# duel test solar air heater



## Ky-Jeeper (Sep 5, 2010)

I'm working with Gary on this. Results are not done yet. I'm having to buy some wired indoor/outdoor therometers to get a better look at the performance of Box A and Box B. I will update this as soon as I possibly can. Here is some pics. Keep in mind this is made from mostly recycled items. I am building two huge collectors, they will be a lot neater with no wood. The best of the two test collectors will be incorperated in my permanet collectors. The two dayton 100 cfm fans are pushers on the inlet at the bottom of the heater box, not at the top as the pic shows.


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## Roadking (Oct 8, 2009)

Looking forward to reporst. I love the thermosiphon units I've built from Gary's site...they do great job even without fans.

Matt


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## Ky-Jeeper (Sep 5, 2010)

Yes the thermosiphon works fine on this. My big units will have to be ducted. Im not heating the rooms where the units are mounted. Test heater should be done Sat with the exception of having sun. Rain rain rain.


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## Ky-Jeeper (Sep 5, 2010)

Seems to be a shortage of wired indoor outdoor thermometers. I picked the only one radio shack had the other day and the display was almost solid 8's. Weather is to bad for testing anyway till later on in the week. 

I have lost contact with Gary on this project. I guess I will go it alone.


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## steff bugielski (Nov 10, 2003)

We have two of these, kinda these, in our living room.
We have them so that the in air is ducted to the floor of the room. The out air is 5 ft up. We also have a small computer fan that runs off solar mounted next to the out air to move it a bit faster.
It can be 5 outside and we will still get around 220 degrees coming in.
Sorry can not post pics.


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## steff bugielski (Nov 10, 2003)

What is the purpose of the screen?
I often thought of a HEPA filter since DH smokes.


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## Ky-Jeeper (Sep 5, 2010)

220* that's hot. You must have a really low airflow? The first black aluminium screen absorbs sunlight at a certain percentage. The second layer aborbs another percentage. The remaining percentage is nearly all absorbed by the black aluminium flashing back plate. With the radiant barrier attached to the poly-iso insulation reflecting any radiant heat back onto the aluminium plate. With the air free flowing throught the screens and on each side of the back aluminium plate most of the suns energy is efficiently removed from the heater into whatever I'm heating. The way it was explained to me if your glazing is very warm or hot to the touch your radiating heat back into the atmosphere. Made perfect since to me.


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## SolarGary (Sep 8, 2005)

steff bugielski said:


> We have two of these, kinda these, in our living room.
> We have them so that the in air is ducted to the floor of the room. The out air is 5 ft up. We also have a small computer fan that runs off solar mounted next to the out air to move it a bit faster.
> It can be 5 outside and we will still get around 220 degrees coming in.
> Sorry can not post pics.



Sounds Nice!

I agree with Jeeper on the temperature thou -- You would get more heat out of the collector if you could up the airflow so that the outlet temperature drops. 

Heat out is proportional to the temperature rise through the collector times the air flow volume. More airflow and less temperature rise will get you more heat out because the collector runs cooler and loses less heat out the glazing.

Gary


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## steff bugielski (Nov 10, 2003)

Well without the fan it hits 220. As soon as I turn on the fan it drops to 145.


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## SolarGary (Sep 8, 2005)

steff bugielski said:


> Well without the fan it hits 220. As soon as I turn on the fan it drops to 145.


That's good -- I thought it was giving the 220F with the fan on.

A good and efficient solar air heating collector will give about a 50 to 60F temperature rise under full sun conditions with about 2.5 to 3 cfm per sqft of airflow. The more airflow you have the more efficient the collector gets, but the temperature rise drops as the airflow goes up, and if the temperature rise drops too much, the air coming out of the collector does not feel warm.

Solar air heating collectors are about the only solar project I know of that can have a less than one heating season payback -- I don't think they get enough attention.

Gary


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## Ky-Jeeper (Sep 5, 2010)

Finally had a little time this past morning for full sun conditions. Keep in mind these test boxes are not insulated on the sides and is a single pane glazed glass with alum framing around the glazing conducting heat or cold what have you. Glazing had a very heavy frosty ice which I decided to leave on to defrost itself. Test box A melted the ice off first by about 5 min maybe ahead of Box B. This crude test was done outside with no indoor temps invovled and with fans running from the start. I will do acouple of more test before I decide on a final design for the 8'x 14' heater.

Fans on inlet temp f Test box A Test box B
7:15 29* 35* 38*
7:30 29* 32* 37*
7:45 30* 55* 54*
8:00 33* 83* 96*
8:15 35* 86* 104*
8:30 36* 91* 110*
8:45 38* 94* 113*

AT this point both test boxes pretty much peaked, So the fans was turned off. Boxs was designed for thermoshipion anyway. Testing was done in 5 min inentervals for the first 15 min because of rapid temp climb.

8:50 38* 121* 133*
8:55 39* 125* 140*
9:00 39* 128* 147*
9:15 41* 133* 149*
9:30 42* 138* 152*

At this time the test boxes appeared peaked. I headed to bed since I work nights. Woke up after this evening checked the max temp for the day.

Test box A Maxed at 138* box B Maxed at 157*. I am begining to think the heat needs to stay in the center layers area of the air flow areas away from the insulation and the glazing as much as possible. I will try to answer any question to the best of my ability on these two heaters. Again this is a very crude/basic test to just point out the diferences in the two box styles and both are very capiable of higher temps adding insulation to the sides for one.


