Half a croissant, on a plate, with a sign in front of it saying '50c'
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Dehumidification Engine

Internal Adsorption Engine
  [vote for,

At first glance, this device resembles an internal combustion engine -- it has cylinders, pistons, a crankshaft and connecting rods, cylinder heads, poppet valves, and intake and exhaust manifolds.

At second glance, one notices that there are four manifolds: An interior intake manifold, an interior exhaust manifold, an exterior intake manifold, and an exterior exhaust manifold. Naturally, each cylinder head has four separately controlled valves or sets of valves, instead of the usual two of an ICE.

The interior of each of the engine's pistons has a block of water adsorbing material attached to it -- probably a block of silica gel beads.

Each piston moves up and down through a six stroke cycle.

At the beginning of the first stroke, the piston is at TDC, and all valves are closed. The interior intake valve opens, and the piston moves downward, causing air from the room being dehumidified to move in to the cylinder.

At the beginning of the second stroke, the piston is at BDC, and the intake valve closes. As the piston moves up, the air is compressed. As air is compressed, latent heat (humidity) is forced into the adsorbent, and sensible heat is conducted into the piston, cylinder walls, and cylinder head.

During the third stroke, the piston moves partway down with all valves still closed. Because both heat and mass have been transferred out of the air, it reach will atmospheric pressure *before* BDC. When this happens, the interior exhaust valve opens. The piston then continues to BDC.

For the fourth stroke, the piston rises with the interior exhaust valve open, sending the cooled, dehumidified air back into the room from which it came.

At the beginning of the fifth stroke, the interior exhaust valve closes, and the exterior intake valve opens.

The piston descends partway, allowing some air from outside the building into the cylinder, and then the valve closes.

As the piston continues to descend, the pressure in the cylinder drops below atmospheric pressure, and moisture is desorbed by the adsorbent, and heat is conducted from the piston, cylinder walls, and cylinder head, into the cool, low pressure air.

For the sixth stroke, the piston rises until the air has been compressed to atmospheric pressure, and then the exterior exhaust valve opens. The piston continues to rise, expelling the warm, humid air to the exterior of the building. Then, at TDC, the valve closes.

After the sixth stroke, the first stroke repeats.

goldbb, Jul 18 2012


       Although this idea focuses on removing humidity from a room or building, it could be adapted to producing concentrated oxygen, simply by using an alternative adsorbent.
goldbb, Jul 18 2012

       Depending on the results from testing, it might be desirable to use an eight stroke cycle, where the seventh and either strokes are identical to the fifth and sixth strokes -- this would allow a larger volume of air per cycle to be used for the purpose of removal of heat and humidity.
goldbb, Jul 18 2012

       So, on hot, humid days you end up with a massive mound of used, hydrated silica gel (or sodium polyacrylate) sitting in your backyard?   

       Where does the energy to run this marvellous device originate?
UnaBubba, Jul 18 2012

       I'm guessing it would work -- barely -- if it's all light plastic. You won't get any energy out but I think it will move.
Voice, Jul 19 2012

       The goldfish moves.
UnaBubba, Jul 19 2012

       // mound of ... Silica Gel //   

       On careful reading, we deduce that the third part of the cycle is intended to regenerate the silica gel.   

       Thermodynamically it shoud just about work. Yes, it absorbs rather than generates energy.   

       The killer is probably that it needs to operate at very low cyclic speeds to allow all the themal transfers to occur. An ICE doesn't rely on thermal transfer between the working fluid and the structure of the engine; this sounds more like a reverse Newcomen engine.
8th of 7, Jul 19 2012

       A six-stroke steam-_injection_ ICE has already been built, pressurizing the moisture generated by the combustion to both power the additional rotation and to clean the cylinder. That makes sense, and it works.   

       This idea makes sense in an utterly impractical sort of way, and I'm not all that sure it would actually run. The air compression with no power gain on the sixth stroke might be enough to stall the engine at idle--unless the third rotation is cut out at idle and only occurs at running speed.   

       I can't recall off the top of my head the name of the guy who built the 'six-stroke steam-assisted'; he's a famous race engine designer from the Southwest US. He once converted a 6-cylinder Mercedes engine into a two-stroke "just to hear what it would sound like." Anyone know who I'm talking about?
Alterother, Jul 19 2012

       Bruce Crower of Crower Cams.
FlyingToaster, Jul 20 2012

       Voice -- it's not supposed to move by itself or generate mechanical power; it is externally powered by an electric motor (or other prime mover), and consumes mechanical power.   

       8/7 -- In an ICE, thermal transfer between the working fluid is and the structure of the engine, while generally undesirable, is the source of the vast majority of the heat which is dissipated through the engine's radiator. This, in turn, is roughly equal to the amount of mechanical power that the engine produces. Since it occurs in such high quantities in an ICE, it ought to occur in reasonable quantities in this invention.   

       Alterother -- this engine isn't designed to run by itself, but needs to be spun by an outside source of mechanical power. It's not a prime mover. I call it an engine because it looks much like one, and has many parts in common.   

       And the guy who's six-stroke water-injection steam- expansion engine got printed in Popular Mechanics, and who converted a Mercedes five-cylinder engine to a two- stroke was Bruce Crower.
goldbb, Jul 20 2012

       I get it now. I misunderstood the introduction. Thank you both, as well, that's the man and the article I was thinking of.
Alterother, Jul 20 2012

       Thanks heavens you got this idea, goldbb! I am developing a mechanism for my rotary engine using Oxyfuel combustion process for two years already. But there's one big hurdle though that I am uncertain--Do Oxygen chemical adsorbents operating at 800 deg. Centigrade fast enough to operate in 10,000 cycles/minute?   

       It's ideal for me to go to Chemistry literature regarding Oxydation-Reduction processes and ideal compounds involved, but my schedule might even get tighter. I am bogged down with way too much Mechanical Engineering literature at hand. It's definitely practical for me to solicit your expert opinions regarding this matter.   

       Any suggestions?
rotary, Sep 04 2012


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