Clothes dryer heat recovery system

[charlesfl]

Has anyone considered removing most of the water with a high speed spin dryer?

Found a small one at:

Spin Dryer

[Xringer]

Wow, neat gizmo! Vid at The Laundry Alternative Spin Dryer - YouTube

[GaryGary]

Hi,

In this paper: http://www.ewp.rpi.edu/hartford/user...0Exchanger.pdf

They describe a counter flow heat exchanger that uses sheets of twinwall polycarbonate that are spaced about 1/4 inch from each other. Its efficient, and may be easy to make.

I'm having trouble figuring out how they get the air into and out of the polycarbonate sheets? That is, what is the configuration on the ends of the exchanger that allows them to separate the one flow that goes through the channels in the twinwall from the 2nd flow that is going between the sheets of twinwall?

I understand how the cross flow ones are setup with the channels running at right angles to each other, but I'm not seeing how they do it on this counterflow one.

If anyone has figured this out, please let me know.

Gary

[Daox]

It might be similar to this design. Every other slot on the side is blocked off on each end (and opposite on the other side). So, you have an intake/exhaust on each side, and each end. Seems like the cross flow would be a LOT easier to make, but this would be more efficient due to the counter-flow vs cross flow.

[Fornax]

Originally Posted by Xringer

Wow, neat gizmo! Vid at The Laundry Alternative Spin Dryer - YouTube

Those are neat, aren't they?

As one of the commentors on youtube mentioned they have been around in Europe for 80 years. Back in 1992 when I lived in a dorm we had one, third hand or so. 80 years ago people washed cloths by hand and this was a great invention to get them dry before hanging them out on the line. Our also third hand washingmachine in the dorm was also able to spindry, at 600rpm or so, so this separate spindryer was a big help.

Nowadays washingmachines do a good job of spindrying themselves, ours at 1400rpm. We then dry the clothing on a line (no dryer).

[GaryGary]

Originally Posted by Daox

It might be similar to this design. Every other slot on the side is blocked off on each end (and opposite on the other side). So, you have an intake/exhaust on each side, and each end. Seems like the cross flow would be a LOT easier to make, but this would be more efficient due to the counter-flow vs cross flow.

Thanks -- that heat exchanger is beautiful.

I like the counterflow in that it appears that about the best efficiency you can get from a cross flow is in the 60 to 70% range, and the counter flows can get up into the 80's. I have plenty of space for the extra length of a counter flow.

I did work out a way that I'm going to try. The twinwall pieces feed into a manifold at each end (one with a filter), and the spaces between the twinwall (which carry the opposite direction flow) are fed from the sides at each end.
I'll try to get a picture up later.

I've been keeping our power monitor on the dryer circuit since early 12/13 -- so far, it says the dryer has used 21 KWH -- not counting the energy to reheat the air the dryer pulls in from outside.
Our dryer pulls 4.5 KW when running with the element on. I believe that it pulls about 430 watts with element off, but need to recheck that.
It also appears to say that the dryer has a phantom load of about than 10 watts -- but, that may be the power monitor not getting zero right.


Gary

[eNeufenergy]

Hi, I'm new to ER but am quite interested in what is going on here. Our home energy use is similar with the electric clothes dryer being the biggest user, followed closely by the refrigerator. And since we live in the Pacific NW, outside clothes drying in the winter doesn't work. Drying indoors, since the humidity level rises so significantly creates other problems. I'm guessing that the energy that is expended to evaporate moisture from the clothes drying process indoors, well it's just one of those things where nothing is "free." One way or the other you pay for it.

All that said, I really like the HRV concept and I'd add or rather combine it with the barrel exchanger set between the dryer and the HRV. My suspicion is the difficulty is not in getting heat exchange, the difficulty is in keeping the heat exchange surfaces clean so they can do what they are designed to do. My reasoning: I would figure that by dumping the clothes dryer lint-filled, damp air into the barrel first would create a pressure drop, along with the significant temp. drop from the aluminum coiled tube that is bringing the counter-flow outdoor air towards the clothes dryer. So the pressure drop (like what a dust collector uses with a venturi upstream of the filters) would cause the majority of lint to drop out before it goes on to the secondary HRV. And, the moisture that would also drop out would act as a magnet for the lint. In other words, do everything you can to clean up the air and get rid of as much moisture you can before you run it all through the secondary HRV. The HRV would be incredibly difficult to clean and the barrel would be comparatively easier; insulate and incline the barrel, put a drain hose on one of the bungs and have access to the lid so you can pull the offending lint off the coiled aluminum duct to get a good exchange.

I'm motivated enough to give this a try.

[GaryGary]

Hi,

Here are the pictures of the "throwaway" prototype of the dryer heat exchanger

Untitled 1

Any suggestions would be appreciated. I do know already that its ugly

---
That's an interesting thought on the barrel filter.

I guess one thing I'll learn on the prototype is how good a job the filter does in keeping the HX clean (or not).

Gary

[eNeufenergy]

I'm not allowed to post the link since I'm a newbie so check out: FEMA Dot GOV the doc. is "Clothes Dryer Fires in Residential Buildings (2008-2010)"

Some useful stats. to consider:

Findings
■ An estimated 2,900 clothes dryer fires in residential buildings are reported to U.S. fire
departments each year and cause an estimated 5 deaths, 100 injuries, and $35 million in
property loss.
■ Clothes dryer fire incidence in residential buildings was higher in the fall and winter months,
peaking in January at 11 percent.
■ Failure to clean (34 percent) was the leading factor contributing to the ignition of clothes
dryer fires in residential buildings.
■ Dust, fiber, and lint (28 percent) and clothing not on a person (27 percent) were, by far, the
leading items first ignited in clothes dryer fires in residential buildings.
■ Fifty-four percent of clothes dryer fires in residential buildings were confined to the object of
origin.

And it appears the big take-away is that, as a system, a clothes dryer is inherently unsafe (with standard gas or electric elements) as there are no adequate, simple, or passive ways to keep the thing clean. The dryer manufacturers appear to send the problem "downstream" to the ductwork and pass the blame onto something they have no control over.

Bullet point #4 above: At least the saving grace here: you are likely to not start a clothes dryer fire if you are wearing clothes while you are in the dryer.

Thanks

[Xringer]

Since these aluminum ducts get quite warm when the dryer is running,
what about building a long duct/box abt 10 x 10 inches around the dryer duct?
Maybe construct the box from coroplas or even some cheap wall paneling.

Then pump air into one end of the box, and let it exhaust at the other end..?.

Kinda based on the lab condenser idea..


With the right amount of air flow, you should be able to keep some of those BTUh indoors.

Efficiency might not be that great, but it should be able to pay for the power it uses.

A few free BTUhs are better than zero BTUhs.