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gbwillson

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Hi gang-

Over the weekend Krautman and I started working an interesting little experiment I brainstormed where we test the ZP using various screen gaps openings at the same time. I wish I had thought of this test a few years ago...[frown]

My original prototype ZP had the ability to adjust the screen gap with a few screw turns. Seatec made a ZP with an adjustable screen gap as well. The problem with adjustment tests is you are never able to test one screen gap size directly against another. It can take a few minutes to change the gap size, in which time the sun angle and conditions will have changed.

Krautman's ZP #2 will be mounted on the roof before fishing season, so before it is, we thought it would be a good idea to test to see if we can find an ideal screen gap for this collector. It currently has a screen gap of 1⅜". Krautman thinks this is too large, but couldn't specifically answer as to why. So we thought it best to get an answer before the unit is on the roof. So the setup is this, we are making a 16' ZP, with three separate channels, roughly 8" wide. All three will share a common intake manifold, have separate outputs, and each test channel will have a different screen gap. Theoretically, if the output flow in each is the same, the gap with the highest output temp is the winner. However, it is very possible that the output CFM is different between channels, due to gap size differences. The first round of gap sizes will be 1", 1.25", and 1.5". We will then run the test again, if needed, to narrow down the results further. 

Keep in mind, this is for a 16' long collector with a high velocity output. So a differences in size and CFM will likely yield different results. Weather permitting, we hope to have the unit complete by next weekend, so if you can think of a test you'd like to see us run, let us know...



Greg and Krautman Craig in MN

Bert

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Will be interesting to see those results for sure.
I would like to see a test with maybe 1.5 to 2 inches for the outer screens with a third screen halfway between them. The middle screen may have to be frame-less.
That may be hard to do with your particular setup though.



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Bert K.
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gbwillson

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I like that idea Bert. Once we have narrowed down the "best" screen gap, we may think about comparing it to a three screen ZP gap. And for testing, all screens will be frameless, in that they will simply be stapled to spacers along the sides of the test channel.

Greg in MN
gbwillson

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Hi gang-

We're a few days behind schedule, but I expect us to be ready to test by the end of the day tomorrow. But after tomorrow there are at least two days of we weather ahead. But at least we will be ready! Using scraps and badly warped wood has been a HUGE pain! The test unit is 16' long, and ended up being 30" wide. With each test slot being 9" wide. The back screen layer is on and all the pieces of screen for the upper layer are cut and ready to be placed. In order to save wood, small chunks of the proper size to make up the various gap height were nailed to the sides and the upper screen will be fixed to them. We also still have to attach the restriction gates to even out the flow between the lanes for testing. 

And if you notice, we have two intake ducts. Craig prefers entering the collector from the end and I prefer the back entry, which works better for my mounting setup.[biggrin] So now we can see how the two entry points compare CFM-wise. Should be interesting...

Greg in MN

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KevinH

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For the end versus back duct entry I think it is more about how that decision affects the other ducting and how the collector is mounted relative to the house entry points.  On mine the entry/exit are at the end.  If they were on the back a 90 degree turn would have been required.  For a collector mounted on a wall it would make more sense to exit out the back.  Still, it will be interesting to see what effects the entry method has, such as if it affects how even the flow is through the 3 channels.

I assume you are pushing the air so the outer channels will get more CFM, but that can be adjusted for the test.

Kevin H
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gbwillson

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Kevin-

I don't think entry matters at all as far as performance overall. But Craig is convinced you can put more air through the collector from the end entry. In either case, the intake manifold will have a positive pressure allowing the air to flow evenly as it entered the screen slot. And with the end entry, you will need a deflector of sorts to prevent the incoming air from shooting right down the middle of the screen slot. While a back entry needs no deflector.

We are pushing air for our test, but I don't think the outer channels will have more air flow. I think the larger the screen gap is will have more air flowing through it as it has the least resistance. So I fabricated a "shutter" for the largest two channels so they can be restricted as needed to match the airflow of the smallest gap. Once all channels have the same CFM output, the one with the hottest output temp "should" be the winner!

Greg in MN
Rick H Parker

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If you offset the entry and exits ports so that one aligns with the top channel and the other aligns with the bottom channel ( Put the ports in diagonally opposite corners)  The port to port length, through each channel is the same and the flow will be even. 

Not sure what I mean, Take a piece of graph paper mark off a grid, any size. Starting from one corner calculate the length of all the direct paths to the diagonally opposite corner, Direct meaning every move must bring you closer to the diagonally opposite corner, no back tracking. Your discover all direct paths are of the same length.

Rick H Parker

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Rick H Parker
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Rick H Parker

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"And if you notice, we have two intake ducts. Craig prefers entering the collector from the end and I prefer the back entry, which works better for my mounting setup.[biggrin] So now we can see how the two entry points compare CFM-wise. Should be interesting..."


Once everything is factored in. I'll place my bet on stalemate.

The air coming from the house has to be turned into the collector, air from the collector has to be turned into house.  For it to be a fair test, your need to add a 90 degrees turns to Craig's intakes.

It does not matter where the turns are done, the over all effect will be the same, that is why I am betting on stalemate.  

Rick H Parker


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Rick H Parker
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gbwillson

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Rick-

That is EXACTLY what I tried to explain to him. While back entry air does have to turn before entering the screen slot, the air is swirling in the intake manifold before it does. Entering from the end means you have to use a highly restrictive elbow, fitted to a restrictive 2.25"x14" duct just to get into the collector. Then place a deflector in front of the incoming air to prevent the air from shooting straight into the screen slot. One of the duct adapters(Corner Boot) he used has an equivalent length of 80' of straight duct. Now add another 20' EL for the 2.25"x14" straight boot and he now has added the EL of over 200' with just these 4 duct pieces! I did manage to persuade him to try something different on his latest ZP build. 

AND...I think rear entry looks a heck of a lot better, or at least cleaner since any duct work is hidden from view by the collector, or inside a wall. In any case, both will move air in one end and out the other, so all is good.

Greg in MN
Rick H Parker

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"Then place a deflector in front of the incoming air to prevent the air from shooting straight into the screen slot. "

Good point, The end port is going to place uneven dynamic pressure pressure on the channels. Coming in from the back would put zero dynamic pressure on the channels and a even static pressure ... Not ideally but close enough.

Rick H Parker

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Rick H Parker
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