closed dryer heat exchanger?

I have been looking for something that probably doesn't exist for reasons I don't know.
I am trying to find out if there is such a thing as a heat exchanger for a dryer that would attach like a humidifier to a furnace?
I have read MANY posts and articles about just piping the exhaust of the dryer into the house and how bad that is with lint and moisture.
What I am looking at is something like an air-air exchanger where each "circuit" is closed.
So the dryer would still exhaust outside but on the way it would flow through a box that is on the cold air return of a furnace. The furnace would suck air through the box and collect some of the heat.
Just curious if anyone has ever seen anything like this, if it is even feasible, and what issues this would cause?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Here's a thing you can use with an electric dryer, to provide warm moist air in the house. I wouldn't use it for other than winter months: http://www.improvementscatalog.com/home/improvements/75991-indoor-dryer-vent.html
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

They suck. They invariably fill the room with dryer lint.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

For an electric dryer, all you need to do is filter the exhaust and distribute it somehow. A high efficiency furnace filter in an appropriate enclosure would probably do the job without createing too much back pressure.
Don't do it with a gas dryer.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

What it'll do is clog up within a few hours and then damage your dryer.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

A furnace filter? There are many square feet of element there. I don't think so.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mar 25, 12:02 pm, snipped-for-privacy@gmail.com wrote:

As a mechanical engineer, I have thought about it for a long time
buying, if available....haven't seen one
OR
building one...haven't done it for a number of reasons
I live in SoCal so my heating demands are not all that high. the temperature differences involved are pretty low so heat transfer won't be great, the air stream is a little dirty (so maintenance will be an issue), air stream contains mositure so condensation, corrosion & freezing will (can) be issues. The heat ($'s) saved (at least for my potential installation) won't justify the cost. My laundry room / porch is tiny and incorporating a heat exchanger into the system would be a lot of work.
This does
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Living in ND and having 4 kids I think our dryer is on all the time! So if this would work I could reclaim a lot of heat.
Yeah I have tried to think of those issues too (plugging and condensation). I was thinking of some kind of filter where the exhaust goes in and a drip pan like thing for condensation. Kind of like an AC coil some how collects condensation.
One thing that would be nice with my design (if it would work at all) would be that it would work on a gas dryer too. I was planning on no mixing of air flows. Like an engine radiator, the antifreeze is separate from the air.
The amount of surface area needed would probably be immense and would that slow the exhaust air flow down too much? Not sure.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Living in ND and having 4 kids I think our dryer is on all the time! So if this would work I could reclaim a lot of heat.
Yeah I have tried to think of those issues too (plugging and condensation). I was thinking of some kind of filter where the exhaust goes in and a drip pan like thing for condensation. Kind of like an AC coil some how collects condensation.
One thing that would be nice with my design (if it would work at all) would be that it would work on a gas dryer too. I was planning on no mixing of air flows. Like an engine radiator, the antifreeze is separate from the air.
The amount of surface area needed would probably be immense and would that slow the exhaust air flow down too much? Not sure.
*************************************
Without a lot of pre-filtering, any small sized heat exchanger that could do this would quickly plug up. Condensation in the exchanger would produce an ideal environment for bacteria growth, which would need to be dealt with.
One could run the exhaust through a very large area filter and into a large duct, say 6" with very well sealed joints so condensation cannot leak through the joints. It could run across the basement in the joist space from one side of the basement to the other, sloped so the water would run down to the far end and out of the house. Around this duct, would be another, say 8" in diameter, with a blower blowing room air from the far end to the dryer end between the two ducts, forming a counterflow heat exchanger.
By using an oversized duct, the extra length should not cause dryer problems. I suppose that the filter could be eliminated if the inner duct were frequently cleaned. Without cleaning, the pipe walls would gradually become insulated with link, and lose effectiveness. Cleaning could be accomplished with a 6" plastic chimney brush, run in from the outside while the dryer runs on an air cycle to blow the loosened lint out. Lengths of 1/2" PVC pipe with male/female threaded fittings on opposite ends make an excellent, cheap chimney brush handle, by the way.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 25 Mar 2008 12:02:17 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

