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Contents of /trunk/models/johnpye/fprops/README.txt

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Wed Oct 8 23:05:53 2008 UTC (13 years, 8 months ago) by jpye
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2 ======
4 Code in this directory is a standalone pure fluid property evaluation library
5 primarily based on the Helmholtz free energy formulation used by various
6 authors for high-accuracy thermodynamic property correlations.
8 This is currently experimental software, with many bugs. You should carefully
9 test the results from this library before you rely on any of its values.
11 Integration is provided to allow these routines to be called from ASCEND, but
12 the support is still partial, and still lacks the derivative expressions that
13 allow the most efficient possible convergence during iteration.
14 ________________________________________________
15 | |
16 | More details are available on the ASCEND Wiki: |
17 | http://ascendwiki.cheme.cmu.edu/FPROPS |
18 |________________________________________________|
20 Ideal gas properties
21 --------------------
23 Helmholtz property correlations are given in terms of the 'ideal' part and the
24 'residual' part. The ideal part is based on the zero-pressure limit, where
25 the specific heat capacity of a fluid approaches that of an ideal gas, and
26 consequently is a function of temperature only, cp0(T).
28 We provide a means for specifying cp0(T) as a sum of power terms and
29 'exponential terms'; see the Span paper (nitrogen.c) for some discussion of
30 this.
32 The ideal part of the Helmholtz free energy is calculated by integrating
33 the cp0(T) function as described in Tillner-Roth (see ammonia.c).
35 In some cases, authors give their results for the Helmholtz free energy
36 without providing their original correlation for cp0(T). In this case
37 we back-calculate what the temps in the cp0(T) correlation must be, and check
38 that the form of the resulting re-integrated phi0 expression is correct.
40 Supported fluids
41 ----------------
43 Each fluid that is supported by this library must currently have .c and .h
44 file in which the correlation parameters are provided, and optionally including
45 a test suite to validate the results.
47 We propose to add support for a text-based input file format, and possibly a
48 database for simple fluid correlations of the type currently provided by ASCEND,
49 Sim42, and other process simulators. But that is a job for later.
51 --
52 John Pye
53 09 Oct 2008.

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