the contents of the current window.

The Help file is a hypertext document.  Clicking on a highlighted word displays information on that subject.  You can also click the Search button in the Help program to search for a particular keyword.

The Using Help command provides details relating to the use of the Help program.


Using Help

The Using Help command brings up a window providing general directions and suggestions for using the Help program.  The Help file for this program can be directly accessed with the Help Index command or by pressing the F1 key, which brings up help specific to what is shown in the front window.


DLLs

Several examples are included that show how to access the routines within the REFPROP.DLL file.  These examples are explained in the following sections:

Excel spreadsheet

Visual Basic sample program

C++ sample program

Connecting with MatLab

Connecting with LabVIEW

In addition, users can link directly to the Fortran source code, thus avoiding the use of the dll.

Fortran sample program


Excel Spreadsheets

The REFPROP software includes dynamic link library ('.dll') support that allows a broad variety of applications to take advantage of REFPROP's capabilities.  REFPROP is distributed with front-end software that links Microsoft Excel applications to fluid property functions.

The REFPROP Excel front-end is supplied as a Microsoft Visual Basic module.  Excel automatically incorporates Visual Basic as a macrofunction execution, scripting and interface utility.  When the REFPROP front-end module is imported into an Excel spreadsheet, REFPROP functions become accessible to the user.

The information given below demonstrates the front end usage; however, the user is not bound to this format; rather, the preferred method would be to write one's own visual basic code that calls the DLL directly.  A dedicated module will increase the speed of the application and give the ability to use the REFPROP functions to their fullest.

The following supplementary instructions are intended for users who wish to create and modify their own spreadsheets that utilize the REFPROP functions based on the front-end module.  The Excel application included with the software is called REFPROP.xls and is located in the directory where the REFPROP program was installed.  Sample FORTRAN and Visual Basic files are also included.

Properties are calculated by calling various functions.  For example, the following line would be placed in a cell to calculate the density of argon at 300 K and 10 MPa:

=Density("argon","TP","SI",300,10)

Other properties can be calculated by using any of the following functions:

Temperature

Pressure

Density

CompressibilityFactor

LiquidDensity

VaporDensity

Volume

Energy

Enthalpy

Entropy

IsochoricHeatCapacity (or Cv)

IsobaricHeatCapacity (or Cp)

SpeedOfSound (or Sound)

Quality

HeatOfVaporization (or LatentHeat)

JouleThompson

IsentropicExpansionCoef

IsothermalCompressibility

VolumeExpansivity

AdiabaticCompressibility

AdiabaticBulkModulus

IsothermalExpansionCoef

IsothermalBulkModulus

Viscosity

ThermalConductivity

Prandtl

SurfaceTension

DielectricConstant

MolarMass

EOSMax

EOSMin

MoleFraction

MassFraction

LiquidMoleFraction

VaporMoleFraction

Mole2Mass

Mass2Mole

The first input in the call to the function is the pure fluid name or mixture string.  The file name located in the fluids directory where REFPROP was installed should be used as the fluid name (without the .fld extension).

For mixtures, the fluid names and compositions (in mole fractions) of the constituents in the mixture are placed in a single cell as in the following example for dry air:

nitrogen;0.7812;argon;0.0092;oxygen;0.2096

A more convenient way is to use the CONCATENATE phrase to join multiple cells:

=CONCATENATE(A1,";",B1,";",A2,";",B2,";",A3,";",B3)

where the fluid names are stored in A1, A2, and A3, and the mole fractions are stored in B1, B2, and B3.  The stored mixture files (*.MIX) can also be read by simply replacing the fluid name with the name of the mixture file:

=Enthalpy("R410A.MIX","TD","molar SI",300,5)

The second input to the function is the combination of input properties being sent to the function.  Thus, for a given pressure and temperature, the second input would be "PT" (or "TP", depending on the order in which the properties are sent).  Other valid inputs include the density (D), energy (E), enthalpy (H), entropy (S), and quality (Q).  Valid combinations include: TP, TD, TH, TS, TE, TQ, PD, PH, PS, PE, PQ, DH, DS, DE, and HS.  For saturation states, the second input is Tliq or Tvap for a given saturated temperature, Pliq or Pvap for a given saturated pressure, or Dliq or Dvap for a saturated density.  Liquid properties are returned when these inputs contain "liq" and vapor properties are returned when "vap" is used.

