Frequently asked questions
Q: What is VLE - Calc ?
A: The name is from the words vapor-liquid equilibrium Calculator. Essentially it is an on-line service for prediction of vapor-liquid and liquid-liquid phase equilibrium data of pure compounds and mixtures, moreover calculation of distillation and extraction.
Q: Is this program free of charge?
A: Yes, the use of VLE - Calc is completely free of charge.
Q: But there are such programs and databases on the Net already. What is special on this?
A: VLE - Calc differs from other similar programs that
- it is really free
- permits these calculations in any mixture-combinations of organic compounds
- in such a way that you do not need to bother about the non-ideality (parameters).
- And finally: a unit converter lets the diagrams and calculation results to be converted easily to several measure units.
Q: How does the program take into account the non-ideality of liquid mixtures?
A: By the use of UNIQUAC / UNIFAC activity coefficient models. UNIQUAC is used when all of the model parameters of all compound-pairs of the selected mixture are available in the database. Otherwise the UNIFAC model is used, which may be slightly less accurate, but it does not need these specific parameters. The specific UNIQUAC parameters of exact compound-pairs are stored in the database only in the following circumstances: 1.: phase equilibria reference data set (measurements) of the required variety and quality are available, and 2.: the application of the UNIFAC model on these reference data seems to be too inaccurate. A typical example is the case of THF-water.
Q: What about the reliability of the diagrams/calculation results?
A: The precision of the results are generally useful for less demanding industrial calculations and educational/demonstrational use. Not recommended for precise calculations and for research.
Q: Is the program capable to predict system equilibria with three coexisting liquid phases?
A: Not yet, but it is planned.
Q: What if crossing tie-lines appear on the LLE diagram of a ternary system?
A: Yes, unfortunately it may happen, because the LLE (flash) algorithm is not perfect yet. In this case those tie lines are relevant, most of which to each other consistently line up. Please do not take into account the outhanging/crossing lines.
Q: Found an error/mistake.
A: However during building the database and the program reliability was the point, errors can still occur. This service is under continuous development and sorry for any incidental error, but I can not take any responsibility for any damages or losses originating from them. Use the program at your own risk! Corrections are welcome at firstname.lastname@example.org.
Q: How can I download the program?
A: Sorry, no downloadable version here. This is only an on-line application.
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