A chimney is a conduit for conveying airborne smoke and heat from a fireplace or other combustion source to the outside atmosphere. A chimney is often constructed with either masonry or metal, but wood may be used in some cases. The word “chimney” comes from Middle English “chimenea,” meaning “a vent; also: an excavation with vertical sides at the bottom through which flue gas can escape.”
The primary function of the typical chimney is to draw smoke away from rooms in a structure so that it does not accumulate to toxic concentrations. This is accomplished using stack gases, draperies, and dampers. All of these components are integral to the functioning of a chimney. fireplace repairs is built with a wall that has two functions: to guide the flow of rising smoke and to contain and extinguish the fire. The fire itself has two effects on the design of the chimney. First, it causes stack gas flow, which pushes smoke up into the chimney where it exits into the atmosphere; second, it generates radiant heat flux below the exit level in all but “dry smoke” conditions (when both fuel and air are excellent). The fire produces a very complex flow field, which can be understood as having three separate regions:
The bottom region is called the “flue. ” It is an enclosed region above the fire and below the smoke shelf. It has relatively low velocities and may even be laminar (laminar flow).
The smoke shelf is the zone where rising smoke from the fire first contacts an excellent surface. The upper boundary is called the “contact plane.” It separates the laminar flow region from what is usually a turbulent boundary layer.
The top region of a chimney has the highest velocity potential; this is where containment starts to fail if there are crevices or cracks in a non-fireproof chimney, allowing fire, hot gases, and toxic products of combustion to enter buildings. Fireplace and stove use is a significant source of soot and particulates in the atmosphere. Both are responsible for nearly half of all particulate pollution worldwide; and approximately a quarter of the carbon dioxide, methane, and nitrous oxide.
The combustion chamber is where fuel (wood) burns, generating heat energy (hence giving off smoke). Wood also produces carbon monoxide and other products which need to be removed from the chimney or flue system. The flue material usually consists of metal tubes made from galvanized iron or stainless steel, with smooth surfaces.