The third input to the property functions defines the units.  This input can be one of the following:  "SI", "SI with C", "Molar SI", "E", "cgs", "mks", "M".  If left blank, the default is SI.  The "SI with C" input can be shorted to just "C".  The units that correspond to these inputs are:

SI:	K, MPa, kg/m^3, kJ/kg, kJ/kg-K, m/s, uPa-s, mW/m-K, mN/m

SI with C:	C, MPa, kg/m^3, kJ/kg, kJ/kg-K, m/s, uPa-s, mW/m-K, mN/m

Molar SI:	K, MPa, mol/dm^3, J/mol, J/mol-K, m/s, uPa-s, mW/m-K, mN/m

mks:	K, kPa, kg/m^3, kJ/kg, kJ/kg-K, m/s, uPa-s, W/m-K, mN/m

cgs:	K. MPa, g/cm^3, J/g, J/g-K, cm/s, uPa-s, mW/m-K, dyn/cm

E:	F, psia, lbm/ft^3, Btu/lbm, Btu/lbm-R, ft/s, lbm/ft-s, Btu/h-ft-F, lbf/ft

M:	K, psia, g/cm^3, J/g, J/g-K, m/s, uPa-s, mW/m-K, mN/m

For example, the following line would be placed in a cell to calculate the density of argon at 100 F and 250 psia:

=Density("argon","TP","E",100,250)

The independent variables in the equations of state used in REFPROP are temperature and density.  If more than one property is needed, it is best to first determine these quantities from the given set of initial inputs, and then determine the other properties.  This will greatly enhance the calculation speed.  This is particularly important when properties for pure fluids that are within the two-phase region are calculated.  For example, to calculate the energy, enthalpy, and entropy given the pressure and quality of a two-phase system, place the fluid name in cell A1, the pressure in B1, and the quality in C1.  Put the following in cells A2 through A5:

=Temperature($A$1,"PQ","SI",$B$1,$C$1)

=Density($A$1,"PQ","SI",$B$1,$C$1)

=Energy($A$1,"TD","SI",$A$2,$A$3)

=Enthalpy($A$1,"TD","SI",$A$2,$A$3)

=Entropy($A$1,"TD","SI",$A$2,$A$3)

The functions LiquidDensity and VaporDensity will return the saturated liquid and vapor densities of a two-phase state.  These densities, along with the temperature, can then be used to calculate all other thermodynamic and transport properties at the saturation boundaries using the functions outlined above.

The inputs "Tmelt", "Pmelt", "Tsubl", and "Psubl" return melting line or sublimation line values.  To calculate the melting pressure for argon at 90 K, enter:

=Pressure("argon","Tmelt","SI",90)

To calculate the melting temperature, enter "Pmelt" as the second input and the melting pressure as the fourth input.

=Temperature("argon","Pmelt","SI",25)

The critical point or triple point is returned in a similar manner via the inputs "crit" or "trip", along with inputs of the fluid name and the units.  The molar mass (molecular weight) is returned using the function MolarMass with an input of the fluid name only.  All of these functions are shown in the REFPROP.xls file.

REFPROP can be permanently linked to EXCEL by following these steps:

(This documentation assumes that the REFPROP files have been installed in the "C:\Program Files\REFPROP" directory.  Other installations require appropriate adjustments.)

First, execute either step #1 or step #2 (#1 is preferred):

1.  An environment variable can be set to specify the locations of the fluid files.  This can be done under Start/Settings/Control Panel/System/Advanced/Environment Variables.  A new variable called RPprefix should be created with a value of "C:\Program Files\Refprop" (or the directory where Refprop is located).  The environment variable for the path (located under "System variables") can also be modified by adding ";c:\program files\REFPROP" to the end so that the file REFPROP.DLL can be found from any location.

