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Baffle and plate spacing for 4X8 glazed air collector?

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Posted by schooner on December 1, 2005, 8:44 pm
 
Does anyone have a good reference for proper spacing of the plate and
baffles for a 4X8 air collector?

Planning to take air in at one bottom corner and out at the other bottom
corner.  Plate spaced 2" from back of unit for airflow, 1" spacing between
plate and glazing.  One main baffle up middle splitting the 4' width and
then a cross baffle every 2' up the sides, with an 8" opening into next
chamber.



Posted by schooner on December 1, 2005, 10:34 pm
 
Here are two baffle design ideas.  One is just using foam baffles in the air
flow.  The other uses aluminum angle iron attached to the collector plate.
Was thinking this would both act as a baffle and also provide for better
heat transfer to the air.

Any thought?

http://www.corl.ca/drawing1.jpg

http://www.corl.ca/drawing2.jpg



Posted by Morris Dovey on December 1, 2005, 11:22 pm
 schooner (in 0UKjf.184344$Io.109023@clgrps13) said:

| Here are two baffle design ideas.  One is just using foam baffles
| in the air flow.  The other uses aluminum angle iron attached to
| the collector plate. Was thinking this would both act as a baffle
| and also provide for better heat transfer to the air.
|
| Any thought?

A bit...

It's probably worth pointing out that the objective is to get heat out
of the panel rather than achieve the highest possible temperature
inside the panel. Since warm air wants to rise, you're planning to use
electrical power to overcome what mother nature would've given you as
a gift.

High temperatures inside the panel promote losses. Lower temperatures
yield higher efficiencies. Baffles aren't the friends you seem to
think they are - seek to maximize the cross-sectional areas of your
plenum(s).

Angle iron/aluminum is (thermally) massy. If you want to use aluminum
as an absorber/heat exchanger, look for minimal thermal mass and high
surface area - and try to impede airflow as little as possible.
Warning: this is a non-trivial balancing act; but worth the effort to
achieve the balance.

A lot of experimentation went into the designs at the link below -
perhaps you'll find an idea or two you can use.

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



Posted by schooner on December 1, 2005, 11:40 pm
 Ideally yes I would take heat put at the top, but where this needs to be
mounted that is not an option.  I want to have the heat returned into the
ground floor and thus need to have the out at bottom.

Thanks for the info.  The baffles were meant to help disrupt airflow over
the flat panel, otherwise I assume it would be too smooth a flow and not
extract enough heat.  Using the angle iron or flanges was to help again in
heat transfer from the plate, not to hold the heat.



Posted by Tony Wesley on December 2, 2005, 5:22 am
 
schooner wrote:

I don't have any experience with this, so this is just a "thought
experiment" observation.  If you have to have the intake and outlet at
the bottom, I think you'd do better to have a straight shot from the
top down to the outlet.  In drawing 1, move your vertical divider to
the left, so that 85% (wild ass guess) of the collector's area is to
the right.  All of your baffles should be in that right-side region.

Does that make sense?


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