Thread Number: 11335
One of life's unanswered questions:
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Post# 203672   4/13/2007 at 12:21 (6,194 days old) by marukap (St. Louis)        

I am fascinated and PUZZLED by how vintage, and for that matter new-fangled, condensing clothes dryers work. Do any of you gurus have photos or schematics of the innards of these mystery machines?

Thanks,

Martin Kaplan





Post# 203740 , Reply# 1   4/13/2007 at 19:12 (6,194 days old) by thor (Buenos Aires)        
Condensing dryers

Martin, the modern condensing dryers operate with two air circuits: a closed air circuit which circulates inside the dryer (which is electrically heated and circulated through the wet clothes) and an open air circuit which takes air from the room, slightly cools the first air in a heat exchanger, and then discharges it back to the room, slightly heated. As the closed air circuit heats up at some point it saturates to 100 % humidity (with the moisture taken away from the clothes being dryed) and then it is very slightly cooled in a heat exchanger with room air (these air circuits actually don't mix!), and as the closed circuit air is cooled part of the moisture condenses. Condensed water is then stored in a container which has to be emptied after so many cycles, or flushed away with a small water pumped through a plastic pipe. Theoretically there is a very small amount of heat given into the room, but then, this is "theoretically".

Older dryers had a cold water connection to cool the closed air circuit in a heat exchanger. These units were prone to extensive service calls.

I hope this clears your doubt.

Emilio


Post# 203803 , Reply# 2   4/13/2007 at 22:48 (6,194 days old) by marukap (St. Louis)        
Clarity at last

Dear Emilio:

Thank you very much for a most informative description.

Martin


Post# 203858 , Reply# 3   4/14/2007 at 08:03 (6,194 days old) by thor (Buenos Aires)        
Third type

You are welcome Martin, I'm actually quite surprised you could understand my explanation, LOL!

I forgot to add there is a third type of condenser dryers, which actually use a cooling system to condense moisture from the closed air circuit, just like in a frost free refrigerator. Air is heated without an electric resistance, since the cooling system actually works as a "heat pump". These dryers are manufactured by AEG from Germany, and they are rather expensive, but is the only kind of electric dryer with an "A" classification for efficiency. I've heard they are excellent dryers!

Please feel free to ask for the translation of any part of the specifications, I can manage some German also. Emilio

Emilio


Post# 203859 , Reply# 4   4/14/2007 at 08:05 (6,194 days old) by thor (Buenos Aires)        
Forgot to add the URL to the AEG site

Here's a link to the AEG condensing dryer with heat pump!

CLICK HERE TO GO TO thor's LINK


Post# 203860 , Reply# 5   4/14/2007 at 08:08 (6,194 days old) by thor (Buenos Aires)        
1200 W

If you look at the bottom of the technical specifications you will find the dryer just consumes 1200W! No wonder it has an "A" classification.

Emilio


Post# 203862 , Reply# 6   4/14/2007 at 08:15 (6,194 days old) by thor (Buenos Aires)        
In English!

Found the same specifications in English!

CLICK HERE TO GO TO thor's LINK


Post# 203883 , Reply# 7   4/14/2007 at 11:54 (6,193 days old) by marukap (St. Louis)        

I wonder if we could jury-rig our own "heat-pump" and more-or-less high efficiency condensing dryer by creating a closed air loop between the exhaust and the intake on a conventional machine that is made to pass through a room dehumidifier. The dryer would be set on a no-heat cycle. . . .We'll show those German engineers a thing or two!

Marty


Post# 203885 , Reply# 8   4/14/2007 at 12:03 (6,193 days old) by neptunebob (Pittsburgh, PA)        

neptunebob's profile picture
The problem is probably dealing with the lint. All three of my sisters have dehumifiers in their basement laundry rooms and all get clogged with lint and have to be vacuummed. I don't mean to be a wet blanket (pun intended) but I don't think people would stand for that. As it is, some people don't even know what brand their dryer is because "It's no fun to use so I try not to look at it".

Post# 203929 , Reply# 9   4/14/2007 at 16:09 (6,193 days old) by accapp ()        

The Equator combo W/D uses cold water from the washer's supply hose to cool down the condenser area. Wastes a lot of water but uses less electricity. There are other condensing dryers that use cold water as well.

Post# 203941 , Reply# 10   4/14/2007 at 17:58 (6,193 days old) by launderess (Quiet Please, There´s a Lady on Stage)        

launderess's profile picture
Remember when I was back at school, our Home Economics lab had a water cooler full sized dryer. Cannot remember the brand name, but one day when helping the home ec instructor load the dryer she complained about having to use it even when there was a water shortage.

Really is a shame that an effective full sized condenser dryer is not around. But then again every system of drying laundry which does not vent the exhaust has to over come the "lint" problem.

Many people think because they cannot "see" lint dust coming out of a dryer vent it is not there, which simply is not true. This especially applies to those who use those indoor water bucket vent things. Lint is a fine dust that is quite difficult to filter, and a pair of nylons wrapped over the aforementioned bucket is not going to do the job. Over time that lint goes every where and gets on and into every thing, especially electronic equipment and appliances that use any sort of fan/motor such as computers.

This fine lint is also combustible, VERY combustible which is the reason for all those warnings about keeping dryer lint filters and vent runs clean. Commercial laundries/laundromats often have such fires if the owners are not doing routine exhaust cleaning.

L.


Post# 204014 , Reply# 11   4/14/2007 at 22:09 (6,193 days old) by thor (Buenos Aires)        

L.

Condensing dryers do not vent the drying air into the room. The dyring air circulates around a closed loop, first heated through an electrical resistance, then blown across the drum, then through the lint filter, then sucked by the fan and blown back to the resistance, and so forth. Lint is not discharged into the room. The "cooling" air taken from the room and discharged back to the room actually never gets in contact with the air inside the dryer, which actually contains the lint.
Emilio


Post# 204119 , Reply# 12   4/15/2007 at 08:21 (6,193 days old) by gadgetgary (Bristol,CT)        
*WAVES* Greetings from Toggleswitch

gadgetgary's profile picture
What's intersting about this is that the heat produducng "coil" of the heat-pump heats the drum air loop. It would make sense to cool the incoming room air that is used to cool the condenser with the other side (coil) of the HP. The bigger the tenperature difference between the air to be dried and the condensing air-stream means greater effectiveness!

A win-win situation!

Posting fom GadgetGary's log-in. Mine is not cooperating today.


Post# 204152 , Reply# 13   4/15/2007 at 12:02 (6,192 days old) by thor (Buenos Aires)        

Toggle, just a product of my imagination, but maybe the AEG heat pump dryer doesn't use any room air at all!

I imagine the evaporator (cooling) coil of the heat pump could be a part of the closed air loop. In this setup the evaporator coil would first cool and dehumidify the loop air, which would be immediately heated back by the condenser coil of the heat pump, located immediately after the first coil. In a refrigeration cycle (or heat pump cycle) more heat than cool is generated, so the loop air would actually tend to "heat up" as it dries up, an ideal situation! But then, once again, this is just how I "imagined" the system might work.

Emilio



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