Jetstream Furnace - Wood-burning Water Furnaces, Boilers and Melters

Wood-burning Water Furnaces, Boilers and Melters

The furnace used a forced and induced draft fan to draw combustion air and exhaust gases through the combustion chamber at 1/3 of the speed of sound (100 m/s+). The wood was loaded into a vertical tube which passed through the water jacket into a refractory lined combustion chamber. In this chamber the burning took place and was limited to the ends of the logs. The water jacket prevented the upper parts of the logs from burning so they would gravity feed as the log was consumed.

The products of combustion left the chamber and passed through a narrow ceramic neck which reached temperatures of 2000 degrees F where the gases and tars released by the wood completed their burning. The products then passed through a refractory lined ash chamber which slowed the flow and let ash settle out. From here the hot gases travelled up through the boiler tubes which pass through the water jacket. Turbulators in the tubes improve heat transfer to the water jacket.

All this resulted in total efficiencies as high as 85% but more commonly 75-80% and allowed partly dry unsplit wood to be burned just as effectively and cleanly. The particulate production was 100 times less than airtight stoves of the 1970s and 1980s and was less than representative oil fired furnaces. The Jetstream produced approximately 0.1 grams/hours of soot while EPA certified woodstoves produce up to 7.2 grams per hour. The high combustion chamber velocities do result in fine particulate flyash being ejected from the stack.

The other aspect of Dr. Hill's design was the use of water storage. The furnace only operated at one setting, wide-open burn. A full load of hardwood, approximately 40 lbs would be consumed in four hours and the heat released was stored in water tanks for use through the day.

The Hampton Industries model was designed to produce 120,000 BTU (130,000 kJ).

A Hampton Jetstream Mk II which was set to be the next model offered by Hampton Industries existed in prototype form. It was an upsized version of the unit offered for sale. The only component changed was the diameter of the burning chamber. This was enlarged within the standard casting. The prototype shares many of the design improvements seen in the Kerr Jetstream.

The Tempest was produced by Dumont Industries of Monmouth, ME, USA and is very similar to the Jetstream.

The patent for this device, termed a WoodFired Quick Recovery Water Heater, number 4583495, issued April 22, 1986, is assigned to the Board of Trustees of the University of Maine. There is no current production using the design of this patent. (January, 2008)