Are you an EPFL student looking for a semester project?
Work with us on data science and visualisation projects, and deploy your project as an app on top of Graph Search.
Concept
Oxyhydrogen
Summary
Oxyhydrogen is a mixture of hydrogen (H2) and oxygen (O2) gases. This gaseous mixture is used for torches to process refractory materials and was the first
gaseous mixture used for welding. Theoretically, a ratio of 2:1 hydrogen:oxygen is enough to achieve maximum efficiency; in practice a ratio 4:1 or 5:1 is needed to avoid an oxidizing flame.
This mixture may also be referred to as Knallgas (Scandinavian and German ; ), although some authors define knallgas to be a generic term for the mixture of fuel with the precise amount of oxygen required for complete combustion, thus 2:1 oxyhydrogen would be called "hydrogen-knallgas".
"Brown's gas" and HHO are terms for oxyhydrogen mainly encountered in fringe science.
Oxyhydrogen will combust when brought to its autoignition temperature. For the stoichiometric mixture in air, at normal atmospheric pressure, autoignition occurs at about 570 °C (1065 °F). The minimum energy required to ignite such a mixture, at lower temperatures, with a spark is about 20 microjoules. At standard temperature and pressure, oxyhydrogen can burn when it is between about 4% and 95% hydrogen by volume.
When ignited, the gas mixture converts to water vapor and releases energy, which sustains the reaction: 241.8 kJ of energy (LHV) for every mole of burned. The amount of heat energy released is independent of the mode of combustion, but the temperature of the flame varies. The maximum temperature of about is achieved with an exact stoichiometric mixture, about hotter than a hydrogen flame in air.
When either of the gases are mixed in excess of this ratio, or when mixed with an inert gas like nitrogen, the heat must spread throughout a greater quantity of matter and the flame temperature will be lower.
A pure stoichiometric mixture may be obtained by water electrolysis, which uses an electric current to dissociate the water molecules:
Electrolysis:
Combustion:
William Nicholson was the first to decompose water in this manner in 1800. In theory, the input energy of a closed system always equals the output energy, as the first law of thermodynamics states.
Official source
About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.