New Version Of NIST Refrigerant Database

NIST (National Institute of Standards and Technology) has released a new version of the NIST Standard Reference Database 23, Thermodynamic and Transport Properties of Refrigerants and Refrigerant Mixtures (REFPROP). Previous versions of this database have become the de facto standard in the refrigeration industry as well as in research labs for providing the property data needed to evaluate new refrigerants and to optimize the energy efficiency of heat pumps and other refrigeration equipment.

Version 6.0 of this database is a complete revision based on the most accurate pure fluid and mixture models currently available. The models are implemented in a suite of Fortran subroutines that have been rewritten completely from earlier versions of REFPROP. Routines are provided to calculate thermodynamic and transport properties for a wide variety of possible input conditions. A separate graphical user interface, designed for the Windows operating system, provides a convenient means of accessing the models.

Among the database's other features are:

• ablity to calculate tables and/or plots for any of 33 pure fluids listed and for mixtures up to five components
• convenience of commercially available refrigerant blends being predefined in the database
• online help system for ease in using the program
• information screens that display fluid constants and documentation for the property models
• numerous options to customize the output.

Database Specifications and Features

Version 6.0 is a complete revision of this database and includes 33 pure fluids and mixtures with up to 5 components, including:

• The environmentally acceptable HFCs, including R23, R32, R125, R134a, R143a, and R245fa
• The HCFCs, including R22, R123, R124, R141b, R142b
• Taditional CFCs, including R11, R12, R13, R113, R114, and R115
• The "natural" refrigerants ammonia, carbon dioxide, propane, isobutane, and 3 other hydrocarbons.

The database boasts the most accurate pure-fluid equations of state currently available:

• High-accuracy MBWR equations of state for 10 fluids, including the international standard EOS for R123
• High-accuracy Helmholtz energy equations of state (new to Version 6.0) for 8 fluids, including international standard equations for R134a and R32 and equations from the literature for R22, ammonia and others
• The Bender equation of state for several of the "older" refrigerants, including R13, R14, R114, and RC318
• An extended corresponding states model for fluids with limited data.

Mixture thermodynamic properties covered:

• Mixture properties are calculated with a new Helmholtz energy model
• Experimentally based values of the mixture parameters in this model are available for 75 mixtures
• Surface tension of pure fluids and mixtures (new to Version 6.0)

Transport properties:

• Viscosity and thermal conductivity are based on fluid-specific correlations (when available) or a new modification of the extended corresponding states model.

A completely new, WindowsTM-based, graphical user interface:

• The fluid or mixture, units, reference state, properties to be displayed (among the 17 available), and other options are specified via pull-down menus
• A wide variety of data tables - in a scrollable, spreadsheet-style format - may be calculated, including saturation properties (with temperature, pressure, composition, or quality as the independent variable) and tables at constant temperature, pressure, density, volume, enthalpy, or entropy (with temperature or pressure varied)
• Sets of independent variables may be read from a file
• Data in any table may be copied to the clipboard for export to other programs (such as spreadsheets)
• Data in any table may be plotted
• Simple pressure-enthalpy and temperature-entropy diagrams and (for binary mixtures) temperature-composition and pressure- composition plots may be automatically generated
• 29 predefined mixtures (such as R407C and R410A) are provided, and the user may define and store others
• Sets of user preferences and entire sessions may be stored for later use
• A complete on-line help system is available.

System Requirements:

• PC running the WindowsTM 3.1, WindowsTM 95 or WindowsTM NT operating system
• Pentium processor (or 486 with math coprocessor)
• 3.8 MB available hard disk space

For more information: Mark McLinden, Physical and Chemical Properties Division, National Institute of Standards and Technology, Boulder, CO 80303. Tel: 303-497-3580. Email: markm@bldrdoc.gov