-snip-
I know I've seen this setup for stovepipe over a wood stove- and I *Think* I've seen the same setup for dryer vents. It is a box- say 14" on each side- with ? 1" ? pipes through it, open on each end. Perpendicular to them is the inlet and outlet. . . . . . .
Here's the stovepipe one- http://www.transoceanltd.com/appliances/stoves/magic.htm
The ball in the center is attached to a scraper that you clean the pipes with occasionally.
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Dryer exhaust would not be nearly hot enough for one on those to do much.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mar 25, 3:02 pm, snipped-for-privacy@gmail.com wrote:

I've always wanted to build a heatless clothes dryer. It would just be a large air tight container you fill with clothes, seal up, and then evacuate all the air. Under a vacuum, the water would boil right out of the clothes with no more than ambient heat. It wouldn't need any moving parts other than the pump.
Might wrinkle the clothes a bit.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The Reverend Natural Light wrote:

It's called freeze drying.
a
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 25 Mar 2008 12:02:17 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

The things are between 5 and 10 dollars. Why not buy one and see if you have the problems that others report, or if everything goes well, like for me.
I've read those warnings too. My diverter box or whatever its called has a lint filter, a 5x5" piece of something like window screen, and I never see any lint coming out or lying beneath the outlet. I've been using it for 24 years with no problems. I clean the filter about every 30 loads, or when I see that it is partly clogged. It doesn't clog very fast becaue there is already a lint filter in the dryer. They sell such things at HD but they can be hard to find.
As to moisture, you need more moisture in the winter. That's why they put humidifiers on furnaces.
Maybe if I had babies and did 3 loads of wash a day, I would have problems, but a) I doubt it, and b) then I could switch the diverter some of the time to send the air outside.
Trying to understand the other posters' claims of lint, maybe they dry more lint-bearing laundry than I do. I don't actually know what fabrics generate lint and what don't, but I do use a variety of fabrics. The lint filter in the dryer whistles when it gets full.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@gmail.com wrote in

One thing that would recover the heat is too duct the dryer exhaust to an HRV - Heat Recovery Ventilator. There would be a few problems to solve the main one being that HRV's use very narrow spaces for air flow and lint would plug them in no time at all. So you would first have to design a way to clean all lint from the air - screens and filters. HRV's have filters in them but they couldn't handle dryer lint without plugging right away.
HRV's accomplish the heat exchange by running in and out air through narrow spaces, alternating warm and cold spaces so the incoming air channels have an out going air channel on both sides, etc. The spaces are about 1/16 th inch wide by 12" by 12".
Another major issue would be balancing the airflow into house with airflow out - HRV's have 2 fans, one blowing in and one blowing out and they should be balanced fairly closely or you compromise overall house ventilation with all of the attendant problems.
Up here, in Canada, HRV's cost around $800 plus installation.
I once thought I could design an HRV myself but there are way too many issues to deal with, especially up here where winters are -20 to -30 C for 6 months. I have a 2 heat exchanger geothermal heating system with 2 HRV's and they work great - house humidity is way too low in the winter if I run them too much. MY HRV's come with defrost settings if the incoming -30 air tends to freeze the units, drains for condensate, timers built into switches and the dehumidistat, insulated ducting, etc. Fairly complicated. They are claimed to be about 80% efficient.
You could look for a commercial HRV - maybe there is such a thing - there must be an application requiring wider slots. The slots are in the heat excahnger which is removable for cleaning. Mine are plastic so I clean them with a pressure washer. If you had enough screens and filters maybe the lint problem would be reduced so cleaniong the exchanger every once in a while would be feasible. On mine the slots are so narrow and long that I couldn't blast clumps of lint out.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.