Open fires are made by arranging three bricks or stones (or another forum of tripod) on the level ground approximately 120 degree to each other. This is the most primitive cooking arrangement. The fuel used is generally firewood the size of which depends on the height of the stones or bricks.
Fire is started with some kindling material and then the wood is added. A temperature of about 300 degree centigrade is achieved in open fires or three stone cookstoves. Pots and pans are balanced on the three stones. When the stones get heated to 300 degree centigrade, the heat is transferred to the pots and some are transferred back to the fire.
Since the incoming air is also heated during combustion it reacts more easily with the wood gases at the glowing end of the stick. Combustion is controlled by moving the wood pieces. Energy to sustain the combustion comes from the radiation from the flame and from the glowing tips of fuel wood.
- millions of households throughout the world, particularly in Africa
- Rural people with nomadic habits
- Pavement dwellers in the city
- Construction workers for building roads and buildings who move from site to site.
- It is very versatile.
- They are easy to assemble and requires no particular skill.
- They satisfy many needs, such as cooking , drying out of the damp clothes, provides warmth, a source of light.
- It also acts as the focal point for social gatherings.
- Any solid combustible material can be used as fuel.
- The fuel can be of any size and dimension.
- The cooking vessels can be of any size and dimension as it only requires some adjustment of the stones to fit in the vessel.
- The smoke and the open fire keeps away insects and rodents.
- To construct a three stone fire costs nothing.
- The efficiency is very low hence fuel is wasted
- There is a lot of heat which is wasted due to the distance of the pot from the flame, convection and radiation losses from the pot walls
- Wind factor plays a major role in lowering the efficiency of the stove
- Heavy smoke from the fire causes eye irritation and respiratory diseases
- Fuel wood is becoming scarcer so steps should be taken to curb its use
Thus came in the need for Improved Stoves