2.  From EXCEL open the file REFPROP.xls located in ...\REFPROP.  Open the VB-editor with 'Alt-F11'.  Scroll to the top of the module and read the comments.   Make the necessary directory changes as described.   The lines should look like this:

    .

    .

    Public Const FluidsDirectory As String =  "c:\program files\refprop\fluids\"

    Public Const MixturesDirectory As String = "c:\program files\refprop\mixtures\"

    .

    .

The path marked "c:\..." must point exactly to the location where the REFPROP fluid and mixture files are stored on the user's disk drive.  Scroll down several pages and follow the instructions about specifying the path for the Refprop DLL by replacing all occurrences of "Refprop.DLL" with "C:\Program Files\Refprop\Refprop.DLL".  Quit the VB-editor and return to EXCEL and save REFPROP.xls.

3.  Save the REFPROP.xls file as a Microsoft Excel Add-In (named REFPROP.xla).  The default location will appear as something like ...\Microsoft\AddIns.  The file should be saved in this directory.   Alternatively, do a search on your computer for the *.xla files and put the REFPROP.xla file in with the others.

4.  Open EXCEL with an empty spreadsheet and find under 'Tools' the Add-Ins Manager. Find on the list of available Add-Ins the new entry 'REFPROP AddIns'. Mark it as active and exit the Add-Ins Manager.

5. Now open any EXCEL spreadsheet, go to any cell and type something like:

    =density("water","TP","SI",500,100)

6.  If you need to edit the .xla file after it has been installed, reopen the REFPROP.xls file, edit the VB section, then save it as .xls.  Under 'Tools' go to the Add-Ins Manager and deselect the REFPROP AddIn.  Then save the file again as .xla.

7.  Once the module has been imported into a spreadsheet, the REFPROP functions may be selected by using the pull-down function list.  When editing the formula in a cell, select More Functions from the pull-down list and scroll down the Function Category list to select the User Defined functions.  The argument editor will prompt for REFPROP function arguments as it does for standard Excel functions.


Sample Visual Basic Code

Sample Visual Basic (VB) code is provided that demonstrates the use of VB with REFPROP.  The file is called Sample.bas and is located in the Examples directory where the REFPROP program was installed.  It uses the dynamic link library REFPROP.DLL.  Sample FORTRAN and Excel files are also included.

VB subroutines analogous to all of the FORTRAN subroutines are available. The subroutine names have 'dll' appended to the FORTRAN names (for example, SETUPdll is the VB analog to the FORTRAN subroutine SETUP). The inputs and outputs are the same as the FORTRAN routines, except that additional arguments specifying the length of any string variables are required.

The file Sample.bas consists of subroutine and variable declarations in the first part of the file. These declarations would be necessary for any program. The latter part of the file provides examples of calling the various subroutines. No output is displayed when the program is run because it is intended only to show how the calling routines work.  Comments are given throughout the code describing the various calls and procedures.  Additional details on the subroutines and functions are given in the FORTRAN code included with REFPROP.


Sample FORTRAN Code

A FORTRAN example file, called Example.For, is available to help software developers link new code with the routines used in REFPROP.  The file is located in the EXAMPLES directory where the REFPROP program was installed.  Sample Visual Basic and Excel files are also included with REFPROP.

The program is only intended to show how the calling routines work.  Comments are given throughout the code describing the various calls and procedures.  Additional details on the subroutines and functions are given in the main FORTRAN code included with REFPROP.

The file manual.txt located in the FORTRAN directory gives additional details about compiling the code as well as the batch file used to create the REFPROP.DLL file.


Sample C++ Code

The example C code, called EX_C1.CPP (located in the CPP.Zip file), uses explicit (sometimes called late) linking for the functions in the dll.  All functions exported by the dll have been provided in the header file, REFPROP1.h, for completeness.  All functions exported by REFPROP are in the file PASS_FTN.FOR located the REFPROP\FORTRAN directory.  This sample code was tested with the Microsoft Visual C++ compiler in Visual Studio 2003 (Microsoft 32-bit C/C++ Compiler Version 13.10.3077).  The main issues in mixed-language code compiling are function naming conventions, argument passing, and stack maintenance.  Explicit calling of the FORTRAN functions in the dll allows one to define a function pointer name explicitly.  The _stdcall keyword on the function prototype lets the compiler know how arguments will be passed and which side is responsible for cleaning the stack after the function call.


