steamtab faq

Contents

• What is SteamTab?
• Can I use SteamTab within my own application?
• Which spreadsheet applications does SteamTab support?
• What are the different formulations for the thermodynamic properties of water and steam?
• What is the difference between the Scientific and Industrial Formulations?
• What is the difference between SteamTab, SteamTab Duo and SteamTab Quad?
• Which formulation(s) does SteamTab use?
• What does IAPWS stand for?
• Do you provide help in developing customized software solutions?

Q: What is SteamTab?

A: SteamTab is a spreadsheet add-in software that provides you with a comprehensive set of thermodynamic and transport properties of water and steam. SteamTab products are seamlessly integrated into the supported spreadsheets. 

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Q: Can I use SteamTab within my own application?

A: Yes. You can use the SteamTab SDK to develop your own applications for either internal or commercial use. The SteamTab SDK, distributed as a set of DLLs, provide you with all of the core steam and water properties that you can call from either C/C++, FORTRAN or Visual Basic.

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Q: Which spreadsheet applications does SteamTab support?

A: SteamTab products work with all 32-bit spreadsheet applications: Microsoft Excel 95/97/2000/XP and Lotus 1-2-3 V97/Millennium for Windows 95/98/NT.

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Q: What are the different formulations for the thermodynamic properties of water and steam?

A: The formulations generally used to obtain the thermodynamic properties of water and steam are:

1. The IAPWS Formulation for General and Scientific Use (IAPWS-95)
   This is the formulation approved by the International Association of the Properties of Water and Steam (IAPWS) in 1995 for general and scientific use. This formulation provides the most accurate representation of the thermodynamic properties of water an steam over a wide range of temperature and pressure.
2. The IAPWS Formulation for Industrial Use (IAPWS-IF97)
   This is the IAPWS approved formulation of industrial and special use. The industrial formulation is based on an approximation of the scientific formulation and is generally used in situations where computational speed is of importance. The IAPWS-IF97 formulation is recommended by the IAPWS be used as the basis for contracts beginning January 1, 1999, with respect to performance test calculations for those machinery and systems using steam . The IAPWS-IF97 replaces the previous IFC-67.
3. The NBS/NRC Formulation (NBS/NRC-84)
   This is the previous standard formulation approved for scientific and general use by the IAPWS in 1984. The work was done by members of the National Bureau of Standards and the National Research Council of Canada.
4. The Industrial Formulation of 1967 (IFC-67)
   This, older, but widely accepted, formulation is based on the 1967 IFC formulation for industrial use. This formulation is also the basis of the ASME Steam Tables, 6th Edition.
5. Keenan and Keyes (1969)
   Probably the most widely known and used Steam Tables authored by J. H. Keenan, F. G. Keyes, P. G. Hill, and J. G. Moore.

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Q: What is the difference between the Scientific and Industrial Formulations?

A: The short answer is that the scientific formulation is a rigorous fundamental equation derived from a large set of experimental data. The industrial formulation, on the other hand, is derived to approximate the scientific formulation within certain tolerance at higher computational speeds.

Now, the more detailed answer.

The scientific formulation, described by the Helmoltz equation of state (EOS) which is explicit in density and temperature, provides the most accurate representation of the thermodynamic properties of water and steam over the complete stable fluid region. The coefficients of the EOS are obtained from a large set of accurately measured data.

The current standard for the scientific formulation was derived by Ing. Prof. W. Wagner of Bochum University in 1995, and is approved by the IAPWS as the formulation for general and scientific use. The previous scientific standard, known as the NBS/NRC-84 formulation, was developed by L. Haar, J. S. Gallagher and G. S. Hell in 1984.

The industrial formulation is a numerical approximation of the scientific formulation. The approximation is further facilitated by breaking up the fluid envelope into several distinct regions. Most of these regions provide properties as explicit functions of temperature and pressure allowing direct caluclations of all derived properties. Thus, for most property values the industrial formulation is computationally faster than the scientific formulation. Although, the issue of computational speed could be moot for the majority of desktop applications using a Pentium 75 or faster CPU. Nonetheless, the industrial formulation will have a definite speed advantage in those applications involving real-time processing of large amount of data such as in process control.

The industrial formulations have the additional advantage of being recognized by most national and international standards-setting committees as a contractual standard of water and steam properties for evaluating the performance of steam equipment or systems.

The current standard of the industrial formulation is IAPWS-IF97, which became effective on January 1, 1999 and displaced the widely used 32-year old IFC-67, which was the basis for the ASME Steam Tables, 6th Edition.

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Q: What is the difference between SteamTab, SteamTab Duo and SteamTab Quad?

A: Simply put,

• SteamTab is implemented with the current international gold standard for the thermodynamic and transport properties of water and steam. This standard, referred as the IAPWS-95 formulation for general and scientific use, is implemented in SteamTab V3.0 for users who demand the most accurate steam property values.
• SteamTab Duo, as the name would imply, contains two sets of steam formulation. Additional to the scientific formation, SteamTab Duo contains the Industrial Formulation. SteamTab Duo V3.0 contains the current industrial formulation of IAPWS-IF97, which is a numerical approximation of the IAPWS-95 correlation, but faster in execution time than the IAPWS-95. IAPWS-IF97 has been accepted by most international and national standard-setting committees (including ASME) as the contractual standard of water and steam properties in evaluating the performance of steam equipment or systems.
• SteamTab Quad contains 4 sets of formulations: both sets of Scientific Formulations – the NBS/NRC-84 and IAPWS-95, and both sets of Industrial Formulations – IFC-67 and IAPWS-IF97.

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Q: Which formulation(s) does SteamTab use?

A: The following table summarizes the different formulations used in our SteamTab products:

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Q: What does IAPWS stand for?

A: IAPWS stands for the International Association for the Properties of Water and Steam. IAPWS is a non-profit organization and you can learn more about them and their activities from their website at http://www.iapws.org

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Q: Do you provide help in developing customized software solutions?

A: Yes. ChemicaLogic professionals are ideally suited in helping you design, develop and implement your customized solutions. We have extensive experience in several design technologies, all major programming languages (and not so major as well) and several operating systems. Please contact us if you need additional information.

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