NIST/ASME Steam Properties

December 2008

The National Institute of Standards and Technology (NIST) uses its best efforts to deliver a high quality copy of the Database and to verify that the data contained therein have been selected on the basis of sound scientific judgment. However, NIST makes no warranties to that effect, and NIST shall not be liable for any damage that may result from errors or omissions in the Database.

© 1987, 1996 copyright by the U.S. Secretary of Commerce on behalf of the United States of America. All rights reserved. No part of this Database may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the distributor.

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.

Microsoft is a registered trademark of Microsoft Corporation; Windows and Windows NT are either trademarks or registered trademarks of Microsoft Corporation.

ACKNOWLEDGMENTS

The stay of S.A. Klein at NIST was funded, in part, by the University of Wisconsin and by a grant from the National Science Foundation under agreement No. 9527385. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the National Science Foundation. The authors would like to thank G.R. Dalton and C.W. Levey for editorial assistance, and C.J. Wardell, M.A. Killeen, M.O. McLinden, G.R. Dalton, C.W. Levey, and our industrial beta testers for their assistance in testing the database.

CONTENTS

1. INTRODUCTION

2. SYSTEM REQUIREMENTS

3. INSTALLATION

4. OVERVIEW

5. OPTIONS AND PREFERENCES

5.1   Specifying Units of Measure
5.2   Choosing Properties to Display
5.3   Miscellaneous Options
5.4   Saving and Retrieving Options

6.  GENERATING TABLES OF DATA

6.1 Saturation Tables
6.2 Iso-Property Tables
6.3  Specified State Points
6.4  Manipulating Data Tables
6.5  Warnings and Errors in Calculating Tables

7.1  Plotting Data from Tables
7.2  Predefined Plots

Appendix A.  SAMPLE SESSION

Appendix B.  INFORMATION ON PROPERTY COMPUTATIONS
Appendix C.  INFORMATION ON WARNING AND ERROR LIMITS
Appendix D.  INCORPORATING STEAM ROUTINES INTO OTHER PROGRAMS
Appendix E.  CONTACTS

1. INTRODUCTION

The thermophysical properties of water are of interest in many industrial and research applications. Official international formulations for water properties are developed and maintained by the International Association for the Properties of Water and Steam (IAPWS). The U.S. national committee for IAPWS is the Properties Subcommittee of the Research and Technology Committee on Water and Steam in Thermal Systems of the American Society of Mechanical Engineers (ASME). In 1995, IAPWS adopted a new formulation for general and scientific use for the thermodynamic properties of water, U.S. rights to which were assigned to the U.S. national committee. NIST has taken the responsibility of putting this formulation, along with those for other water properties, into a software implementation. The resulting NIST/ASME STEAM Properties Database, NIST Standard Reference Database 10, provides water properties in a user-friendly manner over a wide range of conditions. The formulations used to compute all the properties are those adopted by IAPWS (see Appendix B). More information on these formulations may be found at www.iapws.org.

The formulation for thermodynamic properties implemented here should not be confused with the separate "Industrial Formulation" (known as IAPWS-IF97) adopted by IAPWS in 1997.  IAPWS-IF97 is designed specifically for use in the steam power industry; it is slightly less accurate than the formulation used here, but is computationally faster. In the U.S., software implementing IAPWS-IF97 is distributed by the ASME; further information may be obtained by contacting them at infocentral@asme.org.

2. SYSTEMS REQUIREMENTS

The STEAM database is designed to run on any personal computer capable of running Microsoft^® Windows™ 98, 2000, NT, Me or XP™. A hard disk with 20 megabytes of available space is also required

The database is available in the following disk format:CD-ROM

3.  INSTALLATION

Start the installation by either double-clicking on the install file SETUP.EXE on the CD via the Windows Explorer or My Computer, or by clicking on the Start button, selecting Run and entering the appropriate location for the installation file e.g. D:\SETUP.EXE (if the CD-ROM drive is assigned the letter D:).

Follow the remainder of the Installation instructions.

If you have purchased a version with source code, it will also be installed by default if you down loaded the installation from the web. Otherwise the code will not be installed, but can be copied of the accompanying floppy.

To start the program, go to the start button, Programs, NIST, and click on steam.

4.  OVERVIEW

When the database is started, an informational window appears as shown in Figure 1.

Figure 1.  Introductory informational dialog box.

NOTE: The figures in this manual show windows and dialog boxes as they appear in the Windows 95 operating environment. If you are in another environment (such as Windows 98), their appearance may be slightly different.

You canCLICK the Information button to get more information on the database (via the on-line Help system). CLICKING the Continue button places you in the environment of the database itself.

