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 typic ...

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 Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in Industrial sector, industry are commonly powered by compressed air or compressed inert gases. A central ...

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 su ...

, shavings,

fume Fume or fumes may refer to: * Fumé (grape), another name for the French wine grape Sauvignon blanc * Silica fume, a fine-grain, thin, and very high surface area silica * Fifi La Fume, a purple skunks teen character from the animated television ...

s, or chemical hazardous components from air in the vicinity to a shop floor or any other specific locations like tanks, sanding machines, or

laboratory hood A fume hood (sometimes called a fume cupboard or fume closet) is a type of local ventilation (architecture), ventilation device that is designed to limit exposure to hazardous or toxic fumes, vapors or dusts. Description A fume hood is typical ...

s. 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, cobalt ...

stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...

, 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 cloth ...

. 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. HV ...

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 Airflow, or air flow, is the movement of air. The primary cause of airflow is the existence of air. Air behaves in a fluid manner, meaning particles naturally flow from areas of higher pressure to those where the pressure is lower. Atmospheric ...

* 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