The basic component of any wood-burning stove is the combustion chamber. In order to achieve a high combustion temperature it is necessary to insulate the combustion chamber. Normally, Vermiculite is used. This is a light material which, among other things, contains rock material/moler earth. Sometimes fire-resistant rock is used instead. Any combustion requires oxygen, this can be provided in a number of ways: The primary air at the bottom of the combustion chamber. The secondary air or scavenge air over the glass/door – also called the air wash system. The air for the air wash system should preferably be heated. Tertiary air, or mixed air, which is supplied through the holes at the rear of the stove, just above the firewood. The tertiary air should preferably be heated. The primary air makes it easier to ignite the firewood. However, it is important that the primary air supply is closed off once the flames have taken hold. The secondary air, or air wash system air has a basic function besides supplying the air for combustion. The air flows down over the glass and prevents the formation of condensation and soot particles on it. This reduces the formation of soot considerably. The tertiary air creates turbulence in the combustion chamber and helps the air and gasses to mix better whereby more complete combustion is achieved.
Smoke baffles Vermiculite of fire-resistant rock has an insulating effect but, of course, the heat from the flames needs to be transformed into heat in the room. Therefore, the smoke in the combustion chamber is converted via one or more smoke baffle plates. The flue gases come into contact with the stove’s steel components and these are heated up. The heat goes through the steel plates on the outside surface of the combustion chamber and the heat is transferred via the convection of the stove into the room. In addition, some of the heat on the glass is released into the room as radiation heat. Via this baffle system, the temperature is reduced from 700-750°C, to an average of around 250°C before the smoke goes out into the chimney. Efficiency A stove’s ability to burn off flue gases and its ability to cool them down and transmit the heat to the surroundings is an expression of the stove’s efficiency. A modern stove has an efficiency level of around 80%. An open log fire has an efficiency level of around 20%. A fire has an efficiency level of around 10%.