I can’t call this a heat exchanger, as it doesn’t exchange any heat. It just sheds some of the heat from the dryer duct into the room. I am trying to keep some of the heat I paid to create, in the house, where I tend to hang out when it’s cold outside.
I know I’d get better return on the money I spent by feeding the dryer outside air, but I wanted to give this a try. A friend gave me the heat sinks, so I wanted to see if I could find a noble use for them. I love DIY projects anyhow. I kinda liken it to a homemade energy themed work of art.
A picture is worth a thousand words, so here’s a 25k word novelette. (Hey, technically these stereoscopic photos are 2 photos each, so they count double. Just cross your eyes to get your word-count’s worth.).
I currently have 20 of these heat sinks. I fiddled around with them for a while to see how many I can fit on my duct, and I came up with 74. Two rows of 15 down the long, wide face with 14 spaced in between and a row of 15 down each side.
I figured I’d start with the 20 I have, and see if it does anything for me at all before I mangle that many heat sinks.
I rather like this dense arrangement. I’ve knocked all the cooling fans loose for now. I may re-install some of them. Possibly just down the center row maybe? A larger box fan running off the dryer’s timer may work better in the end.
I ended up drilling all the holes with a drill bit from the back side where I had my layout marks. I then de-burred the holes from the front, pushing hard, so I dimpled each hole. This flexed the metal so that the screws would tighten the sheet metal up to the heat sink.
The screws I used where some pan head self tapping sheet metal screws. Ended up not needing the self tapping feature as I had to pre-drill all the holes to keep the metal bits from preventing the heat sinks from coming up tight to the metal. Live and learn. I just ran them between the fins on the heat sink. They seem to hold tight. I hope that if I ever disassemble this thing, I can reuse the heat-sinks in the future. Maybe. Please?
It’s actually surprising how heavy the assembled unit is. A lot of light weight parts makes for a heavy finished product.
Carbon Monoxide poisoning is a risk when doing something like this, so the whole contraption is sealed up tight. I’d feel really bad if I killed myself trying to save a buck.
I tried to keep the inside of the duct as smooth as possible to not collect any lint and cause a fire hazard. I am hoping the shallow screw heads will create just enough turbulence to keep mixing the hotter air with what’s already shed some heat to the walls.
Now I just need to add 2 stainless steel housed thermistors so I can monitor the air intake and exit temperatures. If I see a temperature difference, that means it’s working. I can use a 55 gallon plastic bag to figure out the air flow of the dryer. Some magical maths will tell me how much heat I am dumping into the house vs throwing out with the wash-water (clever, eh?). If I get any good results at all, I will try to collect enough heat sinks over time to finish this project.
54 more heatsinks needed. New price for these appear to range between $10 and $100 (Seriously?!?). Glad I am not damaging the heat sinks too bad, but the dollar value of this project kinda makes me a little sad.