6
ADC TEST STANDARDS
6.2 Performance Requirements
6.2.1 Thermal Performance.
Thermal loss properties of insulated flexible duct shall be based on flat sections of insulation only at installed duct wall thickness. Ratings shall exclude air film resistance, vapor retarders, or other duct components.
The thermal resistance (R) shall be determined using the relationship: R = th / k.
R = Thermal resistance (hr - ft 2 - °F/Btu) [(m 2 ·°C)/W] rounded to the nearest 0.1
Where:
th = duct insulation wall thickness (in.) [mm] rounded to the nearest 1/16 inch [2 mm]
k = measured apparent thermal conductivity (Btu - in/hr - ft 2 - °F) [W/(m·°C)]
The insulation thermal conductivity is measured according to ASTM C518 or ASTM C177 at 75°F [24°C] mean temperature. Installed insulation thickness is determined in the following manner (see notes 1 and 2 below).
{ Jacket Layflat Width x 2 3.14159
}
- Nom. Core Dia.
th =
2
The jacket layflat width can be determined by circumferentially cutting the jacket, removing it from the duct, laying it on a flat surface, and then measuring the width to the nearest 1/16 inch [2 mm].
Note 1 The out - of - package insulation thickness measured in accordance with ASTM C167 shall be equal to or greater than the calculated installed duct insulation wall thickness.
Note 2 Actual internal core diameter shall be within the tolerances of +3/8, - 0 in. [+9, - 0 mm] of nominal core diameter .
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6.2.2 Friction Loss
Friction loss shall be determined in accordance with the ADC Test Code FD 72 - R1 or in accordance with ASHRAE 120. Friction loss for straight runs shall be presented in graphical form over the manufacturer ’ s rated velocity range and diameter range. Friction loss in 90° bends shall be presented in graphical form at three different bend radii.
6.2.2.1 Straight Runs
Friction loss – inches of water gauge per 100 feet [Pa/m] of duct, shall be plotted on the horizontal axis, and “ Air volume – CFM [L/s] ” on the vertical axis. For convenience of the user, corresponding velocities may also be plotted. For purposes of recommended performance values in Section 6.1, a 12” [300mm] nominal internal duct size, tested at 1000 fpm [5.1 m/s] velocity shall be used.
6.2.2.2 90° Bends.
Friction loss coefficient (C o ) shall be plotted on the vertical axis and the internal duct diameter shall be plotted on the horizontal axis. Each R/D value tested shall be plotted. For purpose of recommended performance values for 12” [300 mm] nominal I.D. duct in Section 6.1, a loss coefficient of R/D = 2 shall be used.
The term C o is a dimensionless coefficient which represents the ratio of the total pressure loss to the dynamic pressure in terms of velocity pressure.
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