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Cold Mechanical Steam Compression Dryer

Like MSC, but lower pressure
  [vote for,

For those of you who haven't heard of mechanical steam compression clothesdryers, they work like this:

First, the tumbler and the clothes are heated up to 100C; the steam that's initially produced displaced all of the air, resulting in a steam-only atmosphere inside the machine. Some of that steam is taken out, compressed (raising it's temperature), passed through the inside of the condenser; the resulting liquid water exits the condenser via either a float valve or a pressure release valve, and is discarded down a drain. Some of the steam from the tumbler is pulled out via a blower, sent around the outside of the condenser (which superheats it), then blown back into the tumbler.

Such machines are both energy efficient and fast at drying clothing, but have one really big downside: They operate at a range of 100C - 120C, and are not suitable for heat sensitive clothing types.

I propose modifying this existing technology, by putting the components into a vacuum chamber, and adding a gas/liquid separator, an additional compressor, and a pump.

When the system is initially turned on, air is pulled from the dryer by the primary compressor, passed through the separator, then the secondary condenser, then vented.

A float valve in the gas/liquid separator will, when liquid is present, turn off the secondary condenser and turn on the condensate pump; this pump pulls water out of the separator and discards it.

As with a regular MSC clothes dryer, a blower pulls gas (either air or steam, depending on the drying phase) out of the tumbler, past the condenser, and back into the tumbler.

In addition, there is a thermocouple, with one end inside of the gas/liquid separator, and the other on the outside of the machine. If the temperature in the separator is below the temperature of the room, the secondary compressor is turned off, even when there's no liquid in the separator. This keeps the system's overall temperature close to ambient, which maximizes efficiency. This also keeps system temperatures well above the freeze-drying range.

As a result, we now have a clothes dryer which is just as fast and efficient as MSC, but which operates at near- ambient temperatures, and should be suitable for all types of clothing.

Caution: If you accidentally put a pen in the dryer with your clothes, it's guaranteed to explode and make you unhappy, as the pressure drop will make the ink boil and expand out of the pen.

Optional: A feature to run the system with the tumbler not spinning, so it can be used to make homemade dried foods. Use of a battery powered fan for circulation is suggested. Cleaning or replacing the filter when switching from making dried food to drying clothes is strongly recommended (unless of course you *want* to smell like jerky).

goldbb, Jul 15 2011

Previous posting Combo_20Washer_20and_20Freeze-Dryer
You have described something very similar to "freeze drying". And a washing machine especially a front-loader, has the seals and most of the toughness needed to stand up to air pressure when doing vacuum-drying. [Vernon, Jul 15 2011]

Degreaser dip Degreaser_20dip
With acetone! Would probably also work to dry clothes. [bungston, Jul 15 2011]


       This device would be useful for those who want to dry their clothes / make beef jerky without detection by unmanned aerial drones with infrared cameras. Bun for consideration of people who want to smell like jerky.
bungston, Jul 15 2011

       Could use ether rather than water in the wash - has a lower boiling point so a normal machine could opperate at the lower temp:O)
saedi, Jul 15 2011

       /ether/ see Degreaser dip, linked.
bungston, Jul 15 2011

       Vernon, thanks, your idea was actually part of the inspiration for this one. My apologies for forgetting to link to it.   

       However, in my idea, the "freeze" aspect of "freeze drying" never occurs. The majority of the drying is accomplished by blowing superheated steam through the clothes.   

       Bungston, dipping clothing in acetone would certainly remove the water -- but that isn't really drying, since the acetone is of course a liquid, and thus the clothes are still wet (just with acetone instead of water). The acetone would need to be removed from the clothes after doing that.   

       Conveniently enough, my idea would not only remove the acetone from the clothes, but recover the vast majority of the acetone as a liquid.   

       Come to think of it, this idea would be just as fast and energy efficient for the final stage of drying for dry- cleaning, as it is for the drying of water-dampened garments. The drying stage of a modern dry-cleaner is done by a the same mechanism as a "heat pump dryer," which is as efficient as (but half as fast as) mechanical steam compression drying.
goldbb, Jul 15 2011

       I just thought of a way to make a dryer using this idea slightly cheaper to construct: instead of having two compressors, have one.   

       When there is no liquid in the gas/liquid separator, the compressor will *either* move gas from the dryer into the condenser, *or* move gas from the separator into the atmosphere, depending on whether the temperature in the separator is below or above the ambient temp.   

       The system would be the same as I first described in all other ways.   

       Naturally, it would take a little longer than the original version to get one's clothes dry, but I don't believe the increase in running time would be particularly extreme.
goldbb, Jul 15 2011

       Super critical co2 would be my choice for washing clothes. Any liquid co2 left after the spin down would just boil away. Of course that means the feeling of using a fresh hot towel from the dryer will be lost to future generations
duroncrush, Jul 21 2011


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