Otherwise known as "Why dry wood is sooooooooo important:.
Lot's of people I know are burning (maybe attempting to burn) wood that has a moisture content of 35%+. On top of that, nearly every OWB owner I have dealt with has the wood pile conveniently stacked next to it out in the snow. As the commander on Police Academy said, "This is a very bad thing".
When you hear someone say that the moisture content of the wood is 35%, that means that out of a 10 pound chunk of wood, 3.5 pounds of that weight is water. Last I knew, water doesn't burn so that means it has to be evaporated before the wood can be turned to carbon and actually burn.
So let's take a few facts of physics and ponder them for a moment.
Fact one: 1 btu will heat one pound of water, 1 degree F. We want the water to evaporate so that means we have to raise the temp of the water from whatever temp it is in the wood (remember it's outside stacked by the boiler) so let's assume 10*. It has to go to 212* to vaporize and escape as steam. That translates to needing 202 BTU's to get our 1 pound of water to steam temp or 707btu's for 35% of our 10 pound chunk.
That's a fair amount of heat that's wasted just getting the water trapped in the wood up to 212* but it doesn't sound like a terrible amount. Certainly nothing worth the extra effort to let the wood dry...............Right?
Fact Two: Raising the water temp that 202* is not the only thing that's involved. We have to force that frozen water to change phase not once but twice. Change phase? What the heck is a phase change? Here's a hint. It has nothing to do with a gender operation.
Simply put: You have to change the water first from a solid to a liquid and then from a liquid to a gas. This is a very big deal and is where all the wasted heat from green wood comes from.
Water can exist at 32* as a solid (ice) and 32* as a liquid (water). At 212* it can be a liquid or a vapor. What makes it change even though the actual temp is the same? It's called latent heat or heat added/subtracted from a substance that causes a change of state (solid to liquid or liquid to gas)........5th grade physics.
So now the question is how many btu's are consumed making this phase change happen? That my friends is where the real numbers start to add up. The ice to water part is not significant, only about 3/10's of a btu per pound. Liquid to vapor however is another thing entirely. To change 1 pound of water in it's liquid form to 1 pound of vapor or steam if you will, takes a staggering 970btu's. Now that 3.5 pounds of liquid in our 10# chunk of wood is costing us nearly 4,000 btu's just to change it to vapor so it can evaporate as steam and get out of the way of the fire.
That should be enough to get some wheels turning and let you figure out the rest.
Is your wood cut split and stacked for next fall??? It's much less waste to let the sun do it rather than your fire.
Lot's of people I know are burning (maybe attempting to burn) wood that has a moisture content of 35%+. On top of that, nearly every OWB owner I have dealt with has the wood pile conveniently stacked next to it out in the snow. As the commander on Police Academy said, "This is a very bad thing".
When you hear someone say that the moisture content of the wood is 35%, that means that out of a 10 pound chunk of wood, 3.5 pounds of that weight is water. Last I knew, water doesn't burn so that means it has to be evaporated before the wood can be turned to carbon and actually burn.
So let's take a few facts of physics and ponder them for a moment.
Fact one: 1 btu will heat one pound of water, 1 degree F. We want the water to evaporate so that means we have to raise the temp of the water from whatever temp it is in the wood (remember it's outside stacked by the boiler) so let's assume 10*. It has to go to 212* to vaporize and escape as steam. That translates to needing 202 BTU's to get our 1 pound of water to steam temp or 707btu's for 35% of our 10 pound chunk.
That's a fair amount of heat that's wasted just getting the water trapped in the wood up to 212* but it doesn't sound like a terrible amount. Certainly nothing worth the extra effort to let the wood dry...............Right?
Fact Two: Raising the water temp that 202* is not the only thing that's involved. We have to force that frozen water to change phase not once but twice. Change phase? What the heck is a phase change? Here's a hint. It has nothing to do with a gender operation.
Simply put: You have to change the water first from a solid to a liquid and then from a liquid to a gas. This is a very big deal and is where all the wasted heat from green wood comes from.
Water can exist at 32* as a solid (ice) and 32* as a liquid (water). At 212* it can be a liquid or a vapor. What makes it change even though the actual temp is the same? It's called latent heat or heat added/subtracted from a substance that causes a change of state (solid to liquid or liquid to gas)........5th grade physics.
So now the question is how many btu's are consumed making this phase change happen? That my friends is where the real numbers start to add up. The ice to water part is not significant, only about 3/10's of a btu per pound. Liquid to vapor however is another thing entirely. To change 1 pound of water in it's liquid form to 1 pound of vapor or steam if you will, takes a staggering 970btu's. Now that 3.5 pounds of liquid in our 10# chunk of wood is costing us nearly 4,000 btu's just to change it to vapor so it can evaporate as steam and get out of the way of the fire.
That should be enough to get some wheels turning and let you figure out the rest.
Is your wood cut split and stacked for next fall??? It's much less waste to let the sun do it rather than your fire.