The application window appears as shown in Figure 2.

Figure 2.  Main STEAM window.

To begin using the database, simply choose the appropriate item from the menu bar. Some of the menu options (File, Edit, Window, and Help) exhibit few, if any, differences from those options in other applications under the Windows environment. Features that are unique to STEAM are explained in the subsequent sections.

The normal course of action is first to choose units of measure and the desired properties to display; both of these are under the Options menu. Then you choose the type of calculation to perform under the Calculate menu. After performing the calculations, you might want to plot some of the results or to transfer them to another application. The sample session in Appendix A illustrates some of the basic features.

5.  OPTIONS AND PREFERENCES

Under the Options menu, you can choose the units of measure you want to work in, the properties you want to display in calculated tables, and some miscellaneous options. All of these options can be saved for use in a later session.

5.1   Specifying Units of Measure

Selecting the Units item in the Options menu brings up the dialog box shown in Figure 3.

Figure 3.  Dialog box for selecting units of measure.

Choose the unit of measure to be used for each dimensional quantity in the database by picking the appropriate item in the corresponding list box. At any time you can CLICK the SI or English buttons to reset all the units to either of those predefined sets. You can also choose to have properties that are reported per quantity of fluid displayed on a per mass basis (the default), or a per mole basis. The size of the molar basis is governed by the selection in the Mass list box; selecting "g" uses the standard mole, selecting "kg" uses a kilomole, and selecting "lbm" uses a pound mole.

A change in units of measure is only applicable to calculations in tables generated after the change is made. Existing tables are not affected, and further calculations in an existing table continue to use the set of units in effect when that table was first generated.

5.2   Choosing Properties to Display

Figure 4.  Dialog box for selecting properties to display.

Each of the tabs on the dialog displays a related group of properties; you can choose the properties to be displayed in tables of calculated values by checking and unchecking the corresponding boxes. By default, the properties selected are those shown in Figure 4, as well as the viscosity, thermal conductivity dielectric constant, and surface tension. As with the Units selection, changing the properties displayed does not affect tables already in existence.

Selecting the Preferences item in the Options menu brings up the dialog box shown in Figure 5.

Figure 5.  Dialog box for selecting miscellaneous preferences.

The selection "Copy table headers to clipboard with table data" (unselected by default) places the text in the column headers (both the property name and its units) on the Clipboard, along with the selected data in that column, when you choose Copy from the Edit menu. You should not enable this option if you intend to paste the data into the Selected State Points table, which does not accept text.

The selection "Prompt to save tables and plots when closing" (unselected by default)  presents a dialog box allowing you the opportunity to save the window contents to a file before a table or plot window is deleted.

The selection "Add saturation boundaries for isotherms and isobars" (selected by default) causes the saturated liquid and saturated vapor conditions, separated by a horizontal line, to be added to these tables if the range of conditions specified crosses the phase boundary. This is described in Section 6.2.

The selection "Use Enter key to perform calculations for Specified State Points tables" (unselected by default) allows the Enter key to be used to trigger calculations in the tables described in Section 6.3. Normally, the Enter key merely moves the focus to the next row, and one must push the "Calc" button to perform calculations.

The final option in the Preferences dialog allows you to specify the number of digits for the display of all columns of all subsequent tables. This is a shortcut to the normal way of changing the data format by clicking on the heading of each column as described in Section 6.4, which also describes the interpretation of the "digits" value in fixed and floating-point formats. This option can also be applied to existing tables by selecting the check box underneath the field specifying the number of digits.

5.4   Saving and Retrieving Options

The Save Current Options command brings up the usual Windows file save dialog box from which a file name for the current option file can be chosen. Options files are identified by a .PRF filename extension. The choices made in the Units, Properties, and Preferences dialog boxes can be stored in these files. The database reads the DEFAULTS.PRF file at startup. If you want to have the currently selected options appear when the database is started, save them in the DEFAULTS.PRF file. You may save different sets of .PRF files for different uses of the database.

Any set of preferences can be loaded by retrieving the corresponding .PRF file using the Retrieve Options command.

6.  GENERATING TABLES OF DATA

The main use of the STEAM database for most users is the generation of property values at specified conditions. These properties are presented in tables. You can generate tables (up to a maximum of 1500 rows) corresponding to saturation conditions, a fixed value of some property, and individual values of two independent variables. All of these calculations are accessed from the Calculate menu.

6.1 Saturation Tables

Selecting the Saturation Tables item in the Calculate menu brings up the dialog box shown in Figure 6.

Figure 6. Saturation Tables dialog box.

