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Finsolar

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Reply with quote  #11 

I have built three pieces of similar hot air collectors like in this picture. They are very effective: with a fan on they produce even 100C or 212F air, when the temperature outside is minus 25C or -13F.

Two of them uses 25W duct fan, one of them uses 12v solar panel (computer) fan. The air flow is much better with 25W duct fan, and also air is much hotter. In my solution there's two layers of windows, and behind them I use black glass fiber textile through which air penetrates. 

2018-03-01_12-04-52  Today's work is finished.  Jaakko Laurila  Flickr.jpg  aurinkokeräin sivulta1.jpg 

 


gbwillson

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Reply with quote  #12 
Hi Finsolar-

Welcome! It's not surprising that the 25 watt duct fan out performed the 12v computer fan. Hopefully you can switch out the computer fans at some point. Having 200˚F temps in a collector is not only wasting heat, but will be harmful to a collector. What were the output temps of the duct fan collector versus the computer fans? And have you measured the airflow?
It's great to collect so much heat. 

I tested a basic 2-screen collector versus a hammock filter material. I thought the material would be perfect as it obviously has a lot more surface area to transfer heat than the window screens. It also added a LOT of resistance to the airflow. But even when I matched the airflow with the 2-screen, it didn't perform as I had hoped. I still have a large roll of the material in my garage if anyone wants to play around with it. How does it compare to the black fiber material you used?

Here is a link to my experiment:
http://simplysolar.supporttopics.com/post/2screen-versus-hammock-filter-matchup-7066650?trail=&highlight=furnace+filter#5

Greg in Minneapolis[wave]

PS:Nice thing about having three collectors the same size is you can experiment between the different units as long as you match the air flow. Once you have matched the airflow, the unit with the highest output temp is the winner.
Finsolar

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Reply with quote  #13 
They advertise those 25 watt fans move 9 cubic meter or 300 cubic foot in a minute. It is difficult to measure. Maybe some kind of a wind meter could be used? Well, I ordered a digital wind speed meter with laser pointer, maybe that is a nice toy 😉
gbwillson

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Reply with quote  #14 
With an anemometer, and a couple of thermometers, you can calculate the BTU output at various CFM outputs to find out which is most effective. Tests between collector designs can also be compared. I'm not sure why a laser pointer would be on a wind speed meter. I've never heard of that. I have an infra red thermometer that has a laser to show you exactly where you are measuring the temperature. 

Greg in MN
Finsolar

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Reply with quote  #15 
Yes, it is built in thermometer and anemometer. Price was not too bad, 35 dollars. Still in the post.
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