Duct (industrial exhaust)

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Industrial exhaust ducts are pipe systems that connect hoods to industrial chimneys through other components of exhaust systems like fan, collectors etc. Ducts are low-pressure pneumatic conveyors to convey dust, particles, shavings, fumes or chemical hazardous components from air in vicinity to a shop floor or any other specific locations like tanks, sanding machine, or laboratory hood. Ducts can be fabricated from a variety of materials including carbon steel and stainless steel. [1]

HVAC systems do not include this category of industrial application namely exhaust systems. A distinction from HVAC system duct 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.[2]

Fluid flow

The conveying fluid that flow through duct system is air. Air transports materials from hood to destination. It is also instrumental in capturing the material into the flow system. Air is a compressible 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 1) Identification of contaminants, its density and size, 2) Deciding of air flow 3) Sizing of the ductwork, 4) Calculation of resistance, 5) Finalizing the capacity of blower etc.[3] The aim 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

See also

  • Darcy friction factor Friction factor for designing duct systems.
  • HVAC
  • Colebrook equation
  • Process Duct Work

References

  1. ↑ Duct Work Assembly U.S. Bellows, (retrieved May 2012)
  2. ↑ ASHRAE Technical Committee 5.2 - Duct Design
  3. ↑ Industrial Duct System Design Fundamentals
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