One of life's unanswered questions:
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thor
Well-known member
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
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
thor
Well-known member
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
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
thor
Well-known member
Forgot to add the URL to the AEG site
Here's a link to the AEG condensing dryer with heat pump!
Here's a link to the AEG condensing dryer with heat pump!
thor
Well-known member
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
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
thor
Well-known member
In English!
Found the same specifications in English!
Found the same specifications in English!
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
Marty
neptunebob
Well-known member
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".
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.
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.
thor
Well-known member
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
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
*WAVES* Greetings from Toggleswitch
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.
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.
thor
Well-known member
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
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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