Chimney Science Flashcards
What are the byproducts of complete combustion?
water vapor, carbon dioxide, heat, and noncombustible gases.
Complete combustion rarely happens.
What are the three heat transfer methods?
- Conduction- heat transfer through solid objects
- Radiation- When an object hotter than its surroundings emits infrared radiation in straight lines in all directions.
3.Convection- heat rises and cool air lowers creating a convective current. Many convective heaters have fans.
What are the different types of gas and what can gas produce?
Natural gas- lighter than air.
Liquified petroleum- aka propane. heavier than air.
Water vapor is produced which can affect the masonry through efflorescence and freeze-thaw damage.
What is combustion?
The rapid oxidation of fuel resulting in the release of energy, usually in the form of heat and light.
Requires adequate heat, oxygen, and fuel with a chemical reaction, aka “the fire tetrahedron.”
heat is used to heat fuel hot enough for combustion, drive away moisture, and the useful heat we feel. A certain amount of heat is carried up the chimney to provide DRAFT.
What is the preferred moisture content in wood for burning?
15-25 percent
What issues can fuel oil pose to a venting system?
Produce sulfuric soot.
Dyes added to the oil cause staining resembling rust on the outside of chimneys and green deposits on liners and connector pipes.
When converting to gas from oil, flue needs cleaning and a new liner to prevent sulfuric paste.
What factors affect creosote deposits?
Smoke Density
Moisture content
Flue gas temperature which is influenced by chimney type, size, location, bends, etc
Residence time
Large fuel loads
Appliance factors (too big, installed without adjusting flue size)
proper woodstove operation (air controls, fuel load. Should see 1ft plume of steam 1ft above chimney top.)
What is combustion efficiency?
The percentage of potential chemical energy contained in the fuel that is converted to useful heat inside the fire chamber
What is the preferred moisture content in pellets?
8-10 percent
What are the reasons for removing creosote?
If more than 1/8in buildup, should be removed in order to properly inspect chimney.
Creosote increases risk of chimney fires
Creosote is acidic and corrodes connectors, steel, and mortar.
Creosote expands with heat, closing up the flue
Creosote can leave watery, messy puddles and odor in the home.
What are the different types of coal?
hard aka anthracite- comes in egg, stove, chestnut, pea, nut, and buckwheat
soft aka bituminous- comes in lump, egg, nut, stoker, slack, and fireplace coal/cannel coal
Coal has 2 1/2x more BTUs per lb than wood.
What are the proper clearances to combustibles for woodstoves?
Unlisted- 36”, but NFPA 211 contains clearance reduction methods, never less that 12” and 6” for stove connector pipes.
Listed- manufactures manual
What is draft?
the FORCE or pressure difference between the inside of the venting system that causes gases to flow up and out the chimney and air to flow into the appliances.
A measure of the FORCE that drives the venting system.
Chimney height and temp difference to outside air affect draft.
What is carbon monoxide?
Another result of incomplete combustion. (Complete combustion creates carbon dioxide)
It blocks oxygen from getting to vital organs, causing fainting and/or death.
What is pyrolysis?
A chemical change brought about by the action of heat.
Over time with consistent exposure to heat, pyrolysis lowers the temperature at which the wood/combustible will ignite.
