Ind. Eng. Chem. Res. 2000, 39, 4439-4440
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“PE” Quickly Makes Available the Newest Equations of State via the Internet Oliver Pfohl,*,‡ Stanimir Petkov,† and Gerd Brunner† TU Hamburg-Harburg, AB Thermische Verfahrenstechnik, 21071 Hamburg, Germany
Sir: The calculation of phase equilibria plays an important role in industry and academia. The Windows program PE (Phase Equilibria) is an impressive and widespread software for the calculation of fluid-phase equilibria using equations of state (EOS). This paper briefly describes the authors’ reasons for offering a free download of PE from the Web. In general, the type of application, the knowledge of the users, and the money available for purchasing or developing the software lead to the use of different products that are optimum solutions under different boundary conditions: (i) Good commercial software, in general, is quite expensive and complex but does not offer all desired EOS. The complexity might prohibit simple ways for users to build in new EOS on their own. (ii) Self-made correlation tools are programs specially designed for certain problems and mostly written by Ph.D. students. Many of these programs can only be handled successfully with a lot of help from the programmer s especially in the absence of any adequate documentation. (iii) Developer tools are even more specialized selfmade programs that do an excellent job within the process of EOS development, but these tools are not necessarily helpful in other applications, such as use of the new EOS for the correlation of your own experimental data or comparison of calculation results with different EOS. The rapidly increasing number and complexity of EOS and the necessity to program each EOS individually before applying it hinder the test and the usage of new EOS. Statistical Associating Fluid Theory1,2 might serve as an example: SAFT is an excellent EOS for systems containing polymers or associating components. However, it would take a Ph.D. student who works on experiments and “just” wants to correlate his data a further 1-2 years to write some correlation software. On the other hand, the developers of new EOS are interested in others using their EOS, supplying feedback for further improvement, and writing papers about the beneficial capabilities of the new EOS. The World Wide Web offers completely new ways to improve the above-described situation. Some developers of new EOS already put their EOS on the Web s either a type of program for testing or a source code.3-5 This encourages engineers to try these new EOS. However, even if the source code is written in the engineer’s favorite programming language, quite a bit of programming work, compiling/linking, testing, and adjusting remains to be done. The program PE, for the calculation of fluid-phase equilibria, has been developed at TU Hamburg-Har† E-mail:
[email protected] and Petkov@ TU-Harburg.de. Fax: ++49/40/428784072. ‡ Bayer AG Leverkusen, ZT-TE 5.3, 51368 Leverkusen, Germany. E-mail:
[email protected]. Fax: ++49/ 214/3081554.
Figure 1. Main window of PE with menus and toolbar. PE offers two different modes for calculation and graphical output: pure component and mixture. The toolbar shows the selected EOS, mixing rule, and file that will be used for mixture calculations.
burg within the last 15 years and is one of the self-made correlation tools according to the above classification, having its origin in Ph.D. students’ calculations of highpressure equilibria with supercritical components. Within the last 3 years, PE became a typical Windows 95/98/ NT/2000 application6 using pull-down menus, dialog boxes, and a toolbar (Figure 1). PE already offers 40 different EOS as of now. Experimentally determined pure-component saturation properties, isotherms, and mixture phase equilibrium data are stored in ASCII files that can be generated using dialog boxes in PE. Based on these data, pure-component parameters for all EOS can be regressed using a standard dialog box (Figure 2). Similarly, binary interaction parameters for all EOS can be optimized in order to best reproduce binary or ternary phase equilibria. Based on these parameters, predictions of phase equilibria at other conditions can be made for systems with up to 10 components. Recent work on the correlation and evaluation of pure-component EOS parameters7,8 and work on multicomponent, multiphase calculations8,9 provide proof that PE generates many different types of diagrams. These diagrams include comparisons of experimental and calculated data in a quality that is suitable for publication. The program PE, together with a 150-page manual,10 online help, and examples, can be downloaded for free from http://vt2pc8.vt2.tu-harburg.de. Meanwhile, about 50 different thermodynamic groups use PE. There is consistent positive feedback. PE allows the users to include new EOS “on-site” easily simply by writing subroutines for the calculation of P(T,F,x) and φi(T,F,x) but permitting the usage of the PE Windows interface as well as the usage of all subroutines such as flash, graphical output, and parameter fitting. The additional possibility of supplying subroutines with new EOS to the PE project on the Web has been added after developers’ requests underlining the above-mentioned will of the developers to add their own EOS. Perturbed-chain SAFT5 had already been
10.1021/ie000778t CCC: $19.00 © 2000 American Chemical Society Published on Web 10/14/2000
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Ind. Eng. Chem. Res., Vol. 39, No. 11, 2000
results with the results of other EOS without the timeconsuming necessity of programming anything themselves. Further, this is believed to improve the development of new EOS, because the developers will have many more users applying their EOS, immediately leading to enhanced feedback and honor in the case of successful applicability. Literature Cited
Figure 2. Standard dialog box for pure-component parameter optimization using different EOS. The start values for the regression are retrieved from a data bank and can be changed manually. Selecting the check boxes will lead to the optimization of the checked parameters; the other parameters will be held constant during the optimization. Different types of association sites (SAFT and CPA-EOS) can be selected using the combo boxes.
implemented by F. Tumakaka, TU Berlin, before the EOS papers have been published. This feature is believed to enable and encourage engineers to correlate their data with the most modern EOS and compare the
(1) Chapman, W. G.; Gubbins, K. E.; Joslin, C. G.; Gray, C. G. Theory and Simulation of Associate Liquid Mixtures. Fluid Phase Equilib. 1986, 29, 337. (2) Huang, S. H.; Radosz, M. Equation of State for Small, Large, Polydisperse, and Associating Molecules. Ind. Eng. Chem. Res. 1991, 30, 1994. (3) Deiters, U. K. http://www.uni-koeln.de/math-nat-fak/ phchem/deiters/. (4) Fischer, J. http://www.boku.ac.at/iluet/tt/tt.htm. (5) Gross, J.; Sadowski, G.; Arlt, W. http:// pcitr4.fb10.tu-berlin.de/pc-saft/pc-saft-home.html. (6) Petkov, S.; Pfohl, O.; Brunner, G. PE: a Scientific Computer Program for the Calculation of Fluid-Phase Equilibria. International Workshop on Scientific Computing in Chemical Engineering II, Hamburg, May 26-28, 1999. Published in: Scientific computing in chemical engineering; Keil et al., Eds.; Springer: Berlin, 1999; p 279, ISBN 3-540-65848-3. (7) Pfohl, O.; Giese, T.; Dohrn, R.; Brunner, G. Comparison of 12 Equations of State with Respect to Gas-Extraction Processes: Reproduction of Pure-Component Properties When Enforcing the Correct Critical Temperature and Pressure. Ind. Eng. Chem. Res. 1998, 37, 2957. (8) Pfohl, O.; Brunner, G. Use of BACK To Modify SAFT in Order To Enable Density and Phase Equilibrium Calculations Connected to Gas-Extraction Processes. Ind. Eng. Chem. Res. 1998, 37, 2966. (9) Pfohl, O.; Pagel, A.; Brunner, G. Phase Equilibria in Systems Containing o-Cresol, p-Cresol, Carbon Dioxide, and Ethanol at 323.15-473.15 K and 10-35 MPa. Fluid Phase Equilib. 1999, 157, 53. (10) Pfohl, O.; Petkov, S.; Brunner, G. PE 2000: A Powerful Tool to Correlate Phase Equilibria; Herbert Utz: Munich, 2000; ISBN 3-89675-751-2.
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