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desicant AC

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Posted by Jeff on March 10, 2007, 11:14 pm
 
   With summer a few month away, I'm thinking about AC. I hope to have
my solar hot water collectors running by then. (The air collector is
running still in test mode).

   So it seem to me that a liquid desicant (calcium chloride probably)
would be the way to go for the dehumidification. Air could be run
through a "swamp cooler", either before, after, or both.

Calcium Chloride dessicant dehumidifier diagram:

<URL:
http://www.samedanltd.com/members/archives/PMPS/Winter2001/KoenEgberts.htm  
/>

AC example:

<URL:
http://www.energy.ca.gov/2005publications/CEC-500-2005-083/CEC-500-2005-083.PDF  
/>

   Anyone know about these? Or have the enthalpy charts for various
concentrations of calcium chloride in water? Or the enthalpy of air at
different humidity levels and temperatures?

   Thermodynamics is soooo hard. For me, at least!

On a differnt note, is the max possible (generator) efficiency dependant
on just temerature, or is it enthalpy change?

   Jeff

Posted by Jeff on March 16, 2007, 4:06 pm
 
Jeff wrote:

   It looks lke I'm the only one in this group thinking about this!

   I've found a few psychrometric charts. I think the best one is here:

<URL:
http://www.coolerado.com/CoolTools/Psychrmtrcs/0000Psych11x17US_SI.pdf  />


   The way I see this is a salt spray lowers humidity to about 40%, a
swamp cooler lower the temp about 17 F  and then a follow up salt spray
lowers the humidity again to 40%.

   Dehumidification can be done by either sprays or passing air through
a "grate" of vertical baffles that calcium chloride wicks down. Same
method can be used to regenerate the solution.

   More later...

   The "cool" thing is that unused solar heat can be used in the summer,
and that usefull work can be store as latent heat in a salt solution.

   Jeff


http://www.energy.ca.gov/2005publications/CEC-500-2005-083/CEC-500-2005-083.PDF  


Posted by Morris Dovey on March 16, 2007, 11:24 pm
 Jeff wrote:

| It looks lke I'm the only one in this group thinking about this!

Not really. I'm looking using solar heat to drive a fluidyne (liquid
piston Stirling) to produce mechanical energy - then using that
mechanical energy to drive another Stirling to end up with cold/hot
sides.

When working, that lash-up should provide solar-powered air
conditioning and refrigeration.

Still working on getting the first stage to percolate reasonably well,
and can report a bit of success this past week. My compadre in the
project has promised to drop off some video files he shot of one of
the most recent test engines running last night.

I'll put 'em on my web site at the link below as soon as I can.

We're still a fair ways short of solar air-conditioning, but we're
moving with all the speed our resources allow...

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/StirlingProject.html



Posted by Jeff on March 17, 2007, 3:20 am
 Morris Dovey wrote:

   Hi Morris,

   I looked over the fluidyne link below. The parabolic collector looks
very interesting. Seems to me that with 700F heat you might have some
pretty good carnot theoretical efficiency, approaching 60%. If you got
half that, it would be pretty good.

   Have you considered other working fluids than water? Something that
would operate at that temperature?

   Jeff


Posted by Morris Dovey on March 17, 2007, 5:26 am
 Jeff wrote:
| Morris Dovey wrote:
|| Jeff wrote:
||
||| It looks lke I'm the only one in this group thinking about this!
||
|| Not really. I'm looking using solar heat to drive a fluidyne
|| (liquid piston Stirling) to produce mechanical energy - then using
|| that mechanical energy to drive another Stirling to end up with
|| cold/hot sides.
|
|    I looked over the fluidyne link below. The parabolic collector
| looks very interesting. Seems to me that with 700F heat you might
| have some pretty good carnot theoretical efficiency, approaching
| 60%. If you got half that, it would be pretty good.
|
|    Have you considered other working fluids than water? Something
| that would operate at that temperature?

I /have/ done a bit of head scratching - but so far the focus has been
on arriving at a grasp of the design rules and working our way up to a
practical 1 to 2 hp engine. The first application (pump) begs for an
inexpensive PVC plumbing solution so, unless we can puzzle out how to
inexpensively move the heat through a PVC wall without melting it, we
won't be using a concentrating collector.

The solar refrigeration apparatus will most likely be a metal
construct and should be suitable for high-temperature input, but we've
agreed to limit ourselves to solving one problem at a time. It'd be
all too easy to become distracted with new possibilities - with the
result that nothing at all would be completed. Still, the interest is
there and any suggestions you might have will be much appreciated...

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/solar.html



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