Clothes dryer heat recovery system

[Daox]

So, the attic project is winding down and I am looking for something new to do. I was reading a post here the other day about guys venting their dryers back into their houses and was thinking to myself how I wish I could do that. I don't think there is a day that goes by where my dryer isn't running in the winter. But, I have a gas dryer, so that isn't an option for me. Also, I'm not a huge fan of the amounts of water vapor is put into the air doing it. Especially when I think of the pains you go through trying to seal up your house.

So I was trying to think of a way to do this, and this is what I came up with. It really is pretty simple and eliminates the moisture problem. Start with aluminum dryer ducting and weld some aluminum fins on it. Thats it. You get yourself a relatively badly designed heat exchanger. But, its still a step up from aluminum tube, and a big step up from my current setup of wire reinforced plastic tubing. Perhaps adding a thermostatically controlled fan to blow over it when it heats up would increase efficiency.

Anyway, here are some pics.



Top view.

[cmittle]

I like the idea. I wonder if there's a way to attach the fins that would allow for people without a welder, but still maintain the conductivity.

Out of curiosity did you use Sketchup for the model??

[Daox]

I used SolidWorks because I use it professionally. I have played with Sketchup, but I'm far more proficient in SW.

I inquired with a few guys at work about thermal adhesives. I'm sure you could do it with a thermal epoxy of some sort. Welding happens to be easier for me.

[knowbodies]

That looks like a lot of work. Why not just hang your clothes to dry? Wire clothes racks are very cheap. Put it beside your furnace and your laundry will dry in a few hours.

[Daox]

My basement is pretty small and has a real low ceiling. I'd love to hang clothes down there, but it just wouldn't be real practical. If it was just me and my wife in the house I'd try to make due with lines downstairs, but we have five others in the house right now.

[Daox]

Here is the current setup. As I mentioned it uses the plastic/wire ducting which I hear is really not the best stuff to use period.








To the right of the dryer I put a temp sensor on the table (far right end of the table). I'll monitor the temps to see how cold it stays down there.

[dremd]

How about if you instal that heat exchanger in to a larger pipe, then used forced air to boost output?

[Higgy]

Not to sidetrack anything, but your basement looks like the inside of a Tatooine homestead from Star Wars.

...that is all.

[Daox]

dremd, I had thought about that, but I'd really like to keep this as simple as possible. Thats why I am considering just turning on a fan when the dryer is on. Thermostatically controlled would be great, but how hard would it be to just turn the fan on when you turn the dryer on?

I also talked to the guy who I was planning on using his TIG welder. He suggested looking for another way of putting it together as his doesn't weld aluminum very well. So, I'm looking into thermal epoxy and alternatives now. I did find this link while googling for thermal epoxy. Looks like a descent idea to me. Just have to make sure the epoxy will stick to aluminum.

Need Thermal Epoxy? - Make Your Own

[gascort]

Originally Posted by Higgy

Not to sidetrack anything, but your basement looks like the inside of a Tatooine homestead from Star Wars.

I was thinking, what a neat/weird looking basement too!

Daox, I have a better idea for you - I've been planning to do it all winter, but it's been super busy and I haven't even modded my car in months.

The way I see it, the dryer really has two problems.
1. you pump lots of humid, warm air outside, leaving lots of E to be recaptured
2. removal of air from your home = lower air pressure inside, inducing drafts until pressure reaches equilibrium.

Your method addresses problem 1, but not problem 2. my idea will attack both.

Use metal dryer vent, regular style with the ridges.
In the window where your exhaust air goes out, make another hole for an inlet tube.
Using some 2 or 3 inch pvc, set up an intake to draw cold outside air from a location sufficiently distant from the humid (natural gas exhaust in your case) air exiting your vent - maybe a meter or so?
Around the outside of your 4 inch dryer vent, (I think that's the size) install a 5 inch piece of hvac duct to run the straight length of it.
Connect your inlet tube to the 5 inch duct nearest the window, and ensure that the other end of the inlet is close to the dryer's intake.

Probably want to install a dryer vent "flapper" on the inside of the intake to ensure flow only during operation, and a screen or other guard on the outside to keep critters out. Probably also wrap the hvac duct in insulation.

You could make this design as simple or complex as you wish - from the other stuff you've gone after on your car, I assume you'd be going after the complex version.
For a simpler way, just use two pieces of long metal dryer vent and wrap them around one another - I don't know how well this would work though.

I got the idea from my background in biology and physics and thinking about countercurrent flow in fish gills / thermodynamic systems. Here's a wiki link.
Countercurrent exchange - Wikipedia, the free encyclopedia

I also plan on doing this with my furnace, which is a riskier proposition - need to keep the exhaust air hot enough that it still flows up the flue and out of the house, and also need to figure out what to do with condensation inside the pipe!