Vapor-liquid, solid-liquid (melting), and solid-vapor (sublimation) calculations are available.  You may vary either temperature or pressure; for vapor-liquid saturation you may also vary the quality (vapor fraction) at a fixed temperature or pressure.  A picture in the dialog box represents the type of calculation chosen.  Once you make your selections and click OK, the next dialog asks you to choose a range of conditions to use in the saturation calculations.  An example for vapor-liquid saturation at specified temperatures is shown in Figure 7.

Figure 7. Dialog box for choosing points at which to perform saturation calculations.

For vapor-liquid saturation calculations at fixed temperature or pressure, the resulting table displays the values of each property in the two coexisting phases.  For properties (such as fugacity) that are equal in the two phases, only one value is shown.  When quality is varied, values for the two-phase mixture are shown; properties not defined in the two-phase region are indicated by an entry of "not applicable".  Figure 8 shows a portion of a vapor-liquid saturation table.

Figure 8. A portion of a vapor-liquid saturation table.

For solid/liquid or solid/vapor saturation calculations, the database computes the location of the fluid/solid boundary, but computes properties for only the fluid phase at that boundary. In addition, the database computes the ice form that is in equilibrium with the fluid. Note that for the liquid-solid boundary at a specified temperature, multiple solutions are obtained for some temperatures because the phase boundary between the liquid and Ice I goes down in temperature as the pressure rises. However, as the pressure continues to rise, the equilibrium solid phase then becomes Ice III (and eventually other forms), for which the temperature of the phase boundary goes back up.

Figure 9 shows a portion of a liquid-solid saturation table.

Figure 9.  A portion of a liquid-solid saturation table.

6.2 Iso-Property Tables

Selecting the Iso-Property Tables item in the Calculate menu brings up the dialog box shown in Figure 10.

Figure 10.  Iso-Property Tables dialog box.

You can choose which property to hold constant, and whether the pressure or temperature is varied. Combinations that are not single-valued are not allowed. This restriction means that in some cases the selection of a property to hold constant causes either the temperature or pressure button in the "Vary" group to be disabled.

Once you click OK on your selection, a dialog box appears, such as that shown in Figure 11.

Figure 11. Dialog box for choosing points for iso-property calculations.

You then choose a fixed value of one variable and a range of values for the other variable.

The resulting table (Figure 12) is similar to that described in the previous section. One additional item, not in the saturation tables, is the Quality (see Appendix B) which in the two-phase region varies from 1.0 for saturated steam to 0.0 for saturated liquid water. For two-phase states, the values displayed for properties that are different in the two phases (such as density) are overall (bulk) values for the two-phase mixture. In order to get values for the coexisting phases, you must compute a saturation table. Some properties (such as the speed of sound) diverge or are not defined in the two-phase region. For these properties "not applicable" is displayed.

Another feature, unique to Iso-Property tables, is triggered when an isotherm or isobar is computed that crosses the vapor-liquid phase boundary. In this case, extra computations are performed at the saturation boundary, and additional rows in the table are added for the saturated vapor and saturated liquid conditions at the boundary. A double-thickness line in the table denotes the phase boundary.

Figure 12 shows part of a table generated for an isobar. This feature may be disabled by unselecting the appropriate check box in the Preferences dialog box, as described in Section 5.3.

Figure 12.  A portion of a table for an isobar.

6.3 Specified State Points 

Selecting the Specified State Points item in the Calculate menu brings up the dialog box shown in Figure 13.

Figure 13.  Specified State Points dialog box.

Here you can choose among several combinations of independent variables for your calculations. Some combinations, such as those which do not make sense, are unavailable. Once you choose one variable, the check boxes corresponding to other variables that are not available in combination with the chosen variable are automatically disabled. In this window, you can also specify the maximum number of separate state points for which calculations are made, thus limiting the number of rows in the resulting table.

Once you CLICK OK in this dialog box, you transfer to the window shown in Figure 14 (for a selection of temperature and pressure as independent variables).

Figure 14.  Specified State Points table before data entry.

This window has two columns in which you specify values of the selected independent variables. An exception occurs if one of your selections in the previous dialog box was "vapor-liquid saturation," in which case only one column is available for data entry. To enter data, CLICK in any of the cells that say "Enter value" and type in the desired number. To enter a set of regularly incrementing values without typing, CLICK on the arrowhead at the top right of the column in which you want to enter data. The result is a dialog box such as the one shown in Figure 15.

Figure 15.  Dialog box for automated entry of independent variable in Specified State Points table.

In this dialog box, you specify numbers in specific rows starting at a given value and increasing or decreasing evenly either to some final value, or by some fixed increment, or by a fixed multiplying factor. You can also clear out existing values.