Progamming with Delphi

General information for using the REFPROP DLL with Delphi:

1) All the variables must be passed by address (not just the output); for example:

type

  T_Chaine10000 = Array[0..10000] of Char;

  T_Chaine255 = Array[0..255] of Char;

  T_Chaine3 = Array[0..3] of Char;

procedure SETUPdll (var nc: Integer;  // number of components

                    var hfiles: T_Chaine10000 ;  // fluid file names

                    var hfmix: T_Chaine255;  // mixture file name

                    var hrf: T_Chaine3;  // reference state

                    var ierr: Integer;  // error message number

                    var herr: T_Chaine255);  stdCall;  // error message string

                    external 'refprop.DLL';

procedure TPFLSHdll(var t: Double;  // temperature [K]

                    var p: Double;  // pressure [kPa]

                    var x: Double;  // mole fraction array

                    var d: Double;  // molar density [mol/L]

                    var Dl: Double;  // liquid density [mol/L]

                    var Dv: Double;  // vapor density [mol/L]

                    var xliq: Double;  // liquid mole fraction array

                    var xvap: Double;  // vapor mole fraction array

                    var q: Double;  // quality

                    var e: Double;  // internal energy [J/mol]

                    var h: Double;  // enthalpy [J/mol]

                    var s: Double;  // entropy [J/mol-K]

                    var Cv: Double;  // isochoric heat capacity [J/mol-K]

                    var Cp: Double;  // isobaric heat capacity [J/mol-K]

                    var w: Double;  // speed of sound [m/s]

                    var ierr: Integer;  // error message number

                    var herr: T_Chaine255);  stdCall;  // error message string

                    external 'refprop.DLL';

2) The software using the DLL must declare x as an array [0..19]; for example:

  x: Array[0..19] of Double;

  // initialization (for nc = 3)

  x[0]:=0.7812;

  x[1]:=0.0092;

  x[2]:=0.2096;

  // calculate d from T and P by calling the DLL

  TPFLSHdll (t, p, x[0], d, Dl, Dv, xliq[0], xvap[0], q, e, h, s, Cv, Cp, w, ierr, herr);

3) hfiles can be initialized with the '|' separator between each component; for example:

  type

    T_Chaine10000 = Array[0..10000] of Char;

  var

    hfiles: T_Chaine10000;

    hfiles_str: String;

  hfiles_str:= 'fluids\R22.FLD|fluids\R152A.FLD|fluids\R124.FLD|';

  StrPCopy(hfiles, hfiles_str);


Sample MATLAB Code

A sample MATLAB file, called refpropm.f90 (located in the MATLAB.Zip file), is available to help software developers link MATLAB with the routines used in REFPROP.  The file is located in the directory where the REFPROP program was installed.  Sample Visual Basic code and Excel spreadsheets are also included.

The program was written by Lennart Vamling at the Chalmers University of Technology in Sweden and modified by Johannes Lux of the German Aerospace Center and is only intended to show how the calling routines work.  To quickly test the sample program:

   1) The REFPROP fluids directory should be located in "C:\Program Files\REFPROP\fluids".

   2) The MATLAB path should include the directory where "refpropm.mexw32", "refpropm.m" and the fluid specific files reside.

Otherwise, if the fluids directory is in a different location, one line in the "refpropm.f90" file has to be changed, and it must be recompiled using the MATLAB mex command. MATLAB must then be configured to work with a suitable FORTRAN compiler. The REFPROP subroutines must also be referenced in the mex command.

With the \REFPROP\MATLAB directory as the current working directory, issue the following command in MATLAB to reference the REFPROP subroutines:

         mex refpropm.f90 ..\fortran\*.for

The REFPROP library for MATLAB was compiled with the version R2006b. Because Mathworks has changed the file extension of external files from .mex to .mexw32 (for 32 bit windows systems), the new interface will not work with MATLAB 6.5. Also, the file refpropm.mexw32 is required to run the interface.

