American Energy Systems Ovation - Manual (Page 49)

Version 7.1 49
Based on an understanding of FIGURE 28, it is obvious that properly seasoned dry
hardwood provides greater heat energy than moist, green, or softwood. The heat released
during the burn process thoroughly warms the firebox, thus sustaining combustion. An
Ovation’s firebox temperature can approach 2000
o Fahrenheit as complete combustion of
the exhaust gases occurs. These high temperatures will sustain an efficient burn and ensure
that the stove and chimney system remain clean. The list below gives a sample of ignition
temperatures for some of the carbon and volatile matters released when wood is burnt:
COMBUSTIBLE FORMULA IGNITION TEMP ( O F)
Fixed Carbon C 765 – 1115
Volatiles
Hydrogen H
2
1076 – 1094
Methane CH
4
1202 – 1382
Ethylene C
2
H
4
1008 – 1018
Benzene C
6
H
6
1364
Ethane C
2
H
6
968 – 1166
Carbon Monoxide CO 1191 – 1216
Note that all ignition temperatures for volatile matters given off by wood fall between
950
o F through 1400 o F. All visible flame emitted during a wood fire come from the
ignition of volatile matter. Good clean combustion occurs when the volatile wood fuel
vapors are thoroughly mixed with fresh combustion air. It is critical that enough
combustion fresh air is available to the stove during the burn process. Proper mixing of the
fuel and air ensures all fuel molecules come in contact with oxygen molecules. An
abundant amount of oxygen molecules react with the fuel molecules; otherwise, an
incomplete burn will occur. NOTE: The fuel-air mixture must ensure combustion
temperatures are always maintained as well as exceed the ignition temperature if a
continuous burn is to be sustained. It also takes time for the reaction to proceed. It is
commonly stated that good conditions for combustion are defined as the THREE T’s:
Turbulence _______________Temperature _______________________ Time
Good combustion requires turbulence in the fuel-air path to ensure that fuel and air
molecules are thoroughly mixed to ensure a complete burn process. It takes a certain
temperature, defined as Ignition Temperature, to sustain combustion. As volatile gases and
carbon matter are released from the wood fuel, they require time to combine with the
oxygen in the air. The combustion process is self-sustaining only if all conditions are met.
Heat is obtained from a stove by the thermal radiation that occurs from the burning of
wood. Although a fairly complex phenomena to define, the heat radiated from the fire is a
very strong function of the local (firebox chamber) temperature and the overall combustion
temperature that is maintained within a stove’s burn chamber. A relatively minor
combustion temperature increase in a wood stove can produce a significant amount of
increased heat output. NOTE: The reverse of the preceding statement is also true. That is,
if too much heat is pulled from the combustion chamber via heat exchanger tubes, the
combustion temperature can drop rapidly. This rapid drop of temperature will cause a