Economical oven for a small building
Bad weather gives the summer resident respite to search the Internet for ideas for arranging life and farming. And there are many of them: and one is better than the other. And I want a greenhouse and a summer kitchen, so that it can serve as a guest house. And all good undertakings are broken on the cornerstone of heating …
Having exhausted search engines with queries, I found an excellent solution for economical heating of small rooms with fuel, which
literally lying underfoot: waste from pruning the garden, chips and sawdust left after harvesting firewood, old boards and other wood materials.
This miracle oven was invented by American «survivors» who are preparing for the «nuclear winter» and the consequences of others, including natural disasters. They set out to find a simple and affordable heating device for self-production, which is distinguished by high efficiency and “omnivorousness”.
Have you heard of a jet oven? This is the result of their search. It must be admitted that this stove has more than one drawback, but the main one — it heats only small «one-room» rooms. Summer kitchens, greenhouses, guest houses and livestock sheds fall under this category.
Why look for something new when a Bulleryan-type furnace and its analogues will perfectly cope with the task? But it costs money, it doesn’t work on wet raw materials, you can’t cook on it and it’s impossible to lie down comfortably to “warm the bones”.
The rocket furnace in this regard is more functional and is done by hand from improvised means.
FOR INFORMATION. The heat transfer time of the reactive furnace is up to 12 hours from the moment the furnace is stopped and depends on the thickness of the heat storage layer. A Bulleryan-type furnace can operate up to 8 hours after fuel is loaded, but stops heating as soon as everything inside burns out.
Disadvantages of a rocket furnace: bulky and stationary, the need for frequent fueling and little experience in our realities.
WHAT TO FUEL
The firebox of a rocket stove is designed to burn wood fuel. These are fuel briquettes, and firewood, and pellets, moreover, the latter will provide a continuous supply (it is necessary to equip the structure with a bunker), which means they will free up your time.
The main thing! This stove will gladly absorb all wood debris: wood chips, bark, branches, sawdust, used plant supports and the remains of wooden boxes, all that you usually don’t know where to put in the fall after clearing the garden and vegetable garden.
IMPORTANT: the jet furnace will work even on crude fuel, only for this it is necessary to strictly observe the construction technology and proportions.
WHAT TO MAKE FROM
A jet heating stove is made from a combination of adobe, fireclay, solid bricks and metal.
Clay is used as a heat accumulator in the original. This malleable material allows for stunning designs, is relatively cheap, and is easily restored.
A small rocket oven for outdoor cooking can generally be built in 15 minutes from waste materials or welded in advance from metal.
The stove for cooking in the summer kitchen (without heating function) is made from a combination of brick and metal (hob). It does not have a riser lining (read on for what it is) and a heat-storing coating. The diagram is shown above.
Whatever you make a rocket oven from, it will still turn out to be environmentally friendly, because:
- works on wood, that is, it burns less oxygen than the tree produces during its lifetime;
- in its second chamber, afterburning of combustion products from the furnace takes place, which generally minimizes harmful emissions into the atmosphere (applies only to wood combustion products).
HOW IT WORKS
The most sensitive question: the scheme of operation of a jet furnace for heating. Scrupulous, because the scheme is simple and understandable, but no one gives the exact dimensions. But the network already has proportions derived by “our specialists”, which adapt American know-how to our standards and materials.
The original jet furnace is made from a 20-gallon metal cylinder. At our disposal may be a two-hundred-liter barrel or a fifty-liter gas cylinder. The maximum power of the furnace of them will be 25 and 15 kW, respectively.
The length of the lounger pipe for a stove from a barrel should not exceed 6 meters, for a stove from a gas cylinder — 4 meters.
Given that at the riser outlet (pipe in the second chamber), the combustion temperature can be up to 9000C, the thickness of the walls of a metal drum (barrel, cylinder) should not be thinner than 2 mm. The fact that the drum itself must be metal is beyond doubt, because the brick version will greatly reduce the efficiency for which this furnace is created.
Having accepted the fact that the combustion products are supplied to the chimney already cooled, its horizontal part can be made from a corrugated pipe.
PROPORTIONS OF INDIVIDUAL ELEMENTS OF THE ROCKET FURNACE
The following initial values were taken as the basis for calculations: D — diameter of the drum (barrel), S
is the internal area of its cross section. All names of the constituent elements are conditional!
Drum height H — cocgives 1.5-2 D.
