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Ducts commonly also deliver ventilation air as part of the supply air. As such, air ducts are one method of ensuring acceptable indoor air quality as well as thermal comfort. A duct system is also called ductwork. Planning (laying out), sizing, optimizing, detailing, and finding the pressure losses through a duct system is called duct design. [2]
As indicated in GR-3155, cable is typically placed into the duct in one of three ways: It may be pre-installed by the duct manufacturer during the extrusion process. It may be pulled into the duct using a mechanically assisted or hand-drawn pull line. It may be blown into the duct using a high air volume cable blowing apparatus.
There are two major systems to classify ductwork airtightness, one based on European standards, the other based on ASHRAE standard 90.1-2010.Both are based on the leakage airflow rate at a given ductwork pressure divided by the product of the ductwork surface area and the same ductwork pressure raised to the power 0.65.
Rooftop HVAC unit with view of fresh-air intake vent Ventilation duct with outlet diffuser vent. These are installed throughout a building to move air in or out of rooms. In the middle is a damper to open and close the vent to allow more or less air to enter the space. The control circuit in a household HVAC installation.
The amount of ventilation in an ETS area is equal to the amount of an ETS-free area plus the amount V, where: V = DSD × VA × A/60E V = recommended extra flow rate in CFM (L/s) DSD = design smoking density (estimated number of cigarettes smoked per hour per unit area) VA = volume of ventilation air per cigarette for the room being designed (ft ...
A major consideration of duct design is to minimize duct pressure losses, turbulence, as poor duct geometry, increases turbulence, and increases plant electrical usage. Round duct work suction pressure collapse, in ducts over 6 feet in diameter, is prevented with rings at supports, and roughly 3 diameter centers.
The design of an effective kitchen ventilation system is determined by: The kitchen's workload; The amount, type and power of cooking equipment; The kitchen's layout and shape; The number of kitchen staff; The need for easy cleaning and maintenance; Energy efficiency; Hot air from cooking is usually vented externally through a chimney system.
HVAC turning vanes are sheet metal devices inside of mechanical ductwork used to smoothly direct air inside a duct where there is a change in direction, by reducing resistance and turbulence. See also