There's just something about free that I really like, especially when it's free energy. I designed this heat exchanger that takes in zero degree air and puts out 130 degree air absolutely free of charge. And it's made from beer cans and downspouts!
There are other designs on the internet. I've tried them and trust me, they're all flawed. I swear I can find a design flaw in virtually everything made.
Most collectors utilize either aluminum cans or downspouts for the collectors and manifolds but those designs are incomplete. If you use only aluminum cans for the collectors they will absorb quite a bit of heat but as soon as the fan turns on, the cans will cool off. The thin walls of the cans do not provide enough thermal mass to hold the heat and provide long term energy. If you use only downspouts for the collectors, there will not be enough resistance in the air flow to fully absorb the warmth from the aluminum. My design combines the two.
First, we must drill a 1 1/4" hole in the bottom of the aluminum cans. I have found this is a good size hole for passing the warm air. Of course, the hole in the other end is the can opening, approx. 1" or less so theoretically a 1" hole would be adequate.
The cans are then stuffed inside a standard 2"x3" residential downspout, stacked on top of each other. This completes the collector tubes.
We utilize 3"x4" commercial downspouts for the intake and exhaust manifolds. The exhaust can be moved to either end or anywhere in the middle, whichever accommodates the final installation the best.
This design is the correct size to use a standard sliding glass door panel for the insulated glass cover. Every glass shop will have a couple scratched ones laying around you can get for free or cheap. God, I love free & cheap.
For the fan, I used a 110 volt 6" duct fan that I bought on Ebay for $20. This is tied to a thermocoupling that turns on at 120 degrees and shuts off at 90 degrees.
It works great, I hope you can use this!
Solar Hot Air Collector Cross Section
Solar Hot Air Collector
Solar Hot Air Collector Layout