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solarusmc

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Reply with quote  #41 
Dan

who are you talking to? GG? or me?

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Pat B. Warwick, Rhode Island Rest Assured! Comments and/or suggestions I make here at the forums on 'your' projects as well as my own have all been carefully and scientifically calculated by the 'seat of my pants'

Garage_Hermit

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Reply with quote  #42 
Hiya, Dan !

Good points, as usual !  (I guess they were meant for me !) [tongue]

Originally, my collector was designed to go on a south-facing facade, bolted to the wall, at ground level.

The air input and offtake both enter & exit at the bottom, on the side, after running about 8 foot from a window also at ground level.

The advantage in this configuration was that the airstream only has to take one 90-degree bend (left, out of the window).

When the air enters the collector, it is already parallel to the bulkhead, so no more twisting and turning to do...
(it just has to do its upward and downward gymnastics bit, around the baffles...).

However, like you say, the vents could come directly in from the back, and go out via the back...
Nonetheless, in this case, the incoming air would be "colliding" with the bulkhead, this could generate turbulence... Therefore I see the collector needing to be DEEPER in this case...

(in fact, this was one of my (unexpressed...) criticisms of Solar Marine's "thru-the-back narrowish-box" approach: I suspect that airflow impact of this nature could be detrimental to performance...) (sorry, Pat !).

The input/offtake could also come in through the bottom, and go out through the bottom.
In any event, they will generally be in the same plane, given the airflow needing to perform a "180-degree turn". 
==============
One advantage of the backpass that I did not mention is, the bulkhead can be "fabricated" from lots of diverse materials, such as a sheet of steel, or zinc, or aluminium.
It could also be made by bashing flat some old metal shelving, and pop-rivetting it together etc.  An old refrigerator would also work, or even a series of metal bar trays, all taped together using aluminum duct tape etc.
In other words, "local supply".   Whereas screen, dryer duct, downspouts etc. might not be available to everybody...
======================
In other variants, one could imaging building a backpass collector onto the side of an old VAN...
Preferably a black vehicule, parked facing east or west...
(A 1959 12-cylinder Dodge Bread Delivery Truck would be fine...).

You would just constuct a deepish frame comprised of some strips of styro onto the outside of the VAN, using double-backed tape.
Then you would saw a hole thru the upper side of the side of the van, inside this frame, to let the air through into the VAN interior.
You would then need to glaze the side of the van -- this could be done using either a matrix of salvaged windshields, or by simply parking the van alongside a windbreak as commonly found at a Car Wash, for example.
(any residual gap between the vehicle and the carwash windbreak being caulked using extra thicknesses of polyiso, jammed between the van and the glass windbreak...), or bales of hay...  Dictionaries and old newspapers would also do the trick...

The HOT (very...) output air could be drawn off through the passenger door window, and if necessary ducted using a series of plastic buckets with their bottoms cut out, and all stacked into one long length, to make a very efficient and insulated conduit.

Beer kegs of water could be placed on the van roof, to form an hydronic generator.
However, that variant is somewhat off-topic, so I shall now stop...

Have a nice weekend (It Was a Very Long Week...) [sleep]

G_H




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(1)  "Heat goes from hot to cold, there is no directional bias"
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solardan1959

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Reply with quote  #43 
I was modeling it on ggtaft's design and was referring to his outputs.  Was not sure what he was going to do with them but can see the benefit like he and Hermit said  with not colliding with the front and back as it enters or exits the vent.  The problem with thicker is if it is too thick the air might not run close enough to the heat source and not extract it properly.    

Hermit, you would be hard pressed to find an old Dodge van that was not rusted away, and 12 cylinder? I think the most they had was 10 here is one of their more out there models, the 10 cylinder Tomahawk!
   [image]
You'd be hard pressed to build a collector out of that also but it would generate some serious heat...
Dan
Garage_Hermit

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Reply with quote  #44 
Thanks, Dan !

