![]() put a barrel on it the flame path is a little further down the heat riser then put the ducting in the thermal mass with the general couple corners that lowers the flame path a bit further. What this means is you build a core that roars and the flame path is near the top of the heat riser. in order to burn up most of the smoke you need it to be in the flame path for a period of time you need the gasses to mix and you need to have ignition temp. this catches lots of folks who want to modify the stove. your fire slows down, an essential thing to consider is time, temp and turbulence. You put drag on the exhaust you put back pressure on the J tube. the J tube part is only a piece of the whole When the barrel/bell goes on things change then when the thermal mass goes on things change again. If you have a 4" exhaust versus an 8" exhaust, the main variable effected is the pressure at that point in the flow.īreaking the stove down into its individual sections and tackling each separately will help you to maximize the rocket effect while maximizing the dollars in your wallet.Īctually your rocket stove should be considered as a system. This section of pipe also can be any size and will not have an effect on the intake. would be the exhaust where it finally leaves the building. would be the Heat Bench where we extract even more heat and store it like a capacitor stores electricity for release. not shown would be the barrel which is radiating heat into the room and cooling the air. This variable strongly effects the rocket effect. This is where the size should be as large as you can make it. is the Heat Riser where we are taking advantage of the heat expansion of air. The greater the temperature is in this section the greater the rocket effect. I used equations to prove this as well as tested it. According to the Bernoulli Principle, as the pressure decreases(smaller opening), the speed of the fluid, in our case air, increases. This is where the size does not have to equal the heat riser. When designing your Rocket Stove each section should be considered separately. Thanks to those who introduced me to an efficient way to heat things up. I said I will keep it short, I hope this helps get some wheels turning. To prevent a bottle neck past the heat riser if I use a 10" heat riser + 1.5" of insulation totaling 3", the remainder is 10". In the flow equation A = the Area of a cross section of the heat riser. I chose a 10" heat riser by using a basic formula based on the 23" diameter of the drum. If you take a look at the "ventury effect" you can see that a smaller opening will actually help increase the air speed over the burning sticks also improving the "rocketiness". ![]() I discovered with trial and error and calculations that the size of the intake is not as important as the size of the heat riser. I used Paul's portable rocket mass heater design and made some minor tweaks. In my stove I used fire brick, a 10" heat riser 1.5" thick and a 55 gallon drum. The other is the difference in temperature of the fire box and the outside air. The larger the heat riser, the faster the flow will be. The primary factor driving the force within the rocket stove is the "stack effect". I am in no way a math wiz and so I plugged these formulas into an excel spreadsheet and played with the numbers so I could make the most of the stove. My hope is to help everyone understand what is happening inside the Rocket Stove so they can improve their own designs. Because I am ADHD I hate wordy posts so I will try to keep it simple. Before I designed my Rocket Stove I consulted with my engineer brother-in-law who guided me in the right direction to understanding exactly what makes a Rocket Stove "rockety".
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