4 replies to this topic

[engprocess]

Hello ,
I look for a chart or any thing else to read or convert an amount of water in PPMv to the equivalent dew point temperature.
thanks
ex: I have 1 pmmv water in gas , what is the dew point .
thanks.

[aluma]

EngProcess,

First of all, you need to know the total pressure of the gas. Knowing the mole fraction of water in the system(=vol fraction), you can obtain the partial pressure of water. According to Raoult's law,

Partial pressure= vapour pressure of water*activity coefficient

For simplicity, you can assume activity coefficient of 1. Thus you obtain your vapour pressure. From here it is as simple as checking a saturated steam table for the temperature that corresponds to this pressure(vapour). That's your dew point!

[vinay]

Please also refer following recent posting on cheresources.com related to Dew point

http://www.cheresour...?showtopic=5961

regards,
vinay

[hygrometry]

You can download a freeware calculator from www.phymetrix.com that will perform all of these conversions.

Hope this helps!

[DRS]

Hi Hygrometry,

Thanks for the excellent tip. That is a pretty good calculator.