Humidification

[zesaint007]

Hello everybody,

I am working on very simple air humidification system (lab experiment):
mixing dry air (20 C) with air bubbled (at saturaion point) trough water (30 C).

I am a bit lost regarding the equilibrium i can achieve. In other words what equation could tell me the maximum humidity i can achieve...

Thank you very much for any answer

Greg

 

[Montemayor]

Greg:

I'm assuming you're an engineer - and a ChemE, specifically. If that's the case, you should have a solid background in psychrometry and, more specifically, simultaneous heat and mass transfer. By going to Google's search engine you can find the following site in less than a minute:

http://ohioline.osu.edu/aex-fact/0120.html

There, you'll find a refresher on how to resolve your problem. There is no equation for finding the maximum humidification of atmospheric air. The answer is graphically available in a psychrometric chart.

I think that should help you resolve the problem.

 

[zesaint007]

hello Montemayor and thank you for your answer,

Yes indeed i am very familiar with all the psychometric chart, but maybe my question wasnt clear enough or i am not understanding my problem...

In my saturation system (bubling air trough water) i would like to know more in details about achieving the equilibrum...maybe using Raoult or Dalton Law...

Thx for anything

 

[sshep]

007,

You are mixing dry air (20C) with humid air (100% humidity at 30C) and wish to know what is the maximum humidity you can achieve. The answer is 100% at 30C which is achieved as the flow of dry air approaches zero. Since this answer is totally obvious, you probably want something else and must give us more details.

Do you want to find the humidity for different ratios of wet and dry air? If so you can plot temperature and humidity vs 'wet to dry air ratio' by doing an enthalpy balance and water balance for each ratio you wish to plot- i.e. a simultanious mass and energy balance as was pointed out above. The humidity and temperature results for each wet-dry mix can then be obtained from your chart.

best wishes, sshep

 

[m777182]

There is nothing to add to sshep's answer; maybe a hint: for some experiments with humid air years ago we used a constant flow of dry air over a known area of water (25 C)surface. There was a formula I think in Perry how to get the rate of evaporation of water. So we used a conical vessel where the water surface area was very simply adjusted by water level and it worked well over a wide range of required humidities.
m777182

 

[zesaint007]

thank you very much everybody..i am going right away seek in the perry for this formula..i was afraid of doing some Dalton or Raoult simulation...but it seems much more easier than i thought.

have a nice week end

Greg