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stevehull · 09-16-13, 03:28 PM

Gascort,

Great idea using counter current concept, but here is a critical problem - condensation . . . .

Years ago (~1980), I saw the same paradox; all that heat going out the wall when it could be used to heat the house (I was living in East Lansing Michigan). So, I rigged up a serpentine set of aluminum pipes (exhaust dryer vent material) with two 90 degree elbows to make a 180 degree turn. One end connected to the electric dryer vent outlet and the other went out to the wall outlet.

I must have had five or six of the exchange tubes with maybe a dozen 180 degree turns. All mounted on the wall horizontally with stand offs above the washer dryer. The total length of pipe was perhaps 50 feet. It looked great, so pretty and shiny and I was SO proud of my skills and ability to save $ . . .

I blew air from the house air handler system across the wall mounted aluminum heat exchanger and it worked GREAT!! The amount of heat dissipated was superb with about a 30-40 F decrease in the temp measured at the dryer outlet part of the exchange tube to where it exited the wall.

But then reality kicked in. Despite being careful to change the lint filter, my beautiful shiny heat exchanger began to accumulate lint. And yes, the lint stuck to the insides of the aluminum pipe and the heat performance began to degrade terribly

. Then one day, it began leaking water and that dripped on a clean stack of dried clothes. New baby in the house and Momma was NOT happy

.

Turns out, the temperature humidity relationship of a dryer is rather strict. The air going out is quite saturated with water vapor for that temperature. Decrease the temp and the moisture in that dryer air WILL condense out.

The year before I had put a "heat reclaimer" on the woodstove stack and it accumulated tremendous amounts of creosote (for exactly the same reasons).

So, I have given up on reclaiming dryer heat and instead have put washer/dryer in a sealed room with an outside air vent (for makeup air). I used an outside door for the room entry with good neoprene gaskets and a good sweep seal so the door sealed quite well. The make up air vent (6 inches) comes down from the attic and I put a filter over the open end in the attic. This works REALLY well.

Nobody sees it but I remain proud of the savings nevertheless

.

Steve

09-16-13, 03:28 PM	#95
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	Gascort, Great idea using counter current concept, but here is a critical problem - condensation . . . . Years ago (~1980), I saw the same paradox; all that heat going out the wall when it could be used to heat the house (I was living in East Lansing Michigan). So, I rigged up a serpentine set of aluminum pipes (exhaust dryer vent material) with two 90 degree elbows to make a 180 degree turn. One end connected to the electric dryer vent outlet and the other went out to the wall outlet. I must have had five or six of the exchange tubes with maybe a dozen 180 degree turns. All mounted on the wall horizontally with stand offs above the washer dryer. The total length of pipe was perhaps 50 feet. It looked great, so pretty and shiny and I was SO proud of my skills and ability to save $ . . . I blew air from the house air handler system across the wall mounted aluminum heat exchanger and it worked GREAT!! The amount of heat dissipated was superb with about a 30-40 F decrease in the temp measured at the dryer outlet part of the exchange tube to where it exited the wall. But then reality kicked in. Despite being careful to change the lint filter, my beautiful shiny heat exchanger began to accumulate lint. And yes, the lint stuck to the insides of the aluminum pipe and the heat performance began to degrade terribly . Then one day, it began leaking water and that dripped on a clean stack of dried clothes. New baby in the house and Momma was NOT happy . Turns out, the temperature humidity relationship of a dryer is rather strict. The air going out is quite saturated with water vapor for that temperature. Decrease the temp and the moisture in that dryer air WILL condense out. The year before I had put a "heat reclaimer" on the woodstove stack and it accumulated tremendous amounts of creosote (for exactly the same reasons). So, I have given up on reclaiming dryer heat and instead have put washer/dryer in a sealed room with an outside air vent (for makeup air). I used an outside door for the room entry with good neoprene gaskets and a good sweep seal so the door sealed quite well. The make up air vent (6 inches) comes down from the attic and I put a filter over the open end in the attic. This works REALLY well. Nobody sees it but I remain proud of the savings nevertheless . Steve __________________ consulting on geothermal heating/cooling & rational energy use since 1990 Last edited by stevehull; 09-16-13 at 03:30 PM..