Half a croissant, on a plate, with a sign in front of it saying '50c'
h a l f b a k e r y
Assume a hemispherical cow.

idea: add, search, annotate, link, view, overview, recent, by name, random

meta: news, help, about, links, report a problem

account: browse anonymously, or get an account and write.

user:
pass:
register,


                                         

Desiccant Clothesdryer

More energy efficient dehumidfying clothesdryer
 
(+3, -3)
  [vote for,
against]

Circulate air between the tumbler full of clothes and a liquid desiccant air handler.

At the same time, circulate the liquid desiccant between the air handler and a vapor compression distiller.

The liquid desiccant would be something cheap and safe, such as calcium chloride dissolved in water.

goldbb, Jul 28 2009

Munters desiccant dehumidifiers http://www.munters....nditioning-Systems/
Proven technology. [8th of 7, Jul 29 2009]

How Conventional Clothesdryers Work http://home.howstuffworks.com/dryer.htm
[goldbb, Jul 30 2009]

Munter's actual core technology http://www.munters....Technologies/Rotor/
[goldbb, Jul 30 2009]

[link]






       umm isn't "something dissolved in water" by definition pretty well used up as far as dessicating abilities is concerned ?
FlyingToaster, Jul 29 2009
  

       wouldn't you have to use about the same amount of energy to "dry" or reactivate the dessicant as you would have used to just dry the clothes with heat and ambient air? Plus all the losses. I don't see how this could be more energy efficient unless you know that it's more efficient to dry dessicant than clothes.
JackyD, Jul 29 2009
  

       Using a conventional (compressor) dehumidifier in a drying room has a lot of benefits; the clothes dry faster, the humidity is lower (no condensation) and the by-product is a useful amount of distilled water. The small (300w) energy input into the space from the dehumidifier helps dry the clothes faster. Overall, it's much more energy-efficient than tumble drying.   

       We submit that this is Baked.
8th of 7, Jul 29 2009
  

       I seem to remember something called "dry-cleaning". Maybe it is on the wane in developed countries. It was only quite recently that we scrapped polar molecules with high volatility, like Carbon Tet. Because they are lethal, which was not as much of a concern as clean linen was, in the old days.   

       In fact, if I remember correctly, this idea was the carbon tet methodology, now continued with other, less lethal, chemicals.   

       [marked-for-deletion] widely known to exist. And if you don't widely know it, I suggest you subscribe to the "Don't use that with which you are unfamiliar with the inner workings of" Day.
4whom, Jul 29 2009
  

       Any method of clothes drying that does not take advantage, in a direct way, of the essentially free dry air found in most locations gets boned by me.
WcW, Jul 29 2009
  

       //umm isn't "something dissolved in water" by definition pretty well used up as far as dessicating abilities is concerned ?//   

       No, it isn't.
ldischler, Jul 29 2009
  

       For those who say it is baked, do you have a link to a desiccant tumble dryer?
ldischler, Jul 29 2009
  

       Yes, we do. <link>
8th of 7, Jul 29 2009
  

       I'm looking at the link. Where do you put the clothes in?
ldischler, Jul 29 2009
  

       In the building underneath the air handler.
8th of 7, Jul 29 2009
  

       Nope. Not baked, and certainly not widely known to exist.
ldischler, Jul 30 2009
  

       FT... in a word, no :).   

       In many more words...   

       First, one needs to know how/why evaporation to air and condensation from air occur under normal circumstances.   

       Water at atmosphereric pressure boils/condenses at 100C. At lower pressures, it will boil at lower pressures.   

       At the surface between water and air, the water percieves the pressure on it to consist soley of the partial pressure of the water vapor in the air.   

       If the partial pressure of water vapor in air is low (aka low humidity), the water molecules at the liquid's surface think of the overall pressure as being low, which means that the boiling point of those surface water molecules is low... and if the surface water's boiling point is below their actual temperature, they will boil/evaporate.   

       Condensation from water from humid air into liquid water is the same, but with a high partial pressure of water vapor in air (high humidity) resulting in a surface boiling temperature higher than the air's actual temperature, which results in water vapor from the air condensing into the liquid water.   

