recirculating exhaust smoke from stoves- this is not a 20th century idea, it's actually an 18th century idea. Ben Franklin tried it with fireplaces in the 1700's and was marginally successful. It does work to a degree, IF the stove or fireplace is burning quite briskly, to keep the chimney and circuit path hot, and draft pressure and velocity high. At lower burning levels, it doesn't work so well, leading to the smoke backing up into the room. Here's Franklin's patent idea, and he actually read up and copied this idea, from a previous one, so this has been around a long, long time- since the early 1600's. All a baseheater coal stove does, is take this principal and apply it to a free standing coal stove, and it does have drawbacks.
I have a relative with a coal/wood stove that has the exit pipe at a slight downward angle to the wall. That stove has the poorest draft I've ever seen on any stove in my life. He has good firewood burning performance, but lousy coal burning performance, the stove just doesn't have enough draft. The rule of thumb for flue pipes is minimum a few degrees upward angle over any horizontal run. A baseburner or Franklin stove makes the smoke go DOWN, which it inherently doens't want to do. If you use a recirculating type stove, best have a chimney with a LOT of draft. The last thing you want to do with one of these, is CLOSE THE FLUE PIPE DAMPER- now you're asking for trouble. It can then cool down and backdraft into the room.
here are the problems one may encounter with an antique stove or fireplace, using a recirculating design, once that smoke cools enough, the draft falls off and backdraft will occur, i.e. smoke into the room.http://en.wikipedia.org/wiki/Franklin_stove#Design
DesignThe height of the stove was about 30 inches tall with a box shape. The front side was open, except for a decorative panel in the upper part of the box. The back of the box was to be placed a few inches away from the flue, or chimney. On the bottom panel there were several holes to allow the smoke to escape; these were connected to the chimney. These panels were bolted together with iron screws through pre-cast ears. Inside there was a small thin rectangle prism that would force the smoke into the holes. The plates were all made from iron.
Franklin's stove sold poorly. The problem lay with the inverted siphon: the smoke had to pass through a cold flue (which was set in the floor) before the smoke could enter the chimney; consequently, the smoke cooled too much and the stove did not have a good draft. The inverted siphon would operate properly only if the fire burned constantly, so that the temperature in the flue was high enough to produce a draft.
Inverted siphons in fireplacesSome early experimenters reasoned that if a fire in a fireplace were connected by a U-shaped duct to the chimney, the hot gases ascending through the chimney would draw the fire's smoke and fumes first downwards through one leg of the U and then upwards through the other leg and the chimney. This was what Franklin called an "aerial syphon" or "syphon revers'd". This inverted siphon was used to draw the fire's hot fumes up the front and down the back of the Franklin stove's hollow baffle, in order to extract as much heat as possible from the fumes.
The earliest known example of such an inverted siphon was the 1618 fireplace of Franz Kessler. The fire burned in a ceramic box. Inside the box and behind the fire was a baffle. The baffle forced the fire's fumes to descend behind the baffle before exiting to the chimney. The intention was to extract as much heat as possible from the fumes by extending the path that the fumes had to follow before they reached the chimney.
The 1678 fireplace of Prince Rupert (1619–1682) also included an inverted siphon. Rupert placed a hanging iron door between the fire grate and the chimney. In order to exit through the chimney, the fire's fumes and smoke first had to descend below the edge of the door before rising through the chimney.
Another early example of an inverted siphon was a stove that was exhibited in 1686 at a fair in St. Germains, France. Its inventor, André Dalesme (1643–1727), called it a smokeless stove (furnus acapnos). The stove consisted of an iron bowl in which the fuel was burned. A pipe extended from the bowl's bottom and then upwards into a chimney. Shortly after starting a fire in the bowl, hot air would begin to rise through the pipe and then up the chimney; this created a downward draft through the bowl, which drew the fire and its fumes down into the bowl. Once the draft was initiated, it was self-sustaining as long as the fire burned. Dalesme's stove could burn wood, incense, and even "coal steept in cats-piss" yet produce very little smoke or smell. These results showed that fires could be used inside a room, without filling the house with smoke.
Franklin's stove contained a baffle directly behind the fire, which forced the fire's fumes to flow downward before they reached the chimney. This required a U-shaped duct in the floor behind the stove, so that the fumes could flow from the stove into the chimney. Thus Franklin's stove incorporated an inverted siphon.