Stove fans increase the heat produced by wood burning stoves by circulating the warm air directly into the room. Heat is therefore transferred by convection as well as radiation. This is claimed to heat an area more quickly and reduce the amount of logs required.
How Stove Fans Work:
Most stove fans use a Stirling engine which uses the heat of the wood burning stove to drive the fan. The Stirling engine was invented in 1816 by the Scottish inventor Robert Stirling. The fan is powered by the engine which is solely powered from the heat of the stove, the engine is powered by rapidly heating and cooling the same volume of air. When the air is heated, it expands, pushing a piston upward; when the same volume of air is rapidly cooled, it contracts, pulling the same piston downward, providing power. This expansion and contraction can operate at up to seven time a second, depending on the heat of the stove.