       If a salt is added to the liquid water, it's boiling point is raised... if the boiling point of the salted water is above the boiling point determined by the partial pressure of water in air, then water vapor from the air will condense/be absorbed by the salted water.   

       Desiccants are salts which raise water's boiling point a lot. Consequently, they hugely lower the temperature at which water vapor near the desiccant's surface will condense.   

       JackyD, a vapor recompression distiller is a hugely efficient device, with respect to the heat that's added to it -- typically 2% of the heat needed for boiling comes from combustion of fuel, and 98% of the heat needed for boiling comes from the compressed steam.   

       And since the same air is continuously circulated between clothes and desiccant, none of the heat is lost to the environment, except that which escapes through the thermal insulation.   

       On the other hand, in a conventional clothes dryer, air is taken from the environment, heated, and passed through the clothes. A small fraction of that heat is absorbed into the water in the clothes, creating steam, and the hot humid air is then vented to the atmosphere.   

       I would *not* call that energy efficient.   

       Furthermore, the fresh air from the atmosphere has a certain amount of humidity in it. Heating the air lowers the relative humidity some, but not by as much as a desiccant can.   

       So not only does a regular clothesdryer throw away most of the heat it creates, the air it's blowing on the clothes is more humid than the air a dehumidifying dryer is blowing on the clothes.
goldbb, Jul 30 2009
  

       WcW... How about the following alternative version: the (modified) machine has an air intake and exhaust. Temperature and humidity sensors in the intake, exhaust, and interior, feed data to a computer. The computer then makes a decision, based on which costs less:   

       Either it circulate the (moister but hotter) air that's passed through the clothes to the desiccant, as per my original idea, or whether it will cost less to take in fresh (dryer but cooler) air from outside, and pass *it* through the desiccant (which will dry it further, and warm it).   

       At certain phases in the cycle, one or the other will be more cost effective. Near the beginning of the drying cycle, when the clothes are very wet, drying fresh air will probably consume the least energy per gram of water evaporated from the clothes. Near the end of the cycle, when the clothes are nearly dry (almost as dry as the atmosphere, and certainly warmer), it may be more cost effective to recirculated the air.
goldbb, Jul 30 2009
  

       8/7, The core technology of the company you linked to, is nothing fancier than a rotary regenerative heat exchanger, with a moisture adsorbing coating. Hot air is blow through it to dry it, and sent up the chimney. Not what I'd call efficient.
goldbb, Jul 30 2009
  

       8/7, Munters dehumidifier is nothing more than a rotor-type regenerative heat exchanger, with a hydroscopic coating.   

       Humid air to be dehumidified is blown through one portion of the rotor, and water is adsorbed from the air into the surface coating.   

       Fresh air from outside the building is heated, blown through the other portion of the rotor, where it causes the water to be desorbed, and then the hot humid air is vented (discarded) to the atmosphere.   

       This is almost identical to how a conventional clothesdryer works, and is just as inefficient.
goldbb, Jul 30 2009
  

       I've thought about this a bit myself, and perhaps it would work better if you had a solar dryer for the desiccant which could dry it at leisure, while the clothes dryer is not in operation.   

       The setup would have to be something like air is cycled through the dryer, then desiccant, and then to the roof of the building where the desiccant loses some water to evaporation.   

       I'm not sure how well liquid desiccants work, but there could be a desiccant slurry transport conveyor belt.   

       While this would be a very indirect way of line-drying your clothes, it would be less of a pain and definitely more energy efficient than a conventional dryer.   

       Freeze-dried bun.
cowtamer, Aug 01 2009
  

       goldbb, i liked the description of the dynamics of water condensation/evaporation. But even in light of that, I'm still not understanding how you get the water out of the dessicant. How does a vapor compression distiller work?
JackyD, Aug 14 2009
  
      
[annotate]
  


 

back: main index

business  computer  culture  fashion  food  halfbakery  home  other  product  public  science  sport  vehicle