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Flame temperatures

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Flame temperatures

Last updated April 6, 2005.

Flame temperature is not as simple as it sounds. It depends on many factors, such as:

Whether the (gaseous) fuel flow is laminar (smooth) or turbulent
Whether the fuel and oxidixer are premixed, or simply diffuse together while burning
Whether the flame is "adiabatic", meaning that it does not lose heat. While impossible in practice, the theoretical adiabatic temperature is often quoted.
Where in a (laminar) flame the temperature is measured
For flames in air, the temperature, humidity, pressure, present gas mixture, etc. of the air
The mixture of fuel vs. oxidixer in use. For example, an acetylene/oxygene flame may be neutral (equal mix: complete combustion, white rounded cone); carburising (excess acetylene: large smoky yellow flame); or oxidising (excess oxygen: short, sharp inner cone, deeper purple hissing flame).

Sites discussing practical welding and similar tasks tend to give much lower numbers than science-oriented sites, probably because of rapid heat loss in typical use. A number of sites warn that measurements done with thermocouples can be wildly inaccurate. More definitive information is available in the North American Combustion Handbook.

As a general practical guideline, consider one site's list of these heats for their jewelers' (gas/oxygen) torch:

2200°C = 3992°F, for Propane/Oxygen
2927°C = 5300°F, for MAPP Gas/Oxygen
2700°C = 4892°F, for Acetylene/Oxygen
3200°C = 5792°F, for Hydrogen/Oxygen

For their fuel/air torch they list:

1225°C = 2237°F with Propane-Butane Gas

For more theoretical/ideal values, consider this table (which also includes a few temperatures other than for gas/oxidixer mixtures):

Fuel and Oxidizer type	Temperature (Celsius)
Fluorescent light	60-80
Incandescent light	100-300
Cigarettes - unventilated conditions	288
Cigarettes - ventilated	400-780
Cigarettes - insulated and smoldering	510-621
Stove element	>550
Match	600-800
Tungsten halogen light	600-900
Candle flame	600-1,400
Electrical spark	1,316
Bunsen burner	1,570
Methanol/air	1,910
Methane/air	1,920-1,949
Butane/air	1,977
Propane/air	1,977
Wood/air (most organics are about here))	~1977
MAPP Gas/air
Hydrogen/air	2,210
Carbon monoxide/air	2,468
Acetylene/air	2,632
Acetylene/Oxygen	3,300
Hydrogen/Oxygen
Electrical arcing	<3,750
Plasma torch	~4,700
Lightning	30,000