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Solar pump and air-conditioning update - Page 2

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Posted by Morris Dovey on July 14, 2007, 2:25 pm
 
Jeff wrote:

| What kind of a head? Seems to me you should be able to get some
| efficiency figures with the flow rate and the head, anything over a
| few percent would be outstanding. The carnot maximum isn't very
| high.

Excellent question. We've already had this conversation once, Jeff,
and you surely recall how it went. :-)

This time I can answer that, for the moment, I don't really care about
efficiency. I only care about getting a minimal-cost easy-to-build
fluidyne larger than toy size to work well enough to satisfy my own
notion of "good enough".

Engineering types, and engineers-in-training, are invited to build
more efficient, less expensive, longer-lasting versions. If they'd
done so before now, millions of people would've been better off today.

I don't understand why the problem had to wait for someone totally
unqualified to provide a solution. It's hard to believe that so many
qualified engineers couldn't bring themselves do what so obviously
needed doing. :-/

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



Posted by sno on July 14, 2007, 8:38 pm
 


Morris Dovey wrote:

Just wondering if you have any idea of what the minimum temperature
difference this pump will work at....as you have it at the present
time....am wondering if it would work with a flat plate solar
collector...

thanks for any info...have fun....sno

  No matter how dangerous nuclear power may or
  may not be.....
  Is it any more dangerous then what we are doing
  now.....???
  
  This tag line is generated by:
    SLNG (Silly Little Nuclear Generator)

Posted by Morris Dovey on July 14, 2007, 10:11 pm
 sno wrote:

| Just wondering if you have any idea of what the minimum temperature
| difference this pump will work at....as you have it at the present
| time....am wondering if it would work with a flat plate solar
| collector...

I don't know yet. So far, we've only driven this one with a heat gun.
The air goes into the hot side exchanger at about 650F and comes out
about 300F, and we're not boiling any of the water. We don't have any
way to control the input temperature, so I can't really answer your
question about minimum temperature.

Just so that you'll know that I'm not dodging your question - this is
a brand new (completed on Wednesday) construction and (for us at
least) a brand new design without the benefit of any engineering
calculations. It's the starting point for what'll probably be a long
series of "cut and try" iterations. It'd have been nice to take a
"cookbook" approach, but we weren't able to find a recipe and the gas
laws we studied back in high school don't include any time
dependencies - an absolutely essential ingredient for an engine.

We don't have any instrumentation beyond eyeballs, wristwatches, and a
(slow) thermometer for collecting operating data. Anyone wanting data
requiring better instrumentation is invited to bring or send it to us.
If you'd like information about things like minimum operating
temperature, you're invited to send equipment that will produce at
least the range of temperatures in which you might have an interest.

Meanwhile (not holding our breath waiting for any of that) we'll keep
on doing our best to make it run as well as it can within the
limitations we have.

I can't think of any good reason why a fluidyne of this configuration
couldn't run at temperature differentials achievable with flat plate
collectors. I have a panel in the shop that'll eventually be used in
testing when we're ready to move on to solar heat.

| thanks for any info...have fun....sno

You're welcome. Well, it's fun when things work - but there have been
times when there was strong temptation to toss the whole works in the
trash bin.

Usually when things work, I add a photo or drawing to the web page.
It's fun to think that someone (somewhere) might see the page and have
an "Aha!" experience.

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



Posted by Jeff on July 16, 2007, 2:17 pm
 Morris Dovey wrote:

Well, there's lots of things I don't remember, but I get the gist!


Seems to me that a natural use for this would be irrigation, another
would be circulating heated water for solar apps. Either way the pump
must overcome some head, a pump that pumps large amount of water at 0
head has little practical use.

Maximizing for flow rate at a very small head is probably not what you
want. You may very well find that a pump that works less well at O head
works much better at a higher head. This is very common for commercial
pumps.  Seems that different types of pumps have different flow rate
versus pump head curves.

   So, forget efficiency, but think of loading down the pump to get some
idea of what it will do in real life.

   Good luck with your project!
   Jeff




Posted by Morris Dovey on July 16, 2007, 2:52 pm
 Jeff wrote:
| Morris Dovey wrote:
|| Jeff wrote:
||
||| What kind of a head? Seems to me you should be able to get some
||| efficiency figures with the flow rate and the head, anything over
||| a few percent would be outstanding. The carnot maximum isn't very
||| high.
||
|| Excellent question. We've already had this conversation once, Jeff,
|| and you surely recall how it went. :-)
|
| Well, there's lots of things I don't remember, but I get the gist!

I'm the guy who doesn't like to publish performance numbers that can't
be guaranteed. I still haven't managed to add a "standard sun" to our
meager collection of test equipment. You were right that it does put
some people off, but word of mouth from solar panel customers has been
better than just "ok". I'm pretty sure I won't be able to do that with
the pump, but there's a lot of testing (and improving) to be done
before I dare do any bragging.

|| This time I can answer that, for the moment, I don't really care
|| about efficiency. I only care about getting a minimal-cost
|| easy-to-build fluidyne larger than toy size to work well enough to
|| satisfy my own notion of "good enough".
|
| Seems to me that a natural use for this would be irrigation, another
| would be circulating heated water for solar apps. Either way the
| pump must overcome some head, a pump that pumps large amount of
| water at 0 head has little practical use.

Yes! I'm aiming at irrigation, remote village water supply, and
flood/disaster recovery operations. The circulating pump application
is planned, and we think that this contraption may work well for
pumping hot air (for such mundane tasks as warming the water in
livestock watering troughs to prevent winter freeze).

| Maximizing for flow rate at a very small head is probably not what
| you want. You may very well find that a pump that works less well
| at O head works much better at a higher head. This is very common
| for commercial pumps.  Seems that different types of pumps have
| different flow rate versus pump head curves.
|
|    So, forget efficiency, but think of loading down the pump to get
| some idea of what it will do in real life.

We've already discovered that it does appear to work better under load
and we're itching to see if it'll pump water up from 100-200' - and
how large a well pipe we can lift through. With our limited experience
with PVC pipe I suspect that before we're done we'll have both
implosions and explosions, and we're certain to have at least a few
melt-downs. :-)

| Good luck with your project!

Thanks! We have a lot to learn, but (finally) haveing an operating
engine will speed that process...

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



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