Ducts
Some type of air-conditioning systems commonly use ducts to distribute air to a load like number of people, equipment and space. Air ducts are pathways or airflows used to ensure an acceptable indoor quality and thermal comfort.
A duct system is sometimes referred to as hvac ductwork. Duct design includes laying-out, sizing, detailing, optimizing, bending and troubleshooting the pressure loss in a duct system. It is also called hvac duct design.
Materials used in fabricating hvac ducts should be non-corrosive. Non-corrosive metals like tin was used in duct design. With advancements in steel production, the galvanization of steel to resist corrosion has made steel a replacement for tin in ductworks. Tin is more expensive than steel making the latter most feasible to use than the former.
Ducts can be in many different shapes. The rectangular-shaped duct is more popular as well as round and oval shapes in cross-sectional design. These shapes can be formed in these different materials:
Galvanized Steel
This metal sheet is a breakthrough in steel technology. Galvanized steel is used widely in ductworks because of its inexpensive price and non-corrosive properties. It can be customized in any form. Duct men or tin-knockers do the job in fabricating ducts using this material.
Polyurethane Duct Board
Polyurethane is a polymer made from organic materials mixing with a urethane sunstance. It is among the materials that can be customized to make a duct board. A new water-formulated product of rigid polyurethane panel board is an available and recommended option. The foaming process of this panel is achieved through the application or mixture of water instead of harmful and ozone-destructive gases like the CFC (chlorofluorocarbon), HCFC (hydrochloroflourocarbon), HFC ( hydroflourocarbon) and hydrocarbon.
Fiberglass Duct Board
Fiberglass panels are made from fiberglass blanket wrapped in a polymer facing. It is a good thermal insulation and sound-absorber, providing silent operation in the HVAC system.
Flexible Tubing
Flexible ducts, also called flex ducts are a convenient material for heating and cooling applications. It is easily attached to supply air grilles to a rigid duct system. The disadvantage of its use is the possibility of a pressure loss. Because of its flexible quality, limitation to its use in the duct system by HVAC installers is done to prevent or minimize turns of airflow.
A complete duct system contains many components. These are: vibration isolators; take-offs; stacks, boots and head; dampers and air terminals.
Vibration isolators are inserted into it (the duct system) at each end of the air handling unit. This is to block vibration caused by the blowers in the air handlers that would transmit noise to the inhabitants of the building.
Take-off is a fitting installed into the duct system. It is important in the diversion of airflow from the main duct into subsidiary ducts.
Stacks are vertical ducts and may be formed with a wide or a thin rectangular duct to the thin wall-mounted ducts. Stack boot is found at the. It supplied the transition from a larger round or rectangular-shaped duct to the slender wall-mounted duct. Stack head is the upper-end of the duct which provides a reverse transition of airflow to ducting while the register head makes the transition to wall-mounted or ceiling- mounted air grilles.
Dampers dispense a method of regulating air volume flowing to different parts of the duct system. Air terminals are conspicuously installed supply grilled or air outlets and exhaust air inlets.
A duct system is fabricated by a duct man or tin-knockers. The application of mathematical estimates and measurement, skill in metal crafting and the knowledge to use the correct materials are essential in duct works and duct design.