I found one - B300 Tradesman van

(note Mr Bow-Tie Solar Designer coming out of shop, with nice new rolls of MESH...) [biggrin]

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(1)  "Heat goes from hot to cold, there is no directional bias"
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solarusmc

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Reply with quote  #45 
Got what you're saying Dan and G_H,

being to thick/deep may screw it up a bit.

I like the supply/return coming in from the side.
Makes a lot of sense on air flow.

The air would probably circulate nice using 1 fan without a glitch.

Can't wait till he puts this unit together and gives us all feedback.

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Pat B. Warwick, Rhode Island Rest Assured! Comments and/or suggestions I make here at the forums on 'your' projects as well as my own have all been carefully and scientifically calculated by the 'seat of my pants'
Scott Davis

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Reply with quote  #46 
Hi Pat,

Your dual pass (not really a backpass since air is also in front of the absorber) is an interesting design that might perform really well.  It gives two opportunities to scrub the heat from the collector, which should give it a nice advantage.

I would suggest first introducing the coldest air from the house near the glazing and let it return behind the collector.  That will keep the hottest air away from the glazing and reduce heat loss out the glazing. 

Your design is definitely worth a side by side test to the double layer screen reference standard to see how it compares!  Please let us know what develops!
 

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ggtaft

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Reply with quote  #47 
I am curious if anyone has ever used aluminum heatsink material for an absorber the kind with the fins like the kind that a gas engine uses (briggs and stratton or tecumseh) not from these engines but the same kind of idea where the air would have to run through the fins?  I think this would add more surface area that the air would have to touch to extract the heat.
solarusmc

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Reply with quote  #48 
Scott, thanks for your input and I agree with the air routing you mentioned.

Did I call my drawing a backpass? Jeesh.. sorry about that. I meant 'double pass'
It allows me to draw the room air in high on the backside, send it down around the absorber and exit thru the Supply hole up top backside. It should basically stop like 99% of the cold air backdrafts I'm hoping.

I also like the simple empty black box with aluminum absorber plate, 2 holes at the top with a vertical baffle dead center inside forcing the room air to go 'down' and around the baffle before exiting up to thru the Supply hole. Just makes a lot of sense. 

Back to the Double Pass Design.
If I build one of the double pass type collectors which I most likely 'will' before long I really want to stick a single layer of screen on top of the 'front side' of the absorber sheet metal so the angled sun hits woven aluminum strands all hours before and after 12 noon.

I have a hunch the collector will heat up 'quicker', stay heated longer and possibly create a bit higher temps then the single flat plate aluminum sitting in the box.

I'm already designing the frame work to use to keep things simple as possible during construction.
Probably go with 2 x 6 metal stud framing for the outside frame and 2 x 3 metal stud frame inside to attach the absrober plate to. That should give it even space on either side of the absorber plate, ya think?

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Pat B. Warwick, Rhode Island Rest Assured! Comments and/or suggestions I make here at the forums on 'your' projects as well as my own have all been carefully and scientifically calculated by the 'seat of my pants'
gbwillson

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Reply with quote  #49 
Quote:
Originally Posted by ggtaft
I am curious if anyone has ever used aluminum heatsink material for an absorber the kind with the fins like the kind that a gas engine uses (briggs and stratton or tecumseh) not from these engines but the same kind of idea where the air would have to run through the fins?  I think this would add more surface area that the air would have to touch to extract the heat.


I hadn't thought about engine fins, like on my old air-cooled VW. You might be able to scrounge from a junkyard for really cheap. I did wonder the effectiveness of a panel that was covered with computer heat sinks. if they were all painted black and you channeled the air the flow through and over them it might be worth testing. Tests have shown that fins are a very easy way to increase the effectiveness of almost any panel. Heck, I bet a almost all of us look at everything as a possible collector. 

Greg in frigid MN [wave]
Scott Davis

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Reply with quote  #50 
Pat, yes, great thinking!  Adding the benefits of the slanted screen to the front of the collector will aid heat transfer, keep the hotter air away from the glazing and further enhance its performance, no doubt!  This design is sounding more and more interesting!
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