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<DIV>Bj, Tom,</DIV>
<DIV> </DIV>
<DIV>Can you speak about your unit we designed into the Bright'n Green project.
This thread needs your input please.</DIV>
<DIV> </DIV>
<DIV>Robert</DIV>
<DIV> </DIV>
<DIV>
<DIV>In a message dated 6/11/2012 4:20:26 P.M. Eastern Daylight Time,
nick@early.com writes:</DIV>
<BLOCKQUOTE
style="BORDER-LEFT: blue 2px solid; PADDING-LEFT: 5px; MARGIN-LEFT: 5px"><FONT
style="BACKGROUND-COLOR: transparent" color=#000000 size=2 face=Arial>Gennaro
Brooks-Church - Eco Brooklyn <info@ecobrooklyn.com> writes:<BR><BR>>
Has anyone experimented with the powder desiccants on rotation? Say have
<BR>> two trays and when one is in the house getting wet the other is
outside on <BR>> a south wall protected from the rain drying
out.<BR><BR>I've thought about using bentonite clumping cat litter in a raised
glazed <BR>tray in the sun with a concentric pipe air-air heat exchanger that
makes a <BR>wet airstream rising up from a house less dense than a dry
airstream falling <BR>down into a house, at the same temperature.<BR><BR>Jason
Holstine <jason@amicusgreen.com> wrote:<BR><BR>> The univ of maryland
solar decathlon house has done dessicants with water <BR>> wall features.
The maybe kind of might have info to share.<BR><BR>They are patent-crazy and
don't share information well, but they used <BR>calcium chloride, which is not
a very effective desiccant.<BR><BR>John Straube <jfstraube@uwaterloo.ca>
wrote:<BR><BR>> The reasons for the ratio of sensible to latent heat are in
the physics of <BR>> air, not government regs.<BR><BR>I've heard DOE rating
systems encourage this ratio.<BR><BR>> Get a psychrometric chart and draw
on the process in terms of enthalpy <BR>> (total energy).<BR><BR>Why bother
with drawings? Air at 40 F and 100% RH contains about 0.0053 <BR>pounds of
water per pound of dry air... 70 F air at 50% RH it contains about
<BR>0.0079. Cooling 1 cfm of 70 F air to 40 F takes about 30
Btu/h. Condensing <BR>the vapor takes about 1000x0.075(0.0079-0.0053) =
0.19 Btu/h. Rewarming the <BR>air to 70 F takes about 30 Btu/h. The latent
energy change is 0.19 Btu/h, <BR>and the net sensible energy used is 0 Btu/h,
for a 100% latent/sensible <BR>ratio.<BR><BR>> Drying to 40%RH requires me
to cool to just above 40F.<BR>> Now I need to reheat that air to get it to
70F, or I will overcool the <BR>> space. This is a normal one-speed
fixed output air conditioner.<BR><BR>Normal air conditioners cool air,
n'est-ce pas?<BR><BR>> You cant buy a small AC unit that puts arbitrary
amounts of heat back into <BR>> the air and the remainder to the
outside.<BR><BR>Why not? Basic physics or DOE ratings?<BR><BR>> If you
reduce airflow through the AC, the air gets colder, and this drags <BR>>
more moisture out the limit is 32F, at which point frost forms and quickly
<BR>> blocks it off.<BR><BR>So stop before the output air temp drops to 32
F...<BR><BR>> The easiest current answer is to get a really good efficient
variable <BR>> output AC unit, like a ductless split, run them slow (low
airflow, low <BR>> capacity) and then add back heat for the hours
needed.<BR><BR>Duct tape over some air outlets seems easier :-)<BR><BR>>
Enthalpy controlled ventilation is a common technique which reduces <BR>>
cooling needs exactly in the cool dry hours that are not a big problem.
<BR>> Often they only work when the outdoor temperature is below
60F...<BR><BR>Bad designs? Why don't they work at higher temps and lower
humidities?<BR><BR>> Surprisingly, the efficiencies of compression based AC
is now so high, <BR>> that economizers often use more energy to run the fan
through filters <BR>> ducts and dampers, than the AC uses when it is 60F
outside.<BR><BR>This efficient 2-watt filter with a low pressure loss:
<BR>http://www.nseproducts.com/electronicaircleaner.htm is for houses, not big
<BR>buildings with badly-designed HVAC systems. A 20"x20" version works well
<BR>with a $69 90 watt 2470 cfm Lasko 2155A window fan:
<BR>http://www.amazon.com/Lasko-Electrically-Reversible-Window-2155A/dp/B00002N5Z9/ref=sr_1_1?ie=UTF8&qid=1339445503&sr=8-1<BR><BR>Nick
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