Water condensation question:Volume of water extracted from Air in fonction of diverse parameters

[Ludo]

Hello everyone,

 

Is there is a formula that would allow me to calculate the volume of water that can be extracted from air in fonction of the area of the collecting surface, the airflow, the air relative humidity rate and the difference of temperature between collecting surface and ambient air.

basically I need the formulas to answer a question of this type :

 

if I was to send 10 liters of air (at 30 celsius degrees / 65% relative humidity), every second, on a 1 sq meter surface cooled at 10 degrees celsius,and providing I manage to collect all the extracted water, how much water would I collect in, say, one hour?

Thanks in advance for your answer

Ludovic

[Enthalpy]

Hi Ludovic, welcome here! (Priko?)

 

The maximum amount of water that can be extracted is easy. The efficiency of the collector is difficult to predict, but you can try to make it good.

 

Water has a vapour pressure that depends on the temperature [...of the water, but let's forget that]. Below 100°C this pressure is well under 1 atm (that's why water doesn't boil) but it contributes to the composition of the atmosphere as a partial pressure. Compare it with 1 atm, you have the maximum proportion of vapour (in volume) that air can contain. Multiply by the relative humidity, you have the volume proportion of vapour.

 

When you don't forget that water weighs 18g per mole and air around 29g, you even get a mass of contained vapour per air volume.

 

Then the collector shall cool all the contained vapour to be efficient which means more or less all the air, and here nice physics becomes nasty technology.

 

But if you cool all the air to 10°C an leave no liquid water in the outgoing air, then you leave only the vapour corresponding to the partial pressure at 10°C. The difference gives the (ideal maximum) collected water.

 

http://www.engineeringtoolbox.com/water-vapor-saturation-pressure-air-d_689.html

 

Marc