The additional file refpropm.m is only for the help function of MATLAB.  If you type "help refpropm", you will see the content of the refpropm.m file.

Some users of the old interface experienced that the first call gave strange answers, but if they repeated exactly the same call, the second gave the correct result.  This effect seems to be tied to the 6.5 compiler and is no longer an issue when using the 2006 MATLAB program.


Sample LabVIEW Code

Example code is provided to show how REFPROP can be incorporated into LabVIEW.  The VI "Refprop Example" illustrates calculations of saturation properties at a given pressure.  In this case, the SATP and SATT REFPROP routines are incorporated into LabVIEW as dynamically linked libraries (DLLs).  It is important to make sure that the path to the REFPROP installation directory is set correctly.  At present, NIST does not support any LabVIEW code written for use with REFPROP.


Cautions

Users of the REFPROP program should be aware of several potential pitfalls:

If you experience large differences in your expected values of enthalpy or entropy as compared to those calculated by the program, see information on reference states.

The equation parameters for mixtures composed of natural gas fluids come from the 2004 GERG model (see preferences for the reference).  The default pure fluid equations of state in REFPROP are not the same as those used in the GERG model, rather they are more complex with lower uncertainties.  The GERG equations for the pure fluids are shorter, less complex, and faster, but slightly less accurate.  To use the GERG model, as published, choose the corresponding option under Options/Preferences.  The preference screen also has an option to use the AGA8 model for calculations.

The NIST REFPROP program is designed to provide the most accurate thermophysical properties currently available for pure fluids and their mixtures. The present version is limited to vapor-liquid equilibrium (VLE) only and does not address liquid-liquid equilibrium (LLE), vapor-liquid-liquid equilibrium (VLLE) or other complex forms of phase equilibrium.  The program does not know the location of the freezing line for mixtures.  Certain mixtures can potentially enter into these areas without giving warnings to the user.

Some mixtures have components with a wide range of volatilities, as indicated by a critical temperature ratio greater than 2.  Certain calculations, especially saturation calculations, may fail without generating warnings.  Plotting the calculation results may reveal such cases--looking for discontinuities in density is a good check.  Such mixtures, including many with hydrogen, helium, or water, may not have Type I critical behavior, that is they do not have a continuous critical line from one pure component to the other.   The estimated critical parameters specified in the Substance/Fluid Information screen for these types of mixtures are represented by a simple linear combination of the pure component values and are not indicative of the true values.

There are cases where an input state point can result in two separate valid states.  The most common is temperature-enthalpy inputs.  Viewing a T-H diagram will help show how there can be two valid states points for a given input.  For example, nitrogen at 140 K and 1000 J/mol can exist at 6.85 MPa and at 60.87 MPa.  When this situation occurs, REFPROP returns the state with the higher density.  See the Specified State Points section for information on calculating the upper and lower roots.

There are certain properties pertaining only to the saturation line, such as dp/dT.  For most cases, displayed properties at saturation states are those for the single phase on the saturation boundary.  Thus, derivative properties at saturation as well as saturation properties that are given along constant property paths, such as Cv, Cp, or Csat, pertain to their state in the single phase.  Those properties label with a '[sat]' indicate a path along the saturation line.

For pure fluids, when the 'Show 2-phase' option in the plot menu is selected, the generated lines for pressure and temperature represent metastable fluid states and the calculated lines between them.  These are calculations from the equation of state disregarding any saturation states and generally have no physical significance.

Changing the units in the 'Options/Units' menu does not change the units on the tables already created, but only for new tables and plots.

Two equations of state are available for hydrogen to account for the different quantum states of the molecule.  Normal hydrogen should be used in applications where it was created and stored at 250 K or above, or when it was cooled to below 250 K and stored without a catalyst for less than a day. The parahydrogen equation should be used where hydrogen was catalyzed or stored for several days at the normal boiling point (NBP) and used at any temperature within 1 day of storage at the NBP.  Since the rate of conversion between quantum states is dependent on temperature, pressure, and the storage container, these values are only estimates.  For more information, see the Leachman et al. literature reference in the Fluid Information window for hydrogen.