You can paste values in the "Enter value" cells from the clipboard. These values might have been copied from another table in STEAM or from another Windows application.

When all the points are specified, click the Calculate button, and the table fills with calculated values. If you do not fill in the independent variables for some row, that row is skipped. Points in the two-phase region are handled as described in Section 6.2.

Figure 16 shows part of a Specified State Points table after the computations have been performed.

Figure 16.  A portion of a Specified State Points table after calculations.

You can change the value(s) for any independent variable and then recalculate the properties by CLICKING the Calculate button again. The database recalculates those points for which independent variables have changed.

6.4 Manipulating Data Tables

You can reformat the above tables to suit your needs, by rearranging the columns, and you can change the display format of the numbers in any column. Both of these features are accessed by CLICKING> on the column heading, which brings up a dialog box such as shown in Figure 17.

Figure 17.  Dialog box for moving or reformatting columns.

To change the formatting of the numbers, make a selection in the "Style" list box. In addition to the default format, you can specify display of a fixed number of digits after the decimal point, or display as a floating-point number in exponential notation with a specified number of digits after the decimal point. An example of the currently chosen format is displayed above the Style list box.

You can also move the columns in the table. This is convenient if you want to look at two properties that would normally require scrolling the table between widely separated columns. To move a column, you specify the new column number and click OK. The number of digits displayed may be reset globally in the Preferences dialog as described in Section 5.3.

You can delete a row from a table by choosing the Delete Row command from the Edit menu. This command operates on the table that is currently the topmost window. A dialog box (shown below) asks you to specify the row to be deleted. Note that a row cannot be recovered after it is deleted.

Figure 18. Dialog box for deleting a row.

6.5 Warnings and Errors in Calculating Tables

It may happen that you specify one or more conditions for calculation that turn out to be impossible or outside the valid range of the property correlations used. The database displays two different kinds of warnings in such situations, depending on the severity of the problem.

If you request a calculation that the database cannot perform at all (for example, calculation of vapor-liquid saturation at a temperature above the critical temperature), you get a dialog box such as shown in Figure 19.

Figure 19.  Example dialog box for error condition.

If you answer "Yes," the database skips the point which generated the error and attempts to calculate any remaining points. If you answer "Yes to All," the warning will be suppressed if it occurs for any of the remaining points in the calculation. If you answer "No," the database does not attempt to calculate subsequent points. In any case, points that were successfully calculated are displayed in the resulting table.

It may happen that you request a calculation at a condition for which, while the database can generate an answer, a warning is generated. Warning conditions are documented in Appendix C. An example is the property calculations for a supercooled liquid state when the equilibrium state would be a solid phase. In these cases, the database performs all its calculations. At the end, a dialog is displayed such as that shown in Figure 20.

        

Figure 20.  Example dialog box for warning condition.

In the table itself, the rows that generated warnings are shown in italics. (The entire row is in italics, even though the warning might be generated only because of one property for which the correlation is out of range.) If you click on the row number at the left edge of the table, the warning messages for that particular row are displayed in a dialog box such as that shown in Figure 21.

  

Figure 21.  Example dialog box displaying warning messages.

7. PLOTS

The STEAM database allows you to plot data you have calculated and also create plots in two predefined formats. While these simple plotting capabilities are adequate for many purposes, the database is not intended to duplicate the features of programs devoted to plotting and data analysis. If you want to make publication-quality plots or perform manipulations on the data, we recommend that you transfer the data from STEAM to such a program. Section 10 of this manual describes how to transfer data to other programs.

7.1 Plotting Data from Tables

Once you have calculated one or more tables, you can choose the New Plot item from the Plot menu, bringing up the dialog shown in Figure 22.

                                

By default, it is assumed that data from the topmost table window are to be plotted. However, the table from which the data are provided can be selected using the drop-down table list at the upper right. It is also assumed by default that all of the data in the table are to be plotted. If this is not the case, it is necessary to enter the starting and stopping row numbers

The variables to be plotted on the X and Y axes are selected by clicking on their names in the respective lists. Appropriate minimum, maximum, and interval values are supplied as the X and Y variables are selected. However, these values can be changed before the plot is generated by modifying the default values. Other plot options, such as the scale type, the line type, and the plot symbol, can also be selected in this dialog. The smoothing option fits a cubic spline through the data to produce a smooth curve.

The Modify Plot command, available only when one or more plots have already been generated, allows you to change features of an existing plot. Figure 23 shows the Modify Plot dialog box.

Figure 23. Modify Plot dialog box for changing features of existing plot.

Most of the formatting options are identical to those in the New Plot dialog. In addition, you can change the labels on the X and Y axes by typing in the appropriate edit fields or change the font size for the axis labels. You can also delete individual curves from the plot.

