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Adjustable grille |
A grille
with linear blades which can be adjusted to vary the direction
of the discharged air. The linear blades are normally either
vertical or horizontal, or both horizontal and vertical. |
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Air
diffuser |
Supply
air terminal device, usually placed in the ceiling, generally
of circular, square or rectangular shape, and composed of divergent
deflecting members. |
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Air
diffusion |
Distribution
of the air in a space, called the treated space, by means of
devices, called air terminal devices, in
a manner so as to meet certain specified conditions,
such as air change rate, pressure, cleanliness, temperature,
humidity, air velocity and noise level. |
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Air
distribution |
The
transportation of a specified air flow to or from the treated
space or spaces, generally by means of ductwork. |
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Airflow |
Free
blowing airflow (at zero back pressure). Air performance are
measured according to DIN 24 163 and BSA BS 848.
Density of 1.2 kg/m³ at 20°C. |
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Air
terminal device |
A device
located in an opening provided at the boundaries of the treated
space to ensure a predetermined motion of air in this space.
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Ak
value
(of an air terminal device) |
Quotient
obtained by dividing a measured air flow rate by a measured
air velocity according to a specific process and a specific
instrument. |
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Coanda effect |
Also
called ceilling or wall efect.
Tendency of an air stream to fllow a wall plane when the stream
is in contact with the wall. The effect increases throw and
reduces drop. |
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Dampers
and valves |
Components inserted
into air ducts or devices which permit modification of the
air resistance of the system and consequently a change in
the air flow rate (dampers) or complete shut-off of the air
flow (valves) or control of the air flow rate and, in addition,
complete shut- off the air flow (control valves).
In particular, the following types, can be distinguished:
Multiple leaf dampers, comprising of a number of blades (or
shutters) of opposed or parallel leaf type.
Single leaf dampers (the flap being mounted at one end), commonly
called splitter dampers.
Hit-and-miss dampers, having two or more slotted slide mechanism.
Butterfly dampers, with two flaps in "V" arrangement.
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Drop
(Ld) (for supply air terminal device) |
Vertical
distance between the lowest horizontal plane tangent to specified
envelope and the core center.
The drop is generally referred to the envelope corresponding
to 0.25 m/s for specified negative value of supply temperature
differential (Refer to Fig. 1 A). |
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Dynamic
pressure (Pd) |
Pressure
produced by the movement of an air stream, expressed in mm H2O
or Pa (N/m2)
Pd = 0.6 v2 (Pa)
Pd = 0.061 v2 (mm H2O) |
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Effective
area (of an air terminal device) |
The
smallest net area of an air terminal device used by the air
stream in passing through the air terminal device. |
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Enclosure
class, motor |
IP code
is a coding system to indicate the degrees of protection provided
by an enclosure against access to hazardous parts, ingress of
solid foreign objects, ingress of water and to give additional
information in connection with such protection according to
IEC 529. A brief description for the first and second characteristic
numeral.
First characteristic numeral indicates ingress of solid foreign
objects:
2 = 12.5 mm diameter
4 = 1.0 mm diameter
5 = dust-protected
Second characteristic numeral indicates ingress of water with
harmful effects:
2 dripping (15° tilted)
4 Splashing |
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Envelope |
The
geometrical surface of the points of an air jet, corresponding
to a determined value of the measured air velocity. This velocity
is generally called «terminal velocity». |
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Exhaust |
The air flow
leaving the treated space. Exhaust may be accomplished by
one or more of the following methods:
a. Extraction: exhaust in such a manner that the air is discharged
into the atmosphere.
b. Relief: exhaust in such a manner that the air is allowed
to escape from the treated space if the pressure in that space
rises above a specified level.
c. Recirculation: exhaust in which the air is returned to
the air treatment system.
d. Transfer: exhaust in which air passes from the treated
space to another treated space. |
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Exhaust
air flow rate |
Volume
of air leaving an exhaust air terminal device within a time
unit. |
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Exhaust
air terminal device |
Air
terminaI device through which air leaves the treated space.
