What Design Factors Help your Wood Stove Provide Heat?

Once the fuel is burning, the next task of a stove is to transfer as much heat as possible from the inside of the combustion chamber to the outside. This is also accomplished in a variety of ways and with varying degrees of efficiency. Most sim­ply, the mass of the stove is allowed to radiate.

 Radiate

Most stoves are of the radiant type; that is, of the energy they transfer from the inside of the stove to the atmosphere of the room, 60 to 80 percent is in radiant energy. The rest is natural convection. In the case of wood-burning heaters and soapstone stoves, radiation is blocked off and rechanneled to heat the surrounding and rising air almost entirely by convection. Other manufac­turers attach blowers and all sorts of gadgets to squeeze as much heat as possible from the stove. There is a limit, of course, as to how much heat can be extracted because the flue must be kept hot enough to create an adequate draft.

Surface Area

There are other important aspects of the successful diffusion of heat. The surface area of the stove is criti­cal in that, other things being equal, a larger surface will radiate more heat than will a smaller one. Some designers have ingeniously increased the surface area of their stoves without increasing the overall dimensions by fluting or embossing the sides with ornate designs, by creating inner chambers, or by stacking elaborate, arch­like heat exchangers on top of the stove.

Materials

The materials used in making a stove also affect the exchange of heat, but not so much as does the mass or weight of those materials. Virtually all modern stoves are made from either cast iron or steel. Both materials have nearly equal abilities to store and emit heat, given equal weight. A stove made from thin sheet metal, on the other hand, will transfer its heat faster and radiate more intensely than will a heavy-walled steel or cast-iron stove. It will not, however, give off more heat in total.

The tasks of stove design seem relatively simple— encourage and maintain complete combustion, and trans­mit the resultant heat to the room—but accomplishing these tasks is a complex and technologically sophisti­cated feat.

Tags: design, heat, wood burning stoves