Calculation of boiling point at arbitrary pressure
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Everyone: Does anyone know how to calculate the boiling point of a liquid at a certain pressure, given its standard boiling point?
There’s no need to calculate; the results may not be accurate. Property manuals can be found. It’s in the forum! Go and look for it yourself!
It can be calculated using Antoine’s equation, which is the relationship between pressure and temperature
For some common liquids, approximate values can perhaps be calculated using equations, but this is inaccurate for many liquids; it’s better to consult relevant manuals
For a certain amount of gas under specific conditions, the relationship between temperature and pressure is given by pv=nrt (Clausius equation). The volume flow rate V equals the inner diameter of the pipe multiplied by the flow velocity; flow rate is equal to volume divided by time
According to the Dulong rule, when the pressure is not high, one can first use a steam table to find the pressure corresponding to the liquid’s standard boiling point, and then determine the boiling point of water at that pressure; the difference between these two boiling points is assumed to be x. Next, the boiling point of water at the non-standard pressure is determined, and the boiling point of the liquid at that non-standard pressure is then equal to the boiling point of water at that pressure plus x. This method is suitable for estimation when data is unavailable, provided that the pressure is not too high (with normal pressure as a reference); otherwise, the error will be significant
Actually, using Pro2 for calculations is the most convenient. Enter the material composition, set the pressure to the desired value, select the boiling point for temperature, and the calculation results will be available immediately
It is understood that there is currently no relatively accurate calculation formula available. Even if there are formulas, they are merely empirical formulas. If empirical formulas are used for calculation, it involves certain parameters in those formulas, the values of which are also empirical data (derived by scientists through numerous experiments; depending on the perspective or conditions, as well as the scientist, these values often vary). To find relevant data, it is recommended to consult the manual as it is faster and more convenient. I recommend one book: *Handbook of Physical Properties of Chemicals and Chemical Engineering Materials* (published by the Chemical Industry Press).
In less precise situations, it is quite convenient to use formulas for calculations; looking up data can be troublesome. Of course, for more accurate calculations, one has to consult a manual.