Clothes dryer heat recovery system

[Piwoslaw]

Originally Posted by 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.

We have a clotheshanger over the bathtub in the upstairs bathroom.



Each of the 6 poles has a string in it which goes through a pulley, allowing it to be lowered or raised. It doesn't impede bathing too much, especially since we usually take showers in the downstairs bathroom. The evaporating moisture helps humidify the house (and condense on the windows ).

[fike]

Originally Posted by Daox

Welcome to the site fike.

If you cool the air too much you'll get condensation. Not that you can't deal with it, but you'll have to make accommodations for it.

Thank you for the welcom.

Yea, I guess there would be condensation, but I am not sure that it would be very harmful in the long run. I would guess in 2 years or 10 years (I have no idea how long) the duct would rust out. If it is 2 years, it probably isn't cost effective. If it is 10 years, it is probably a good idea.

I also considered putting a damper switch to direct it through a short direct route in the summer months and a long and meandering route in the winter months.

[Daox]

To lengthen the life of the system you could of course use aluminum ducting.

I'm not sure how bad it would be, but condensation would lead to lint build up I would think. Wet lint would hold moisture and lead to mold problems. I'm not sure how bad it would really be, but thats another thing to look out for.

[fike]

Originally Posted by Daox

To lengthen the life of the system you could of course use aluminum ducting.

I'm not sure how bad it would be, but condensation would lead to lint build up I would think. Wet lint would hold moisture and lead to mold problems. I'm not sure how bad it would really be, but thats another thing to look out for.

I thiink if you keep the lint filter clean, it shouldn't be a problem. The exterior vent doesn't show any buildup of lint, so I would assume it is pretty lint-free.

[Daox]

You must have a cleaner/newer dryer than mine. Mine has lint all caked to the pipe walls. Not a ton, but its there.

[NeilBlanchard]

Hi,

I think a large filter is the way to go, since you would recover ALL of the heat, and you would get the moisture as well. In the winter time in heated houses, the air gets very dry without some way of humidifying it.

We has a gas dryer, so maybe a carbon monoxide sensor would be a smart thing to have?

[Daox]

Good to see you over here Neil.

If you were to vent directly into the house, I would imagine a carbon monoxide sensor would be absolutely essential. Dryers go through quite a bit of air. I don't even know if it would be possible to vent it directly into the house without major air quality problems.

[Xringer]

IMHO, dryers and gas hot water heaters could be a dangerous combo..

I noticed in my daughter's basement, a gas hot water heater with a PVC air input pipe.
There was a second PVC pipe for the warm exhaust gas.

I wondered if there was an air source for the dryer. Didn't see one.
When the electric dryer was running, it seems to be sucking air from the both the PVC pipes going to the hot water heater.
So, what comes in when the heater is burning gas, while the dryer is running? Exhaust gas?

[ynot7201]

I am starting to work on a system that encloses solid aluminum pipe (instaed of flex). Then surronding this with a box, and air circulating from on end to the other thus taking heat from skin of pipe .no damp air or lint problems ..I hope it works!!

[Christ]

Originally Posted by ynot7201

I am starting to work on a system that encloses solid aluminum pipe (instaed of flex). Then surronding this with a box, and air circulating from on end to the other thus taking heat from skin of pipe .no damp air or lint problems ..I hope it works!!

This is exactly like an air to air intercooler, but will not be as efficient as a bar/plate design. Skin xfer of heat is limited to surface area, and the smaller your pipes are, the more surface area there is to xfer heat from one medium to the next. Bar and plate is one of the most efficient because there is a tradeoff between thermal xfer efficiency and pressure drop, and many of the best intercoolers on the market are borderline at 80% efficiency (of this type of design).

Also, keep in mind that the more heat you extract from your exhaust, the more you slow it down, making it more difficult for the intake fan to blow air through the dryer, and more difficult for the moisture to leave. The idea is to snake as much heat as you can right at the exhaust outlet so that there isn't a pressure increase slowing down flow.

Another way you might go about this is to minimize heat loss in all places except where you specifically want the heat to go. Insulate your exhaust and intake. If you want heat exchange from the exhaust to the intake, you don't want heat exchange anywhere else, so if you insulate the tubing, you can mitigate much of the heat loss, making the system more efficient than it would have been before, so your heat exchanger might have less of an impact on exhaust flow velocity.

Keep in mind, also, that you will need to periodically clean the heat exchange surfaces. If you don't, they will stop transferring heat. Lint is a great insulator.