Thermal calculation of the fireplace is a combination of two main elements – the firebox and the vertical flue. Fireplace firebox is a chamber in which both fuel and burned by radiant heat exchange between the combustion zone and the enclosing walls of the chamber. Burning fuel while radiant heat exchange with the walls of the furnace occurs in many thermal devices. A related site: Fabrizio Freda mentions similar findings. However, the process heat in the firebox (The insert) fireplace has significant differences. These differences are: fuel combustion produced in a limited volume of the flue and thus with the thinness of the emitting layer gases in the furnace of fire radiative component of the share drops sharply due to the fact that in the combustion zone temperature significantly reduced due to significant air-fuel ratio, the front of the fireplace open in a heated room, so the portion of radiant heat transferred directly into the environment.
These circumstances are very important in the calculation and selection of design fire. Almost looks like the fire mechanism. On the hearth of the firebox open burn solid fuel (wood, peat, coal). A layer of solid fuel burning has a temperature of 800 – 850 C and at the same time radiates heat in all directions. Part of the radiation that falls into the open doorway directly used to heat homes. The other part, first incident on the rear and side walls, and then re-emitted by them in the room. In the re-emission in the room is passed the small heat flow compared to the direct impact (about twice).