You can plot additional data on existing plots by choosing the Overlay Plot command from the Plot menu. The resulting dialog box is identical to the New Plot dialog shown in Figure 22, except that the axis formatting cannot be specified since it is determined by the existing plot. If some of the new data are outside the range of the existing plot, you are prompted about rescaling the axes. It is the user’s responsibility to ensure that plots are not overlaid in meaningless combinations. In particular, the quantities in the individual data sets plotted should have the same dimensions.

Once a plot is made, it can be resized by using the mouse to move the lower right-hand corner. You can move it around in the plot window by CLICKING on any other part of the plot and moving the mouse. You can see crosshairs and values corresponding to the X and Y positions of the mouse by depressing the Shift key while the mouse is over the plot. (Use the Shift key to toggle this feature on or off.) Finally, DOUBLE-CLICKING on the plot enters the Modify Plot dialog, shown in Figure 23.

You can also add labels to a plot by selecting Add Label from the Plot menu.  Figure 24 shows the Add Label dialog in which you may specify the text of the label and choose its size, typeface, and orientation. This dialog can also be used to edit an existing label; simply double-click on the label. Pushing the Delete button will delete the label currently being edited.

Figure 24. Dialog box for adding a label to a plot.

7.2  Predefined Plots

Two special plots are predefined and can be generated on command from the Plot menu: the temperature-entropy (T-s) and pressure-enthalpy (P-h) diagrams. Both plots allow you to define a number of constant-property lines (isobars on the T-s plot, isotherms on the P-h plot) to be plotted. Default values are given, but you can override them. The saturation boundary is automatically plotted. Figure 25 shows the dialog box defining isobars for a T-s plot.

    Figure 25.  Dialog box for defining a T-s plot.

Once the plot is made, it can be modified with the Modify Plot command.

8. ON-LINE HELP

On-line help is available under the Help menu. The Help Index selection gives an index from which explanations of how to use all the database’s functions can be reached. The Using Help selection explains how to use the Help system itself. The About selection takes you to the same informational window that appears when the database starts.

You can also access Help from an individual dialog box. If you press F1, you are placed in the Help system at the point containing instructions for the use of that dialog box.

9.SAVING YOUR WORK

You may wish to save some calculated tables or plots and come back to them later for further work. This is done with the Save Session command in the File menu. The Save Session command allows you to give the saved session a name by which you can retrieve it later. These saved sessions are identified by a .STM file extension. All information from the currently active session is saved; not only the tables and plots but also any Units, Properties, and Preferences set under the Options menu.

You can retrieve a previously saved session with the Open Session command under the File menu. This command is only available if no tables or plots are currently open; if some are open they must be closed (either individually or by using the Close Session command, see below) before another session can be opened.

The Close Session command (also under the File menu) closes all tables and plots. If the "Prompt to save tables and plots when closing" item is selected in the Preferences (see Section 5.3), you will be prompted as to whether you want to save the current session for later retrieval. Any settings of Units or other options are retained and will still be in effect if you do further calculations. If you wish to recover the default options, you can retrieve the DEFAULTS.PRF file as described in Section 5.4.

You can also save your work in other formats by transferring the data to other applications or saving it to disk; that is described in Section 10.

10. EXCHANGING DATA WITH OTHER APPLICATIONS

You can copy and paste data from tables both within the NIST/ASME Steam Properties Database and between the database and other applications. To select a block of data in a table, CLICK the cell at one corner of the block you want to select. Then press SHIFT and CLICK at the diagonally opposite corner of the block. You can also select a block by dragging the mouse over it while depressing the Shift key. [NOTE: This is similar to selecting cells in most spreadsheet applications, except that in this database you must hold down the Shift key.] You can also select the entire table by choosing the Select All item from the Edit menu. Once a block is selected, you can copy it onto the clipboard by using the Copy Table Data command under the Edit menu. It is then available to be pasted into another table or application. Only the digits displayed in the table are copied; additional precision beyond that displayed is lost. You can also copy a plot onto the clipboard by CLICKING on it and selecting Copy Plot.

You can also save tables (as ASCII text) to a file by choosing the Save Tables command under the File menu. The resulting dialog prompts you to specify the tables to be saved, whether to include the column headings, and what to use as delimiters between columns. You are then prompted for the filename in which to save the table. This feature is useful if you want to transfer information to another application at a later time.

If you have purchased STEAM in a form that includes the source code, you can use the calculation routines from the STEAM database directly inside your own program or build them into a dynamic link library (DLL) to be called from another application. Instructions for how to do this are given in Appendix D.

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