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Risers Vs Absorber Plate

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Posted by Brian Graham on August 26, 2004, 2:56 pm
 
I seem to be seeing two general concepts in solar water heaters.

The first would be a copper bonded to an absorber plate. The second would be
with small risers (3/8" perhaps between a header & footer which are much larger
- 3/4" perhaps) with thin fins attached. Either approach would be in an
insulated box, behind glass of course.

My impression is that the second concept - risers with fins - is more effective
than a more simple copper run (coiled or snaked) bonded (solder/brazed) to a
plate.

My question would be how much more effective is the header/riser approach, and
why?
—
Brian

Posted by Duane C. Johnson on August 26, 2004, 9:37 pm
 
Hi Brian;



The thing that trumps this method is the ability to
effectively drain the system.


For similar water volume rates they should be fairly
similar in performance.

However, the power needed to move this water in the
serpentine model is significantly higher.

Duane


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Posted by Brian Graham on August 27, 2004, 4:50 pm
  

Actually, a serpentine placed sideways is simple to drain. A coil, on the other
hand..


That's the real question - How similar?  If the fins bring the temp to 180 and
plate only to 160, that's quite good enough. I suppose even 120 is fine - that's
what HWT's are usually set to anyway. The other question, naturally, is how big
a unit is required to obtain that. That said, the temp will rise until an
absorbtion limit is reached, or water flow removes it. So flow speed, tank size,
insulation etc will all affect the temp in the collector.


That I can understand.  And if I'm going to wrap my wood stove with copper runs
too...
:-)

—
Brian

Posted by Brian Graham on August 31, 2004, 5:29 pm
 Not seeing any other feedback, I'm presuming that it doesn't much matter whether
you say po-tay-to or po-ta-to.. Ie, the 2 approaches are fairly close in
efficiency and you can expect good hot water from either...

??

—
Brian

I seem to be seeing two general concepts in solar water heaters.

The first would be a copper bonded to an absorber plate. The second would be
with small risers (3/8" perhaps between a header & footer which are much larger
- 3/4" perhaps) with thin fins attached. Either approach would be in an
insulated box, behind glass of course.

My impression is that the second concept - risers with fins - is more effective
than a more simple copper run (coiled or snaked) bonded (solder/brazed) to a
plate.

My question would be how much more effective is the header/riser approach, and
why?
—
Brian



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