Here's the pipe, covered in hose-clamped 1"x2" copper flashing for improved heat transfer. I have test-fitted a sample of the flexible dryer duct tubing that I planned to use to cover the pipe and fins.
Close-up of the fins and hose clamps. I installed 44 fins altogether, which added about 1" x 1.5" of extra surface area per side, each.
Counting both sides of the 0.020" thick fins, this adds 132 sq. in. to the copper pipe's area.
The 22 stainless steel hose clamps also added about 11 sq. in. of area.
The enclosed area of the pipe itself is 32 inches long, and with a diameter of 1.125" makes a surface area of 112 sq. in.
So the total area of metal-to-air is 255 sq. in.
The nominal 60/90 cfm fan I use to move the air, mounted to a bracket and adorned with a motto.
I needed to keep the air from flowing *into* the wall cavity, so I made a short bridge of ducting.
All ducting used in this project has a minimum interior diameter of about 3.5 inches. It's very corregated, so there must be a substantial amount of turbulence and drag as a result. I don't know what effect this has on the performance of the completed system. Anybody? Also, how can I measure the actual airflow of this system?
I made a gasket of aluminized bubble-wrap insulating material.
Here I have partially installed the ducting. I used wire cutters to sever the spring-steel spiral that gives the duct its rigidity so that I could wrap the duct around the copper pipe and fins. Fortunately, the aluminum wrapping kept the tube from collapsing.
Completed. I sealed the small remaining spaces and the cut seam with high-temp (max: 400 degrees) silicone adhesive from Devcon, which worked well.
