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Evaporation of water in an algae raceway pond?

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Posted by Curbie on December 7, 2009, 9:50 pm

I'm trying to calculate the evaporation rate of an algae raceway pond
using the formula (which seems applicable) given here:

Does anyone know how to calculate the values for Pdw and Pw???

PDP = saturation pressure at room air dewpoint, in.Hg.
PW = saturation vapor pressure taken at the surface water temperature,



Posted by Jim Wilkins on December 7, 2009, 11:27 pm


Posted by Curbie on December 8, 2009, 2:45 am

On Mon, 7 Dec 2009 15:27:19 -0800 (PST), Jim Wilkins

Thanks Jim,

I put that table into a spread-sheet with a column to covert mb to
inHg so I think I can start testing that evaporation equation.


Posted by Jim Wilkins on December 8, 2009, 12:46 pm

A surface film of oil will retard evaporation considerably.

You can measure the evaporation rate with a pizza pan of water on a
weighing scale. A piece of yarn hung over it will show air flow. I
think the rate vs velocity curve straightens out around walking speed,
it's similar to wind chill.

Radio Shack sells temperature and humidity displays with remote
sensors, the older model I have is quite good on temperature and
within about 10% on humidity, The sensors can be checked and compared
in a steamy shower room at 100% humidity.


Posted by Curbie on December 8, 2009, 2:55 pm

On Tue, 8 Dec 2009 04:46:40 -0800 (PST), Jim Wilkins


An interesting idea, I be a bit concerned that the oil may impede the
algae's ability to get at atmospheric CO2, but easily tested and worth
a try.

Another easy test, I'd like to get the math to work, but good
verification and backup if I can't.

Does Radio Shack's device have data logging capabilities?



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