Wade Smith

Hi all, just a thought/additional question on why a Rocket Heater/J-Tube produces far more BTU's than what normal wood charts say they do. I remember researching Gasifiers some time ago and someplace between mental wandering and mowing grass, I remembered that back around 1900, the first vehicle was developed to run on "wood gas or commonly known as syn gas". After doing some rough calculations and quick internet search's, I found a quick and dirty reference to how much "wood/syn gas" is in 1 lb of wood. 1lb of wood at 15% moisture content produces 35 cubic feet of gas or 4,900 BTU heat from burning the gas direct ( http://wiki.gekgasifier.com/w/page/6123680/Biomass%20to%20Woodgas%20to%20BTU%20to%20HP%20to%20KW%20to%20MPG%20conversion%20rules). Could this be the missing component/explanation as to why the Rocket Heaters/J-Tube heat output numbers never match the BTU ratings of burning wood?

Hi all, actually Cindy, on page 4, it shows the Purple trace just over 15K BTU if complete combustion is achieved (all carbon and gases) with the Red trace being the more familiar HHV numbers. The only reason I somewhat believe the higher number is that I did build a "metal rocket stove" using an old 100 lb propane tank for a body, 5x5x1/4 wall tube for the J-Tube, Vermiculite (approx 2 1/4 cubic ft) for the insulation tube and a 1 1/2" gap between the insulation tube and the outer shell and a 4" exhaust.
With that said, I have a 2,000 sq. ft. house, the temp outside was 0 F degrees, wind chill was -10 F and the temp in my house was at 58 F when I got home from work. Within 2 1/2 hours of starting the "metal rocket heater" I had the house (bedrooms, bath's, and living room) at 72 degree's F with the 18'x22' great room that the Heater was in running at 85 F. The biggest challenge I had was getting the heat out of the 100 lb shell before going out to exhaust (average exhaust temps ran from 140F to 165F). I ran fans across the steel surface to aid in extracting heat from the shell surface.
That is where the numbers go NUTS.... If I ran the nominal 5800 BTU's per pound of wood calculation, I would have to shove close to 21 lbs of wood per hour into a 4.5" square opening to maintain a 120,000~ish BTU rating just to maintain the 0F outside to 72F inside ratio. If it helps, I was burning Beech, somewhere between 5-8 lbs and hour, zero smoke from the stack, a continuous heavy drip of clear water from the exhaust, and a more white~ish colored than yellow sideways flame was present.
So that is the current dilemma of trying to figure out what the "true" combustion numbers are for burning wood in a Rocket Heater/J-Tube. I am just as much a skeptic as everyone else on efficiency numbers and can only correlate the numbers I witnessed to what's available and nothing seems to add up until I ran the numbers with the EPA study for the "complete combustion" trace in purple on page 4.

Hi everyone,
I am a fairly new member to the Rocket Heater/J-Tube construction (I have built 2 Rocket Heaters in 4 months) and have a question about the BTU’s per pound of wood being burned in a Rocket Heater. Most all of the charts available on the internet put wood at an average of 8,600 BTU’s per pound of wood for energy output. When I was researching how much heat was being generated by Rocket Heaters for so little fuel being used, the amount of heat, pounds of wood, and total BTU’s did not make any sense what so ever. After doing some MAJOR digging, I ran across a paper that was funded by the EPA and published by Intertek( http://www.epa.gov/burnwise/workshop2011/WoodCombustion-Curkeet.pdf ).
The question I have is what BTU numbers are really correct for burning wood in a Rocket Heater/J-Tube constructed appliance? The EPA funded study says that if you achieve 100% combustion (carbon and gases from pryolysis) you will achieve just over 15,000 BTU’s per pound of wood. If anyone could give me a better source of information, I would appreciate it.