Ductwork distribution

Are terminal HEPA filters on room air supplies necessary to prevent risk of product migration from one manufacturing area to another through ductwork distribution systems when air handling plant is inoperative ... 

Poor performance can result from fan inlet eccentric or spinning dow, and discharge ductwork that does not permit development of hiU fan pressure. Sometimes inlet restrictions starve a fan and limit performance. To obtain rated performance, the air must enter the fan uniformly over the inlet area without rotation or unusual turbulence. This allows all portions of the fan wheel to do equal work. If more air is distributed to one side of the wheel, such as with an elbow on the inlet, the work performed by the lightiy loaded portions of the wheel is reduced and capacity is decreased by 5—10%. The use of an inlet box duct on a fan can reduce capacity by as much as 25% unless there are turning vanes in the duct. Use of the vanes reduces the capacity loss to around 5%. 

When air is supplied lo a space by means of a fan forcing it along the ductwork, it has to be distributed into the space without causing drafts, noise, or poor air distribution, which would result in stagnant conditions in the space. Many variations of the following air-distribution merhods are possible. 

Air distribution The mechanical or natural delivery of air into a space in a designed tnanner, or the transport of air in ductwork. The components of air distribution are... 

Airflow pattern The air distribution within a space resulting from discharges from a fan or ductwork. 

Distribution ducting The supply or extract air ductwork, which conveys air from the plant room to the conditioned space and vice versa. 

Duct design The process of sizing ductwork to ensure the optimum performance in initial costs, running costs, and the distribution of air in a duct distribution system. The design techniques may be... 

A house is a complex system of interacting parts that contribute to overall performance including comfort, energy use, health, maintenance, and longevity. For example, a common air distribution system utilizes supply ducts running through the attic and return ducts tied directly to the air handler inside the home. If the ductwork is not properly sealed and there are combustion appliances in the home, this configuration can lead to health and fire hazards because the... 

Larger ducted ventilation systems, as used in offices and commercial premises using a central air-handling unit and fabricated distribution ductwork, are akin to air-conditioning systems but with less treatment to the air at the AHU (see Chapter 29). 

It is important that, to optimize the collection efficiency, the gas distribution across the frontal area of the precipitator must be as uniform as possible, although some recent work has indicated that for certain conditions a skewed velocity profile can be advantageous. It is not easy to produce a typical operational gas velocity of around 1.5m/s, which has been decelerated from approximately 15m/s in the inlet approach ductwork, and an acceptable standard of distribution is an RMS deviation of 15%. This standard can be achieved through field corrective testing, large-scale model tests, or the more recent CFD approaches.f ... 

A system that utilizes underfloor space for distribution of air rather than overhead plenum space or supply ductwork. 

Air mass flow distribution among mulhple burners with individual ductwork... 

Boot - In heating and cooiing system distribution ductwork, the transformation pieces connecting horizontai round ieaders to vertical rectangular stacks. 

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