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## SolarGary (Sep 8, 2005)

Ky-Jeeper said:


> Finally had a little time this past morning for full sun conditions. Keep in mind these test boxes are not insulated on the sides and is a single pane glazed glass with alum framing around the glazing conducting heat or cold what have you. Glazing had a very heavy frosty ice which I decided to leave on to defrost itself. Test box A melted the ice off first by about 5 min maybe ahead of Box B. This crude test was done outside with no indoor temps invovled and with fans running from the start. I will do acouple of more test before I decide on a final design for the 8'x 14' heater.
> 
> Fans on inlet temp f Test box A Test box B
> 7:15 29* 35* 38*
> ...


Hi Jeeper,
Interesting results.

It does seem like the box B construction is producing higher temperatures.

It would be nice if you could confirm in some way that the airflow on both is the same. As you know, heat out is proportional to airflow times temperature rise, so if box A is getting more airflow it might still be producing as much heat as B. Not sure how you would confirm the airflow is the same -- one of the little Kestrel type meters would probably do it, although you are probably at the bottom of its useful range. The Dwyer Vaneometer would do it if the airflow comes out the top vent in a horizontal direction.
Maybe identical lightweight streamers mounted in each outlet vent at the same place -- you could measure the angle at which the streamer hangs down with the air flowing and see if they are the same? If not, you could add a little flow resistance to the one that is flowing faster until they are the same.

The differences between A and B are pretty good sized, so even if the flows are a bit different, seems like B is doing better.

Please let us know if you do any more testing, or what you decide to build.

http://www.dwyer-inst.com/Product/AirVelocity/Vaneometers/Model480

Gary


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## Ky-Jeeper (Sep 5, 2010)

:bandwagon:I have another good set of results to post soon as I get a chance. My airflow readings are on box A 1.5 m/s flashing 1.6 at times. Box B 1.5 steady. I had found a few days ago that box B outlet is just alittle under sized. The remote wireless thermometer wasn't sliding in as easliy as box A. Box B outlet being a few thousands as in inches smaller may been the cuprit. Outlet vents are slotted at the very top of the vertical back side of the heater measuring 1"x14" which I read airflow with a anemometer. No shroud has been used if so I would probably see a much better airflow reading. I see no reason for airflow to be restricted in either box. The only limiting factor I see with either right now is inlet and outlet sizes, which can be easliy changed. As I noted in another post Box A defrosted itself maybe 5 min quicker. In both test just after sunrise Box A for about 10 min or so had a quicker ramp up time, but short lived. Box B aluminum back flashing plate could be downsized to mimic box A just alittle more but after the first few minutes of start up box B absolutely preforms very well. 

Im using two Taylor wired thermometer which max temp reading is 158 which box B done Friday.

I absolutely welcome anyone to try this back plate design. These two heaters are as identical as I could build them with the exception of the back aluminum flashing plate and the unpainted foil surface directly behind it.


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## Ky-Jeeper (Sep 5, 2010)

I do not know why the band wagon is on there LOL


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## Ky-Jeeper (Sep 5, 2010)

This past Friday the 2nd day of testing went well. I defrosed the outside glazing. The inside had some frost but was left to thaw on its own. Fans were left off till temperatures maxed out.

Inlet temp Box A then Box B
7:15 30 43 39
7:30 31 41 42
7:45 32 73 65
8:00 36 110 114
8:15 37 120 127
8:30 39 124 134
8:45 42 131 147
9:00 44 135 150
9:15 46 138 154
9:30 47 142 158

Temps peaked, fans on

09:45 48 112 133
10:00 49 109 131
10:15 50 106 130
10:30 51 97 125


Day one testing box B was110* difference between inlet and outlet air temps. Test day 2 they was 111* difference. Imagine starting with indoor.temps at or around 60*? Meaning I will have to open up the inlet and outlet vents for more airflow. I will have to think on this alittle more.


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## SolarGary (Sep 8, 2005)

Ky-Jeeper said:


> This past Friday the 2nd day of testing went well. I defrosed the outside glazing. The inside had some frost but was left to thaw on its own. Fans were left off till temperatures maxed out.
> 
> Inlet temp Box A then Box B
> 7:15 30 43 39
> ...


Hi Jeeper,

I guess this is with pretty close to the same flow through each box?

Certainly seems to favor the box B design and by quite a bit.

I'm a little surprised at the amount of difference, but maybe you have found a good design change with that back plate plus the screens.

Once the inlet temperature is warmer (say 60F) the temperature rise will not be quite as much as you will be losing more heat out of the glazing to the outside air. 50 to 60F is what most people air for.

Gary


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## Ky-Jeeper (Sep 5, 2010)

SolarGary said:


> Hi Jeeper,
> 
> I guess this is with pretty close to the same flow through each box?
> 
> ...


The difference suprized me also. I would like someone to build one besides me. I have one maybe two 3-D drawings in auto cad that I will post soon. Yes I espect the glazing to get hot. I will open the vents up to 21 square inches each from what is now 14 square inches. Then I will go from there. I definitetly don't want the heat building up in there. Last resort will be double glazing. I wish I had more time to commit to changing the back plate sizes and find the sweet spot.


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## Ky-Jeeper (Sep 5, 2010)

I will update this asap. I also failed to mention the alum screening is stapled to the sides and the top of the collector. no need for a screen frame on a test box. However the finished heater will have one for neatness. I did staple the screen at the bottom to the 1.5" wood spacers. The wood spacer that is attached to the wood frame in the drawing is actually in the wrong spot. from left to right it goes between the sec layer of screen and the poly-iso insulation.


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