Detailed information about Benjamin Franklin is given on this website. Today we will talk about Benjamin Franklin Stove and you can also read the Benjamin Franklin Short Biography
Benjamin Franklin Stove
The Franklin stove, invented by Benjamin Franklin in 1743, is a metal-lined fireplace with a hollow baffle and an inverted siphon to transfer heat. Designed to produce more heat and less smoke than open fireplaces, it gained popularity until David Rittenhouse improved it. Also known as a “circulating stove” or Pennsylvania fireplace, it is no longer used today.
Baffles in fireplaces
Baffles were used to increase heat transfer in ductwork, allowing more air to enter a room or fire’s fumes. Ducts were installed around a hearth, allowing cool air to enter the lower end of a duct, be heated by the hot walls, rise, and exit from the upper end. The longer the path, the more heat was transferred from the fire to the air, and the longer the duct through which fire fumes had to flow before reaching the chimney, the more heat was transferred from the fumes to the room’s air.
Franz Kessler’s 1618 publication, Holzsparkunst, introduced the use of baffles to extract more heat from fires and fumes. The stove featured five chambers, forcing fumes to snake through before entering the chimney. Kessler also documented an enclosed heating stove with a baffle behind the fire, extending the path of the fire’s fumes before reaching the chimney.
In 1624, French physician Louis Savot described a fireplace in the Louvre with ducts that circulated cool air under, behind, and above the fire. In 1713, Frenchman Nicolas Gauger published La Mécanique du Feu, presenting innovative designs for fireplaces. Gauger’s design involved hollow spaces surrounded by baffles, where cool air entered through lower openings, warmed around the baffles, and returned to the room through upper openings. Both Savot and Gauger contributed to the development of fireplaces.
Franklin’s stove featured a hollow baffle, a wide cast-iron box with two holes on its sides. The baffle heated air by the fire and fumes flowing over the box, allowing it to enter and exit the room. It also extended the path of the fire’s fumes before reaching the chimney, allowing more heat to be extracted. Similar to Gauger’s fireplace, Franklin’s baffle placed a duct near the fire, heating the room’s air via convection. This design served two functions in heating the stove.
Inverted siphons in fireplaces
Early experimenters believed that a U-shaped duct connected to a fireplace fire would draw smoke and fumes downwards through one leg of the U and upwards through the other leg and the chimney, creating an “aerial siphon” or “siphon reversed.” This inverted siphon was used to draw hot fumes up and down the back of a Franklin stove to extract maximum heat from the fumes.
The 1618 fireplace of Franz Kessler is the earliest known example of an inverted siphon. The fire was in a ceramic box with a baffle behind it, forcing the fumes to descend before exiting to the chimney. The aim was to extract maximum heat from the fumes.
Prince Rupert’s 1678 fireplace featured an inverted siphon and a hanging iron door between the fire grate and chimney. The fire’s fumes and smoke had to descend below the door’s edge before rising through the chimney.
André Dalesme, an inventor of the smokeless stove, demonstrated an early example of an inverted siphon at the Foire Saint-Germain in Paris in 1686. The stove consisted of an iron bowl and a pipe that extended into a chimney.
Hot air rose through the pipe and chimney, creating a downward draft that drew the fire and fumes down into the bowl. This self-sustaining draft was self-sustaining as long as the fire burned. Dalesme’s stove could burn wood, incense, and “coal steep in cats-piss” without producing much smoke or smell, demonstrating that fires could be used inside a room without causing smoke.
Franklin’s stove had a baffle behind the fire, directing fumes downward before reaching the chimney. This required a U-shaped duct in the floor, creating an inverted siphon, allowing fumes to flow from the stove into the chimney.
Franklin’s research and development
Jean Théophile Desaguliers translated Gauger’s book on innovative fireplace designs into English, introducing a new method of building chimneys to prevent smoking. Desaguliers also briefly described Gauger’s fireplaces in his book A Course in Experimental Philosophy. Franklin, inspired by Desaguliers’ work, developed his own stove designs that provided more heat with less smoke.
In 1742, Franklin designed a stove that implemented new scientific concepts about heat, based on Herman Boerhaave’s ideas. He supplied his equipment from William Branson, a local iron pioneer from Reading, PA. Franklin wanted his stoves to be available to everyone and eschew patents, leading to the first Franklin stoves being manufactured by Reading Furnaces owned by the local Van Leer family.
Two years later, Franklin wrote a pamphlet describing his design and how it operated to sell his product. Despite an offer from Deputy Governor George Thomas to patent his design, Franklin never patented any of his designs and inventions. As time progressed, the Franklin stove’s main use became to heat a room.
Many others improved on the Franklin stove design, but most American fireplaces are box-shaped, similar to the Franklin stove. The exception is the Rumford fireplace, developed by Benjamin Thompson.
Stove design
The stove was 30 inches tall and had a box shape with an open front and decorative panel. It was placed near the chimney and had holes for smoke escape. The panels were bolted together with iron screws through pre-cast ears. Inside, a small rectangular prism was used to force smoke into the holes. All plates were made from iron.
Franklin’s stove was unsuccessful due to an inverted siphon issue where the smoke had to pass through a cold flue before entering the chimney, causing excessive cooling and poor draft. The inverted siphon would function properly only when the fire burned constantly, ensuring a high flue temperature for draft production.
David Rittenhouse designed a later version of Franklin’s stove, which solved many issues and became popular. Franklin’s fame outpaced Rittenhouse’s, so history remembers the Franklin Stove. The smaller Latrobe stove, patented in 1846, became popular.
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