Rational approximations to fluid properties

Technical Report · Tue May 01 00:00:00 EDT 1990

DOI:https://doi.org/10.2172/7121381· OSTI ID:7121381

Kincaid, J M

The purpose of this report is to summarize some results that were presented at the Spring AIChE meeting in Orlando, Florida (20 March 1990). We report on recent attempts to develop a systematic method, based on the technique of rational approximation, for creating mathematical models of real-fluid equations of state and related properties. Equation-of-state models for real fluids are usually created by selecting a function {tilde p} (T,{rho}) that contains a set of parameters {l brace}{gamma}{sub i}{r brace}; the {l brace}{gamma}{sub i}{r brace} is chosen such that {tilde p}(T,{rho}) provides a good fit to the experimental data. (Here p is the pressure, T the temperature and {rho} is the density). In most cases a nonlinear least-squares numerical method is used to determine {l brace}{gamma}{sub i}{r brace}. There are several drawbacks to this method: one has essentially to guess what {tilde p}(T,{rho}) should be; the critical region is seldom fit very well and nonlinear numerical methods are time consuming and sometimes not very stable. The rational approximation approach we describe may eliminate all of these drawbacks. In particular it lets the data choose the function {tilde p}(T,{rho}) and its numerical implementation involves only linear algorithms. 27 refs., 5 figs.

• Research Organization: State Univ. of New York, Stony Brook, NY (USA). Dept. of Mechanical Engineering
• Sponsoring Organization: DOE/ER
• DOE Contract Number: FG02-87ER13648
• OSTI ID: 7121381
• Report Number(s): DOE/ER/13648-12; ON: DE90012531
• Country of Publication: United States
• Language: English

Related Subjects

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PHYSICAL AND ANALYTICAL CHEMISTRY
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FLUIDS
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PHASE TRANSFORMATIONS
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