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The purpose of pressurisation ductwork is to maintain positive pressure in building spaces to prevent smoke from entering from other spaces in which a fire is occurring. It is typically used in exit stairways, corridors, and lobbies.
Duct leakage test in the US. A duct leakage tester is a diagnostic tool designed to measure the airtightness of forced air heating, ventilating and air-conditioning (HVAC) ductwork. A duct leakage tester consists of a calibrated fan for measuring an air flow rate and a pressure sensing device to measure the pressure created by the fan flow.
A diffuser is "a device for reducing the velocity and increasing the static pressure of a fluid passing through a system”. [1] The fluid's static pressure rise as it passes through a duct is commonly referred to as pressure recovery. In contrast, a nozzle is used to increase the discharge velocity and lower the pressure of a fluid passing ...
This suction pressure operates to cause suction pressure collapse on the duct side walls. Also this pressure operates perpendicular to the duct "expansion joints" to create an additional load on the duct supports that adds to dead, and live loads. Please note: duct pressure loads vary with temperature, as the gas density varies with temperature ...
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.
Ducts for air pollution control in a 17000 standard cubic feet per minute regenerative thermal oxidizer (RTO). A round galvanized steel duct connecting to a typical diffuser Fire-resistance rated mechanical shaft with HVAC sheet metal ducting and copper piping, as well as "HOW" (Head-Of-Wall) joint between top of concrete block wall and underside of concrete slab, firestopped with ceramic ...
Air-blown cable installation requires the use of a device that injects a high volume of air into the duct, at pressures as high as 20-25 psi. The viscous drag forces generated by the rushing air along the length of the cable act to reduce or overcome the friction between the cable and the duct.
The pressure drop through a sound attenuator is typically higher than the pressure drop for an equivalent length of lined duct. However, significantly longer lengths of lined duct are required to achieve equal attenuation, at which point the pressure drop of large extents of lined duct is significantly greater than incurred through a single ...