Water vapor transmission rate
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nick pine
Jun 29, 2011, 7:48:45 AM6/29/11
to sunspace, mell...@ursinus.edu
> Plastic film containers lose water vapor over time. A continuous duct might be easier to top up than 48 plastic film drum liners... http://www.devicelink.com/mpb/archive/98/09/005.html says 100 square inches of low-density polyethylene loses about 0.4 grams of water per day per mil (0.001") of thickness at 40 C (104 F), with 0% RH on one side and 35% on the other. A graph shows how this decreases linearly with inverse absolute (1000/T(K)) temperature.
>
> With 2x12x4x8x144 = 110,592 in^2 of surface, the 12 shelves might lose about 0.4x110,592/100/6 = 74 grams (2.6 oz) of water per day or 59 pounds (about 7 gallons) of water per year.
>
> Adding salt to the water until the vapor pressure of the hot saltwater and the surrounding air are equal might help...
Looks like sodium chloride won't do it. Maybe calcium or lithium...
http://www.mrc-eng.com/Downloads/Aqueous%20LiCl&CaCl2%20Solution%20Props.pdf
Nick
>
> With 2x12x4x8x144 = 110,592 in^2 of surface, the 12 shelves might lose about 0.4x110,592/100/6 = 74 grams (2.6 oz) of water per day or 59 pounds (about 7 gallons) of water per year.
>
> Adding salt to the water until the vapor pressure of the hot saltwater and the surrounding air are equal might help...
Looks like sodium chloride won't do it. Maybe calcium or lithium...
http://www.mrc-eng.com/Downloads/Aqueous%20LiCl&CaCl2%20Solution%20Props.pdf
Nick
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