Industrial exhaust ducts are pipe systems that connect hoods to industrial

chimney A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are t ...

s through other components of

exhaust system An exhaust system is used to guide reaction exhaust gases away from a controlled combustion inside an engine or stove. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes. Depending on the overall system ...

s like fans, collectors, etc. Ducts are low-pressure pneumatic conveyors to convey dust,

particles In the physical sciences, a particle (or corpuscule in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass. They vary greatly in size or quantity, from ...

, shavings, fumes, or chemical hazardous components from air in the vicinity to a shop floor or any other specific locations like tanks, sanding machines, or laboratory hoods. Ducts can be fabricated from a variety of materials including

carbon steel Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: * no minimum content is specified or required for chromium, coba ...

, stainless steel, PVC, and

fiberglass Fiberglass (American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cl ...

. They can be fabricated through rolling (preferable for ducts of 12" or more in diameter) or extruded (for ducts up to 18").

HVAC Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. ...

systems do not include this category of industrial application, namely exhaust systems. A distinction from HVAC system ducts is that the fluid (air) conveyed through the duct system may not be homogeneous. An industrial exhaust duct system is primarily a pneumatic conveying system and is basically governed by laws of flow of fluids.

Fluid flow

The conveying fluid that flows through the duct system is air. Air transports materials from the hood to a destination. It is also instrumental in capturing the material into the flow system. Air is a

compressible In thermodynamics and fluid mechanics, the compressibility (also known as the coefficient of compressibility or, if the temperature is held constant, the isothermal compressibility) is a measure of the instantaneous relative volume change of a f ...

fluid, but for engineering calculations, air is considered as incompressible as a simplification, without any significant errors.

Design

Process design of exhaust system will include * Identification of

contaminant Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, workplace, etc. Types of contamination Wi ...

s, their density and size * Deciding of air flow * Sizing of the ductwork * Calculation of resistance * Finalizing the capacity of blower, etc.
Industrial Duct System Design Fundamentals The goal is to keep contaminants out using minimum airflow. It is estimated that increase in an inch wg of static pressure can add a few thousands of dollars to the operation cost per annum.

References

{{DEFAULTSORT:Duct (Industrial Exhaust) Pollution

Fluid flow

Design

See also

References