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The program FLUIDCAL is designed for the calculation of thermodynamic properties from equations of state (fundamental equations in the form of the Helmholtz energy) in research and technical applications. This program enables the user to calculate more than 20 different thermodynamic properties of more than 60 substances. For a large number of substances the most common transport properties can also be calculated (see the list of substances for details). As input values for the calculation, every possible combination of the properties temperature T, pressure p, density ρ, specific enthalpy h, and specific entropy s can be chosen.
Available Substances in FLUIDCAL
In order to cover a broad variety of substances, those reference equations of state established at the Chair of Thermodynamics of the Ruhr-Universität Bochum (Prof. Dr.-Ing. W. Wagner) have been supplemented by highly accurate equations of other authors.
At present, software for 69 substances is available:
A detailed overview over the integrated equations of state, including references, is given in this list.
| T | Temperature |
| p | Pressure |
| ρ | Density |
| h | Specific enthalpy |
| s | Specific entropy |
| cp | Isobaric heat capacity |
| cv | Isochoric heat capacity |
| w | Speed of sound |
| u | Specific internal energy |
| f | Specific Helmholtz energy |
| g | Specific Gibbs energy |
| f* | Fugacity |
| (∂p/∂T)ρ | Partial derivative of pressure with respect to temperature at constant density |
| (∂p/∂ρ)T | Partial derivative of pressure with respect to density at constant temperature |
| (∂ρ/∂T)p | Partial derivative of density with respect to temperature at constant pressure |
| μ | Joule-Thomson coefficient |
| δT | Isothermal throtteling coefficient |
| κ | Isentropic exponent |
| B | Second virial coefficient |
| C | Third virial coefficient |
| η | Dynamic viscosity+ |
| ν | Kinematic viscosity+ |
| λ | Thermal conductivity++ |
+ Only available for those substances dynamic and kinematic viscosity can be calculated.
++ Only available for those substances dynamic and kinematic viscosity and the thermal conductivity and Prandtl number can be calculated.
Input values for the calculation
Fundamental equations expressed in the form of the Helmholtz energy usually need temperature T and density ρ as input values to calculate thermodynamic properties. Due to the fact that in technical applications different input values are given in most cases, the program FLUIDCAL contains iterations with which input values of the combinations (T,p), (T,h), (T,s), (p,ρ), (ρ,h), (ρ,s), (p,h), (p,s) and (h,s) can be handled in the homogeneous region as well as in the vapour-liquid two-phase region. These iterations calculate the missing values of temperature T and density ρ with which all other properties can be calculated.
For the most important input values (T,p) and (T,ρ) it is possible to calculate directly all properties listed above. To avoid a complex number of functions, the program contains routines for the direct calculation of the temperature T and density ρ from all combinations of input values. Combined with these functions, all other properties listed above can be calculated depending on every possible combination of input values. In the two-phase region the program calculates the stable two-phase-system values for those properties listed in the table above.
On the vapour-liquid phase boundary the properties temperature, pressure, and density can be used as input values. The most important thermodynamic properties can be calculated directly on the saturated-liquid and saturated-vapour phase boundary depending on temperature. It is possible to calculate all other properties on the phase boundary by combining the functions for the evaluation of the saturated-liquid and saturated-vapour density and the corresponding functions for the calculation of the desired property depending on temperature and density. If for a certain case the vapour pressure is given, functions for the calculation of the saturation temperature and the saturated-liquid and saturated-vapour density depending on pressure are implemented. It is also possible to calculate directly the saturation temperature depending on the saturated-liquid or saturated-vapour density.
Versions of the program FLUIDCAL
The program FLUIDCAL is available in two versions:
As the Windows based interactive program ThermoFluids
The program FLUIDCAL (DLL) for the calculation of thermodynamic properties
To easily integrate the fundamental equations in Windows based standard programs, the FLUIDCAL contains a dynamic link library (DLL). The DLL contains more than sixty functions that allow the calculation of the properties listed above for the single-phase region, within the vapour-liquid two-phase region (if thermodynamically reasonable), and along the saturated-vapour and saturated-liquid phase boundary for all combinations of the input variables T, p, ρ, h, and s. The call is made via simple functions whose names are based on the property to be calculated and the given input variables. Thus, the density ρ for given values of temperature T and pressure p is calculated from the function DOTP.
In addition to the DLL, the Package contains an Add-In file that allows a simple integration of the DLL into Microsoft Excel and Visual Basic. The calculation of the enthalpy h depending on temperature T and pressure p will be done by the function HOTP(T,p,SUBNR). SUBNR defines in this case the substance for which the enthalpy should be calculated. The following figure exemplifies the calculation of the density for the substance methane (substance number 1) in Microsoft Excel.
Similar to this example, all other properties can be called in Excel by integrating the Add-In and directly using the names of the functions.
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Call of functions from the FLUIDCAL DLL with the help of an Add-In in Excel. |
Moveover, the Package also contains a .LIB file that enables to integrate the DLL into user specific Fortran or C programs.
All property functions of the DLL are described in detail in the MANUAL.PDF that is part of the software.
The interactive program ThermoFluids
The interactive program ThermoFluids was developed for users, who need only occasionally to calculate or plot thermophysical properties. It is based on the program module FLUIDCAL.
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