Physchrometry formula for temperature above 200DegoC
Physchrometry formula for temperature above 200DegoC
(OP)
Hello,
I am trying to write a code to evaluate the mixing ratio, dew point temperature as a function of dry and wet bulb temperature.
There are lots of correlation out there and the ASHRAE standard gives some useful hints and formulae.
For the evaluation of water vapour pressure which is key to the computation of dew point, I have looked at using either Sonntag, Hyland and Wexler formulae, however, the accuracy above 200DegoC decrease rapidly and the error can be up to 15%.
SO, Has anybody done similar calculation for lower and higher temperature and would like to share some of his / her knowledge.
Much appreciated.
Francois
I am trying to write a code to evaluate the mixing ratio, dew point temperature as a function of dry and wet bulb temperature.
There are lots of correlation out there and the ASHRAE standard gives some useful hints and formulae.
For the evaluation of water vapour pressure which is key to the computation of dew point, I have looked at using either Sonntag, Hyland and Wexler formulae, however, the accuracy above 200DegoC decrease rapidly and the error can be up to 15%.
SO, Has anybody done similar calculation for lower and higher temperature and would like to share some of his / her knowledge.
Much appreciated.
Francois





RE: Physchrometry formula for temperature above 200DegoC
TTFN
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RE: Physchrometry formula for temperature above 200DegoC
David
RE: Physchrometry formula for temperature above 200DegoC
OK, Partially agree.
However with reference to Psychrometric Tables and Charts from Zimmerman and Lavine (Ed 1964), the table goes much further than 200oC.
For instance at 500oF (~277oC) with a mixing ratio of 0.6kg/kg the dew point would be about 84DegC (at Pressure 101253 Pa), and that is reading from Pyschrometric charts.
People usually know the 'Normal Psychrometric Chart' which usually goes to 35oC.
I understand that these table have been computed somehow, and that's what I am interested in.
Any idea where those are coming from ?
Francois
RE: Physchrometry formula for temperature above 200DegoC
Just because you can do the calculation, doesn't necessarily make it worth the expenditure of resources to do it.
TTFN
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RE: Physchrometry formula for temperature above 200DegoC
it is a real problem and easily solved if you have the equations of state. most chemical eng. hb cover it, as well as first year texts.
RE: Physchrometry formula for temperature above 200DegoC
Unfortunately haven't got many HB of chemical engineering.
found this link though: http:/
Looks interesting. They also seem to be using the Hyland and Wexler factor.
Their equations for estimating the dew point looks a bit difficult to digest. If you have any links or book ref I would be interested.
Thanks
Francois