Fire Science

a Skill-Building Sampler from www.ErnieAndErica.Info

There have been myriad attempts to define what distinguishes humans from other animals, and most suggestions leave something to be desired. (Aristotle tried "featherless biped" and got a plucked chicken thrown over his academy wall. Opposable thumbs? That would make us a sort of defective chimpanzee with paws for feet, wouldn't it?)

I personally suspect there isn't any single distinction. That could be important, actually. Acknowledging our animal nature gives us a kinship with the natural world, and a better understanding of our own behavior.

But ...
There's been an awful lot of people playing with fire for an awful long time, and not a lot of other critters messing with it.

(Not a lot of other critters read web pages, either, so I can safely assume you're a people-type critter. You probably know something about fire, then, don'cha? Byt maybe not as much as other peoples, who grew up playing with it instead of with computers.)

Some things most people know about fire:

1) It's hot.

2) It burns [fuel].

3) You can put it out [smother it with dirt; starve it of fuel; interrupt it with air or water to chill its heart, or a shovel to scatter its bones]. This is the "fire triangle:" fuel, air, and heat. Take any one away, and no more fire.

4) Heat can start it -- if it gets too big/hot, you can't blow it out anymore.... (That's right... you just aren't cool enough.)

5) Flames tend to go up. Hot air rises. It's hot above a fire. (But it's also hot all around it ...)

6) Fire is bright, and it can makes things glow. (Visible glowing radiation means it's over a thousand degrees, unless it's some fancy stuff like LED's or glow-worms.)

7) Fire makes soot, smoke, and invisible gases that we can't breathe. (at least, not safely).

Some things not everybody knows about fire:

1) You can direct the heat from it. Put a wall behind it, and some of the heat bounces back across toward you. Put it in a box (like a big square fireplace) and the heat stays near the center and goes straight up if there's no lid. Great for cooking. Rings of fire are pretty good for this, too.

2) A pipe, tube, chimney, or hollow log can function as a "hot stack." The tube gives the gases a place to go that they don't get tumbled by cold air coming in from the sides. The hotter the tube gets, the faster the gas inside it rise, drawing more air across the fire and channeling exhaust gases up and away. A tube or chimney acts like a "smoke vacuum," and can very quickly turn a smouldering campfire into a rushing tower of flame.

3) Smoke is unburned fuel. If you can burn your fuel completely, so there's no smoke,
a) you need a lot less fuel to get the job done, in most cases, and
b) you don't get so much turpentine, methanol, soot, nitrous oxides, carbon monoxide, and all those other nasty things that make people cough and rub their eyes then they get a faceful of smoke. When fire burns completely, it turns carbohydrate fuels (like wood/grass/paper) and hydrocarbon fuels (like oil/wax/fats) into... carbon dioxide, and water. It's just a lot of carbon and hydrogen, getting completely oxidized.

(Side rant: Yes, carbon dioxide is building up in our atmosphere. It's a product of all our combustion technologies -- smelting ores to make metals, burning gas and coal for fuel, refining limestone into lime and cement, and powering our houses and computers with the electricity produced in far-off, coal-burning plants made from cement and metal. A little carbon dioxide from a very small, clean-burning fire might just be a better alternative to a hidden carbon-billowing industrial process, and it's certainly better than a lot of dirty smoke.

If it helps, methane is an even worse greenhouse gas. So stop eating beans. And water is the worst of all. But we need it to survive.

These substances aren't "bad" as such, they're potentially "good" elements in a system that's currently out of balance. Burning massive amounts of fossil fuels over a short period (a few hundred years) releases long-trapped carbon, destabilizing the climate. As an individual, you can't put it back the way it was. But if you can grow enough fuel on your own land to provide for your needs, without depleting your woodlot, you know that your plants are pulling that carbon back out of the air as fast as you put it in. You can even return the mineral ashes to the same forest, and encourage them with a little rich food (your waste) now and then. It's not "waste" that's the problem, it's wasted waste.)

4) Air is a fluid, so are smoke and water. You can use the same tools to channel hot air that you use to hold and move water -- you just have to turn them upside down. And upside-down bucket is an oven or hot-air balloon. An upside-down pipe is still a pipe, or a duct. An upside-down drain is a chimney. And an upside-down siphon is.... well, it's something that most people haven't really thought about using on a fire. We call it a "j-tube," or an "l-tube," and it's a thing that can make fire burn sideways. Ancients used them to make long, hot furnaces for heating palaces, firing ceramics, and processing ores.

5) Remember convection, conduction, radiation?
Convection is hot air rising and wind blowing, sunlight on your face is radiation, conduction is why a good cuddle or hot shower is a lot warmer than watching one.
A chimney facilitates convection, but it can also pump heat straight out of your house. Some elegant fireplaces use reflective masonry to bounce radiation back at us (with dish-like diagonal walls). Like cats, many of us like to sit on a warm surface as well. As long as your body is between the fireplace glow and the cold chair, your seat will only get as warm as your shadow.
Conduction is the process of transferring heat by touch -- and it's by far the most direct way to transfer heat. It's like radiation with zero distance -- heat transfer is limited only by the materials themselves. But we rarely use it for comfortable heat-- stoves are too hot, hearths too sooty, water-bottles and hot showers are too leaky and wet to use while reading a good book. Microvavable heat-packs and too-hot-to-drink coffee mugs are about the extent of it.

6) If we use everything we know about fire, we can get it to do amazing things, just by how we arrange ordinary materials like bricks, metal, cardboard, rocks, clay, or whatever suits our purposes.

On www.ErnieAndErica.info, there follow a series of demonstration photos and diagrams, showing a variety of nifty fireplaces, stoves, and heating devices. Unfortunately, I don't do photos in this journal, as many of you have commented.
But I'll suggest links:

RocketStoves.Com
Erica's Photos
and of course, www.ErnieAndErica.Info