| nicksanspam@ece.villanova.edu 2007-06-19, 9:25 am |
| Art <begunaNOSPAMPLEASE@mindspring.com> wrote:
>There have been lots of posts about how crappy the Kenmore 70 pint
>dehumidifiers have turned out to be. Mine broke every year for
>the 3 years I kept it...
And they use lots of electrical energy. A Smart Vent (40 watts max)
would probably last longer. It has an electronic circuit that turns
on 2 small fans whenever the dew point of outdoor air is less than
the dew point of indoor air, ie the absolute humidity of the outdoor
air is lower. The Zomeworks H2 ventilator for battery boxes seems
to do the same thing, something like this, viewed in a fixed font:
outdoors up indoors
---------------
<-- moist air
----------------------
| --> dry air
| -------------------
| |
| | ---------------
| | heat exchanger
| |
| | down
| |
| | dip tube
as described in Steve Baer's ASES 2004 Humidity Chimneys paper. Moist air
is less dense than dry air, at the same temperature (hence the heat
exchanger.) Steve says a 1% moisture difference with a 2.5 foot height
difference (hence the dip tube) can make 75 feet per minute of air flow,
so a 6" pipe with an 8' height might make Pi(3/12)^2sqrt(8/2.5)75 = 26 cfm
flow and remove about 26x60x0.075x0.01x24h = 28 pints per day of water
from a basement, in dry weather, with a concentric pipe heat exchange
chimney inside the house, from the first floor ceiling to the basement.
The external "dip tube" might be a box with a transparent south side
and 150 Tyvek bags filled with desiccant clay, which can absorb 28%
of their weight in water, ie 53 pints:
http://www.uline.com/ProductDetail....S-1606&ref=1006
The Florida Solar Energy Center puts clay bags on wire racks in an attic
with a tin roof which heats up and dries them out during the day. After
they cool, at night, they remove moisture from house air that circulates
up through the attic. Here's some Desi-Pak (tm) tech info:
http://www.agmcontainer.com/desicca...performance.pdf
Graph 4 shows Desi-Paks can absorb 12% of their weight in 10 hours
at 30C and 60% RH, ie 2.3 pints per hour for the 189 pound collection
above. This rises with more airflow or thinner bags. Graph 3 says
they can absorb 8% in 100 hours at 25C and 10% RH, ie 0.15 pints
per hour for 189 pounds.
Nick
|