Evaporation efectiveness at colder climates

[stern]

Hi there,

I was reading some theory of evaporative cooling equipment and learned that water requires sensible heat from air to evaporate (heat converted to latent heat).

My questions are, for a cold weather with low RH like for instance 17.6 F db, 51% RH is it still possible for water to evaporate ? Water temperature impacts this answer?

How could I find how much sensible heat is required in air to evaporate x amount of water in the air?

Thank you !!

 

[dvd]

sublimation

get the thermodynamic tables for water in frozen state and compare to water vapor at same conditions.

 

[IRstuff]

The issue is going to be the saturation limit of the air, which is dependent on the temperature. Since the colder air cannot support a higher absolute humidity, evaporative cooling will be diminished

TTFN
faq731-376

 

[zdas04]

There are two things you have to keep in mind: (1) the atmosphere is a really big heat sink (i.e., your 17.6F is actually 477R, a lot of room to absolute zero); and (2) cold air typically has very low relative humidity.

Amoco did a study in the late 90's that was widely published that showed freeze/thaw evaporation to be very effective.

A company called Snow Machines, Inc. (oddly enough they sell snow making equipment) noticed long ago that the amount of water recovered below a hill of man-made snow was a small fraction of the amount of water they started with. This observation led them to market a line of equipment that is specifically designed to accelerate evaporation.

In both cases, you have to access the liquid water under the frozen surface and take steps to keep it from freezing in your spray equipment. Neither condition is insurmountable, but it requires some engineering.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[stern]

Thank you all!