Actually, since nobody burns ovendried wood, the hydrogen content (in the form of water), in the wood does count towards the total amount of heat energy that can be recovered from firewood. It's just in this case it works as a negative in the equation. Moisture in wood or bark fuel evaporates and absorbs energy in combustion, Generally, all moisture escapes in stack gases as heated water vapor. Heat in water vapor escapes and is no longer recoverable as it exits the heat recovery system in stack gases. Generally, higher fuel moisture content or hotter stack gas temperatures result in more heat escaping in stack gases. The following formula developed on the’ basis of heat capacity and latent heat of vaporization of water, is used to estimate the quantity of heat which escapes in stack gases because of fuel moisture per pound of wet wood or bark fuel. Stack gas heat loss caused by moisture (Btu/lb of wet fuel) = MC wb • [970 + (212 - T1) + (0.46 • (T2 - 212))] where T1 (°F) is the temperature of wood or bark fuel entering the furnace; T2 (°F) is temperature of stack gases beyond heat recovery devices; and MC wb is moisture content of the fuel on a wet weight basis expressed as a decimal fraction.
You are, of course, correct. I was trying to head off the inevitable "run your car (stove) on water" assertions based on a complete lack of understanding of physics and chemistry. The sense of deja vu related to an extended disagreement (in which you may have participated) about whether the presence of moisture in firewood reduced the heat available from a wood stove.
But Mr. W. ,,,, Extended disagreements are what forums are all about. Otherwise, where's the fun in it. Now I think we should "discuss" whether the effects of gamma radiation on firewood has any effect on burn times or creosote production.
Okay.. I'm back in on this thread.. So water in wood.... The ONLY way it comes into the heating calculation is in determining how much heat is lost from the fuel to evaporate the water in the wood. Sure there is hydrogen and oxygen in the water but the water molecule is so stable that it takes a TON of heat to break it as seen below. If anyone is running their stoves at these temperatures, they have more to worry about. Okay.. Someone else just posted on this.. Thermal decomposition of water[edit] Main article: Thermochemical cycle Thermal decomposition, also called thermolysis, is defined as a chemical reaction whereby a chemical substance breaks up into at least two chemical substances when heated. At elevated temperatures water molecules split into their atomic components hydrogen and oxygen. For example at 2200 °C about three percent of all H2O molecules are dissociated into various combinations of hydrogen and oxygen atoms, mostly H, H2, O, O2, and OH. Other reaction products like H2O2 or HO2 remain minor. At the very high temperature of 3000 °C more than half of the water molecules are decomposed, but at ambient temperatures only one molecule in 100 trillion dissociates by the effect of heat. However, catalysts can accelerate the dissociation of the water molecules at lower temperatures. Thermal water splitting has been investigated for hydrogen production since the 1960s.[13] The high temperatures needed to obtain substantial amounts of hydrogen impose severe requirements on the materials used in any thermal water splitting device. For industrial or commercial application, the material constraints have limited the success of applications for hydrogen production from direct thermal water splitting and with few exceptions most recent developments are in the area of the catalysis andthermochemical cycles.
