psychrometrics question

[PEinOHIO]

so hvac is not my area, something i was thinking about:

so if water is under 212 F (boiling point) it is considered a subcooled liquid. however, that water can still evaporate into the air when its a subcooled liquid. does it evaporate only when its temp is above the dew point temp? i guess my main question is what is the difference between boiling and evaporation?

also, is evaporation pressure dependent?

 

[IRstuff]

also, is evaporation pressure dependent?

Yes, the same is true of boiling point, so boiling is easier to do in Denver, and at a lower temperature. You may wish to read:

http://en.wikipedia.org/wiki/Boiling

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[MintJulep]

Evaporation is driven by the difference in vapor pressure of the liquid water and the water in the air.

 

[DRWeig]

Definition of relative humidity is the ratio of water vapor pressure to what the water vapor pressure would be at saturation with the same temperature and pressure conditions. Varies with moisture content, pressure, and temperature. For more depth, check the wiki at

http://en.wikipedia.org/wiki/Relative_humidity.

So as long as the air is not saturated (100 percent relative humidity), water will continue to evaporate. You can saturate the air, this stopping evaporation, by increasing pressure, or by reducing temperature, or by simply allowing evaporation to continue (adding water vapor).

Good on y'all,

Goober Dave

 

[ChrisConley]

You can (as a reasonable analogy) view the evaporation of water into air as water being 'dissolved' into the air. This is different from the phase change process of boiling.

 

[willard3]

Vapor pressure is the driving force.....higher vapor pressure to lower vapor pressure.

Some psych charts have vapor pressure and the physics is simple if you look at the other stuff on the chart.