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[odc5.3]

Hello, 

This is more of a hypothetical question to enhance my own understanding of the subject. 

 

Lets we have air with relative humidity X% at a given temperature. 

 

P = total pressure

p = partial pressure

ps = saturation pressure 

 

From Dalton's law we have: P1 = p(air) + p(water vapour). 

 

Now the air is compressed to P2 =  2*P1. 

 

from Dalton law's  we have: P2 = 2*p(air) + 2*p(water vapour) 

 

What happens if: 2*p(water vapour) > ps(water)? 

 

Does Dalton's law not apply in this case? Because from under standing, at P2, 

the p(water vapour) would be fixed at ps(water), and would would start condensing out of the air. 

 

If anyone could clarify this it would be much appreciated. 

 

[marchem]

you may assume that water saturation pressure depends from temperature only,

Dalton's law says that if you increase the system pressure a volume unit will contain more vapor before to start condensation,

however when you compress a fluid, temperature also increases which means higher water saturation pressure (and possibly all water in vapor phase).