Air terminal device

Ventilation for buildings - Air terminal devices - Aerodynamic testing of dampers and valves. Superseded BS 6821 1988... 

Ventilation noise originates primarily from fans and the air turbulence generated inside ducts and around supply air and exhaust air terminal devices. The appearance of the noise is, of course, affected by factors such as the speed of rotation and the power of the fan, and by how the fan is stabilized or in other ways acoustically insulated. The noise level and the frequency characteristics are also largely derermined by the velocity of the air inside ducts and around terminal devices, where factors such as the dimensions and appearance of the ducts and terminal devices may play a decisive role in the appearance of the noise. 

EN. 17.51, Ventilation for buildings—Air terminal devices—Aerodynamic testing of clampers and valves. 

Nielsen, P. V. The box method—A practical procedure for introduction of an air terminal device in CFD calculation. Report R9744, Dept, of Building Technology and Structural Engineering, Aalborg University, Aalborg, 1997. 

Air core area The gross area of the openings of an air terminal device (ATD). 

Complementary accessories for ATD components of the installation which are used in conjunction with, and in several cases form an integral part of, the air terminal device for the purpose of achieving the predetermined profile or rate of flow into or from the air terminal device (e.g., air flow controllers, dampers, flow equalizers, baffles, etc.), and... 

Fixed accessories for ATD, components of the installation which assist the fitting and fixing into place and/or maintenance of the air terminal devices and their complementary accessories (e.g., plaster frames, snap-in fasteners, etc.). 

Air terminal device (ATD) A specially designed component in an installation, which provides a predetermined air movement into or from a treated space. They are classified as... 

Core area of air terminal device That parr of an air terminal device located within a convex closed surface of the minimum area required to include all of the air terminal device openings inside the sur face. 

Displacement air diffusion Air diffusion where the mixing of supply air and room air external to the air terminal device is at a minimum. See also Air diffusion and Air terminal devices. 

Distance to the v isovel (displacement air) The maximum horizontal distance L from the center of an air terminal device to the rectangle circumscribing the specific isovel. It is independent of the distance from the floor. 

Externally mounted air terminal device A unit such as a louver that prevents the ingress of rain, snow, birds, etc., into the ductwork. 

Fixed air terminal device A component that has fixed (nonadjustable) parts. 

Fixing accessory of an ATD Any component that provides easy fitting and removal of air terminal devices. 

Free area of an ATD The area available in an air terminal device for the discharge of air, as opposed to the actual area. 

Grill An air terminal device with designed outlets for airflow and distribution. 

Induction supply ATD An air terminal device in which the primary air from the duct induces secondary airflow from the treated space in such a way that a high rate of mixing between the air from these two sources takes place within the device. 

Internally induced airflow rate of an ATD Volume of air induced into the primary airflow inside the air terminal device in unit time. 

Linear air diffuser An air terminal device with single or multiple slots, each of which has an aspect ratio not less than 10 1. Each slot may consist of a number of separate elements and may or may not have an adjustable member, W hich allows the directions of the air delivered to the treated space to be varied. 

Low-velocity ATD An air terminal device which is designed for thermally controlled ventilation, e.g., displacement flow applications. See also Air terminal device. 

Nominal size of an ATD The nominal value of dimensions of the prepared opening (duct) into which the air terminal device is to be fitted. For an air diffuser, the nominal size is generally defined as the duct size into which the neck of the device is fitted. 

Nozzle An air terminal device used to obtain the maximum conversion of static pressure to dynamic energy with minimum entrainment. 

Plenum box A component forming an interface between ductwork and one or more air terminal devices. By virtue of its design or by the inclusion of accessories, it can also be used to equalize the pressure/velocity across air terminal devices. 

Primary airflow rate The mass or volume of air entering a supply air terminal device in unit time from an upstream duct or a plenum box. Or the air leaving through an opening and entering a space. 

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