Determining parameters for trapped air in contact with water.

[Expi]

Hi everyone,

I need to evaluate parameters (heat capacity, density and thermal conductivity) for some very humid air.
I know the parameters for both dry air and water vapor. So I suppose the parameters I need will just be a linear combination of the other parameters, with a coefficient corresponding to the percentage of water in the air.
Problem is I do not know what is the proportion of water inside my air.

I have a 12cm wide layer of air in contact with plenty of water at a temperature of 39°C (312K) the contact area is about 5.46m². The air is trapped, I believe there are a few leaks keeping a balance in the air but that is not important for now.

Could someone validate my (basic) calculation, and overall could someone help me as to how figure out the humidity of the air.
I browsed a few tool boxes and did not find the parameters I need, if someone knows about that it would also be very welcomed.

Thank you for your times and your answers.
Have a good day.

 

[Expi]

Already found out that the density of water vapor is definately not calculated as I thought.

But like that :
rho = p1/(R1*T) + p2/(R2*T)
Where p are the pressions, R are some specific constants and T the temperature.

So I am wondering if I am not wrong for the other 2 parameters.