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Fire
valves (generally called fire dampers) |
Components
which are installed in an air distribution system between two
fire separating compartments and are designed to prevent propagation
of fire and/or smoke.
Generally are kept open by mechanical restraint, whose effect
is canceled under specific conditions. The valve is then closed
automatically. |
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Grille |
An air
terminal device with multiple passages for the air. |
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Induction |
Process
by which the primary air sets into motion an air volume, called
secondary air, in the room. |
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Induction ratio
(i) |
Ratio of the total
air flow rate to the primary air flow rate. |
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Lighting
troffer air terminal device |
An air
terminal device, usually in the form of a slot or combination
of slots, designed for use with a troffer unit. |
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Linear
air terminal device |
Air
terminal device (grille) with an aspect ratio of 10: 1 or more.
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Nominal
size of an air terminal device |
The
nominal size is the nominal value of the dimensions of the opening
which has been prepared for mounting the air terminal device
within. |
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Nominal
voltage / Frequency |
Maximum
voltage variation: +6%, -10% according to DIN IEC 38 and maximum
frequency. |
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Nozzle |
An air
terminal device designed to generate a low energy loss and thus
produce a maximum throw by minimum entertainment. |
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Primary
air flow rate |
Volume
of air entering a supply air terminal device within a time unit.
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Register |
A combined
grille and damper assembly. |
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Slot
air terminal device |
A device
with one or several slots with an aspect ratio of 10: 1 or more
for each slot (the aspect ratio is the ratio of the length to
the width of the closed rectangular opening). A slot may or
may not have an adjustable member to vary the direction of the
air jet(s) or air flow rate. |
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Sound
attenuators |
Components
which are inserted into the air distribution system and designed
to reduce airborne noise which is propagated along the ducts. |
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Sound
power |
Sound
power is the energy per time unit, watt, which the object submits.
Sound power is calculated from the sound pressure and is not
measured. The logarithmic decibel scale has been developed for
sound power in a similar way for sound pressure. Sound power
is not dependent of the room’s construction, and is therefore
easier to compare between different fans. |
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Sound
pressure |
Pressure
develops when pressure waves move in the air. Our ears translate
the pressure as sound. The sound pressure is measured in Pascal,
Pa.
The smallest sound pressure that the ear can appreciate is 0.00002
Pa, which is the threshold of hearing. The largest pressure
is 20 Pa, the upper threshold of hearing.
The large numerical difference in pressure between threshold
of hearing and the upper threshold of hearing, makes it difficult
to handle. A logarithmic scale is used to eliminate the large
numerical difference, which is based on the difference between
actual sound pressure level and the sound pressure at the threshold
of hearing. The scale has the unit decibel, dB, where the threshold
of hearing is 0 dB and the upper threshold of hearing is 120
dB. |
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Spread
(LS) (for a supply air terminal device) |
Maximum
distance between two vertical planes tangent to a specified
envelope and perpendicular to a plane through the core centre
(Refer to Fig. 1 B).
The spread are generally referred to the envelope corresponding
to 0.25 m/s for zero supply temperature differential (i.e.,
under isothermal conditions). |
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Static
pressure (Ps) |
Pressure
inside the duct which is necessary to overcome the friction
resistance. |
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Supply |
The
air flow entering the treated space. |
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Supply
air terminal device |
An air
terminal device through which air enters a treated space. It
usually consists of one or several deflecting members which
ensure reduction of the air velocity in the occupied zone as
well as efficient mixing of the supply air with the air in the
treated space. Moreover supply air terminal devices usually
determine the direction of the air jet(s). |
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Throw
(Lt) |
The
maximum distance between the centre of the core and a plane
which is tangent to a specified envelope and perpendicular to
the intended direction of flow (Refer to Fig. 1 A).
The throw is generally referred to as the envelope corresponding
to 0.25 m/s for zero supply temperature differential (i.e.,
under isothermal conditions). |
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Total
air flow rate (QL) |
Sum
of the primary and secondary air flow rates which are moved
in the treated space. |
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Total
pressure (Pt) |
Sum
of the dynamic and static pressures. |
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