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gbwillson

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Reply with quote  #161 
Bruce-

You are correct in that there is so much information available here on SS that it can be overwhelming. So it is good to ask questions.

A horizontal 6' high x 12' long ZP collector is going to give you a lot of great heat, regardless of a few branches. Add up the square footage of the shadows cast on our collector by the branches and subtract that from the total SF of your collector. So your 72sf collector might only be equivalent to a 68sf collector. Big Whoop! It's still gonna kick out some serious BTU's!

Is this collector going to mounted directly to the side of the house, or will there be some space between the collector and the side of the house? And if you make a 12' long U-shaped ZP collector having 3' wide channels would be the way to go. BUT...if you are wanting a 12'long collector with ducts at either end, you could get by with a single 6' wide channel. If high volumes of air are PUSHED into the intake manifold, the air will leave the intake manifold evenly side-to-side via the screen gap slot. I would suggest you use 8" of larger ducts as you will need an output of 400+ CFM due to the nature of the ZP.

So it sounds like you have a choice of a 6'wide x 12' long channel OR a 3' wide x 24'long channel with a return at the far end. Am I correct?


Greg in MN

Bruce

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Reply with quote  #162 
My plan is to build it out about 1/2 to 3/4 of the way under a 2 foot eave and gutter. I want to be out far enough to use all six feet that I have to work with without being shaded by the eave. I am going to attach it at the top with hinges so I can tilt the bottom back to the wall to get out of the summer sun under the eave. I don't know about tilting it out in the winter to get a better angle, but I might.  I have a double hung window at each end that I am going to run the 8" ducts through by replacing the storm window and one 9x12 pane of glass in the 6 over 6 window with Plexiglass for each duct. The intake and output can be in either or both windows. The wall is double course brick (with a one-inch gap between), steel lath and lime plaster, so I don't want to try to go through the wall! So my choices are to go out one window into a single 6' x 12' pass, or go out and do a horizontal "U"(across the bottom half and back the top half) to go into another pane in the same window, OR go out one window and do a 3 run (across the bottom, back the middle and over the top) to the other window. The ducts will come straight out the back IMG_0189[1].jpg  through the window behind the pentiums.
Bruce

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Reply with quote  #163 
For several reasons, I like the three pass idea...Easy to build with common screen sizes, two extra horizontal supports for the glazing and it seems to be stronger.  I might need another fan on the output side though.


 
Attached Files
pdf 3 channel.pdf (337.03 KB, 10 views)

gbwillson

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Reply with quote  #164 
That would work too. Just remember that every turn greatly increases the resistance. Don't make the collector box too shallow and make the turns wider, or more open than the straights for better flow like you have in the drawing.

Greg in MN
HauteGaronne

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Reply with quote  #165 
Is it a good idea in a U-turn or 3-run collector to let the screen frames go all the way to the turns, or is it better with a manifold there?
A manifold would give more room for the air to turn than if it's trapped between the screens.
Maybe without a manifold, it wouldn't stay trapped between the screens while turning and instead pass through the screens and instead return outside the air channel?
With screens going all the way you would maximise the absorption area though.
Has any testing been done on this?
gbwillson

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Reply with quote  #166 
No one has compared flow/performance rates on a ZP with screens in the corners versus no screens. My thought is that while you still want the turn to be wide, having screens in the turns will only serve to capture more sun. The worst that would happen would be the air might temporarily leave the screen gap as it goes around the bend. If in doubt, you could make the turn screen gap as a separate fixture and add/remove depending on performance.

Greg in MN

Something you might consider trying is to use fins, or vanes to help direct the airflow in the screen gap as air moves around the bend. Air would naturally bunch up as it gets to the corner. Fins/vanes might help the air spread out again as it leaves the bend.
HauteGaronne

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Reply with quote  #167 

I plan to have a plank as a divider in the middle to make the U-turn. 
If there is no manifold needed at the end I could make that dividing plank go all the way to the end of the collector, but with a slit in it at the turn matching up to the screen channel.
Would that be better than just having the divider end at the turning point?

KevinH

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Reply with quote  #168 
I don't know if anyone has done a U-turn ZP.  I doubt if the ZP flow could be maintained in a U-turn.  I would probably try an open plenum at the U-turn end.  On the side where the air reenters the ZP channel I would make it the same design as you did where the air originally enters the collector.  You could still put some screen in the bottom of the plenum.  Basically, the air exiting one side into the plenum pressurizes the plenum for the reentry into the return side.

When the air hits the turnaround, the flow will be the greatest around the outer edges.  If you just had a slit, there may be too much resistance.

I built a standard screen collector many years ago with a U-turn.  Sometimes due to different pressures or wind, the glazing would lift off the center divider allowing some air to bypass so make sure the design keeps a good seal to the divider.  I had to add an external means of holding the glazing against the divider.

Kevin H
MN
HauteGaronne

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Reply with quote  #169 
Thanks Kevin,
how was your performance with the slanted screen U-turn? I am wondering whether that might be better for U-turns than ZP
Gordy

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Reply with quote  #170 
How about something like this? Curved fins made out of flashing to help the air turn. I know the corners will be the hot spots, but I think that will be an issue with any U-turn setup. Shorter fins could be added in the corners like the one shown.

U-turn solar collector.jpg 


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Gordy,
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