At 2/3 of this height, the drum is thermally insulated (required!) With a coating of a mixture of clay and chopped straw (fireclay).
The thickness of the fireclay layer is 1/6 of D.
The height of the riser is selected so that between its upper part and the bottom of the barrel (cylinder) there is a gap of 7 cm, no less.
For the manufacture of the inner pipe of the riser, a profile pipe with a diameter of 1/4D is recommended, with a wall thickness of at least 3-4 mm. The same material and size is suitable for making a flame tube (primary firebox).
The riser pipe must be enclosed in an external circuit with a heat-intensive gasket (lining is made). For this purpose, a thin-walled pipe with a cross-sectional area in the range 4.5-6.5% of S; it is better to stay within 5-6% of S.
Material — any thin metal. Lining options for different types of drums are shown in the diagram below.
The space between the pipes is filled with sand with a high content of clay (in layers: moistened, tamped, dried, the next layer is added, etc.). It can be overlaid with fireclay bricks, but with obligatory backfilling of voids with sand. From above, the lining is “sealed” with clay coating.
Why is lining needed? To reduce the requirements for the parameters of a horizontal chimney and increase its length.
The length of the flame tube (for convenience, I duplicate the diagram below) is equal to the length of the inner tube of the riser.
NUANCE: for the stability of the furnace, it is recommended to make the flame tube square.
The question arises, what section should the flame tube be made of? In the source I used, this parameter is equal to the cross section of the inner pipe of the riser. In others, a fixed size of 150×150 mm is indicated.
Blower cross-sectional area = half of the riser cross-sectional area with an aspect ratio of 2:1.
Blower function: at the initial stage of kindling, it provides air flow and traction, the stove starts to work and … buzzes strongly (after all, reactive). To reduce the volume of the sound (by reducing the traction force), the ash pan (from the side of the blower) is gradually covered until the sound of a quiet hum is preserved, as in a conventional oven. So the fuel will burn out more slowly.
At the same time, it is necessary to close the valve to reasonable limits, which is equipped in the vertical part of the chimney, as well as in a conventional stove — to accumulate heat in the body of the lounger.
Secondary ash pan equip for cleaning soot from the drum. Use it once or twice a year important for the design tightness and thermal insulation, the door with subsequent clay putty as in the oven is not suitable (it is necessary to open too often), as well as the cast-iron ash pan door (leaky). Therefore, it is recommended to make it from metal with an overlay of mineral cardboard with four screws.
The volume of the secondary ash pan is 5% of the volume of the drum from the barrel or 10% of the volume of the drum from the cylinder.
Chimney area (including horizontal section) 1.5-2 square riser.
The length of the horizontal section is 6 m (for a barrel) and 4 m (for a cylinder).
The height of the external chimney is from 4 m.
Thickness of adobe cushion under the bottom wall of the chimney from 7 cm, if the lounger is installed on the boardwalk, it can be half as much.
The thickness of the adobe coating above the chimney is from 0.25D for a barrel to 0.5D for a gas cylinder. There is no more sense (it will not be able to warm up), less — the duration of heat transfer will decrease at the end of the furnace.
All calculated data are taken from this site.
IMPORTANT: before kindling the chimney, be sure to warm it up, for example, burn paper in the firebox. A warm chimney will create the draft necessary for the combustion process.
PS Those who do not have experience can make a trial version for heating a greenhouse. good try
inspire, unsuccessful one will tell you where to fix it.
So that the reader does not get the feeling that the jet stove is a solution for the poor, I give a photo report of one design company that designed a mansion in Switzerland.
In room. which we have no analogues (a two-level extension with a large hall on the ground floor and a mini-kitchen on the mezzanine the size of a one-bedroom apartment), we built a countertop with a sink, an electric stove, a cutting table and a hob based on a jet stove.
If you dig in the internet, you can find a drawing of this design (with dimensions :))
As they say in Odessa: «May you live like this!»
What else to read on the site:
The oven on the site is not such a useless attribute, if you really like to cook, here are a few pros. This is a unique aroma of dishes cooked «with smoke». This is cooking without electrical equipment. If you kindled the stove, then no whims of your electrical networks …
It is impossible to imagine how one can indifferently pass by the area where dishes are prepared on the grill. The fragrant smoke of the food being prepared, even if for a moment, will distract your mind from worldly worries and problems, forcing you to think about something more “monumental and eternal”…