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re: humidifiers/water fountains?
17 nov 2000
ken h. oils his way across the floor:
>nick@ufo.ee.vill.edu (nick pine) wrote:
>>.......maybe ken h or or karl can tell us how many boy scouts or
>>square feet of moving water are needed to keep a 70 f 1000 ft^2
>>room at 50% rh with 0.5 ach on a 50% rh 30 f day.
>boy scouts?
that was a joke. who wants little nazis around the house?
>square feet of moving water? who cares.
frugalarians do. we try to find interesting ways to do things cheaplier.
is a $50 smart fountain more interesting than a $500 hidden humidifier?
>if i want to my room at 50% rh, i adjust my humidistat to 50% and wait
>for the hygrometer to read 50%. why does it have to be complicated?
with maturity comes the desire for senility, and apparently fewer verbs.
now on to the question: 0.5 ach for a 1000 ft^2 room is 0.5x8000ft^3/h,
ie 67 cfm, but ashrae says 15 cfm per occupant is fine (or maybe less,
with lots of plants that make oxygen.) so let's caulk first, reducing
air leaks to 15 cfm (0.11 ach.)
now, our clausius-clapeyron approximation says 30 f air at 50% rh has
a water vapor pressure of 0.5exp(17.863-9621/(460+30)) = 0.085 "hg, ie
wo = 0.62198/(29.921/0.085-1) = 0.00177 pounds of water per pound of dry
air, and 50% 70 f air has 0.374 "hg with wi = 0.00788, and 13.4 ft^3 of
70 f air weighs about 1 pound, so ve must supply 24hx60mx15/13.4(wi-wo)
= 9.84 pounds (1.23 gallons) of water per day to maintain 50% rh.
evaporating this water takes 9.84x944 = 9,300 btu (2.7 kwh) of energy.
it would be very nice to seal the apartment tighter and heat incoming
fresh air by condensing the water from outgoing air... but hard to do.
andersen says the activities of a typical family of 4 supply 2 gallons
per day, so 1 person supplies 1/2 gallon, leaving 5.84 pounds per day,
which might come from a fountain or plants. plants are somewhat self-
regulating, supplying more water on dry days, but watering them is work.
has anyone tried the $59 #di1300 centralized-tank blumat watering system
from jade mountain at (800) 442-1972?
ashrae says a square foot of swimming pool loses about 0.1(pw-pa) pounds
of water per hour per square foot, so a square foot of 70 f water with
nearby 100% rh air would lose about 0.1(0.748-0.374) = 0.0374 lb/h or
24hx0.0374lb/h = 0.9 pounds of water per day, so we need about 6 ft^2 of
fountain (less because the water is moving) or 3 ft^2 of 2-sided plants
to keep the room at 50% rh.
herbach & rademan (800) 848-8001 http://www.herbach.com may still sell
fine navy surplus hair element humidistats in 1x2x5" solid brass boxes
full of holes, with a 20-80% range and 3-6% differential and an spdt
7.5 a 125 vac microswitch that can be wired to open or close on rising
humidity. their catalog number is tm89hvc5203, $4.95 each.
the humidistat might turn on h & r's tm89pmp5655 $3.75 3-6 vdc 600 ma
self-priming piston pump, which "will squirt a pulsating jet of water
15 to 20 feet with a capacity of 8 oz. in 1 minute. outlet 1/8" o.d. x 6"
long with restricted nozzle. with attached (easily removed) 4 1/2" length
of 1/8" o.d. flex tubing for inlet." we might make an orgasmatron above
a bowl in the living room or pump water from an automatically-refilled
toilet tank onto the back wall of a shower stall (wasting water, but
i've heard those toilet tank basin lids are no longer being made...)
nick
ps: if i say, "some women are stronger than some men," can ken find
a dozen websites that say "men are stronger than women"?... :-)
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