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DUCT DESIGN TABLES AND CHARTS

Table 14-1 DUCT MATERIAL ROUGHNESS FACTORS

AbsoluteRoughness Roughness E,

Duct Material Category ft mm

Uncoated carbon steel, clean (Moody 1944) Smooth 0.0001 0.03(0.00015 ft) (0.05 mm)

PVC plastic pipe (Swim 1982)(0.0003 to 0.00015 ft) (0.01 to 0.05 mm)

Aluminum (Hutchinson 1953)(0.00015 to 0.0002 ft) (0.04 to 0.06 mm)

Galvanized steel, longitudinal seams, 4 ft Medium 0.0003 0.09(1200 mm) joints (Griggs 1987) Smooth(0.00016 to 0.00032 ft) (0.05 to 0.1 mm)

Galvanized steel, spiral seam with 1, 2, and 3 (New Duct Friction Loss Chart)ribs, 12 ft (3600 mm) joints(Jones 1979, Griggs 1987)(0.00018 to 0.00038 ft) (0.05 to 0.12 mm)

Hot-dipped galvanized steel, longitudinal seams, Old 0.0005 0.152.5 ft Average(760 mm) joints (Wright 1945)(0.0005 ft) (0.15 mm)

Fibrous glass duct, rigid Medium 0.003 0.9rough

Fibrous glass duct liner, air side with facingmaterial (Swim 1978)(0.005 ft) (1.5 mm)

Fibrous glass duct liner, air side spray coated Rough 0.01 3.0(Swim 1978)(0.015 ft) (4.5 mm)

Flexible duct, metallic,(0.004 to 0.007 ft (1.2 to 2.1 mm) when fullyextended)

Flexible duct, all types of fabric and wire(0.0035 to 0.015 ft (1.0 to 4.6 mm)when fully extended)

Concrete (Moody 1944)(0.001 to 0.01 ft) (0.3 to 3.0 mm)

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CHAPTER 14

Figure 14-3 DUCT FRICTION LOSS CORRECTION FACTORS

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Table 14-3 CIRCULAR EQUIVALENTS OF RECTANGULAR DUCTS FOREQUAL FRICTION AND CAPACITY (Metric Units) (2)

Dimensions in mm

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CHAPTER 14

Cont. Table 14-3 CIRCULAR EQUIVALENTS OF RECTANGULAR DUCTS FOREQUAL FRICTION AND CAPACITY (Metric Units) (2)

Dimensions in mm

Equation for Circular Equivalent of a Rectangular Duct:

De = 1.30 [(ab)0.625/(a + b)0.250]

where

a = length of one side of rectangular duct, mm.b = length of adjacent side of rectangular duct, mm.

De = circular equivalent of rectangular duct for equal friction and capacity, mm.

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CHAPTER 14

Table 14-5 SPIRAL FLAT-OVAL DUCT (Nominal Sizes-Metric Units)(Diameter of round duct which will have the capacity

and friction equivalent to the actual duct size.)

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CHAPTER 14

Table 14-7 VELOCITIESNELOCITY PRESSURES (Metric Units)

Table 14-8 ANGULAR CONVERSIONDegrees Radians

10° 0.17520o 0.34930° 0.52440° 0.69850° 0.87360° 1.0570° 1.2280° 1.4090° 1.57 ( /2)

135° 2.36180° 3.14 ( )360° 6.28 (2 ) 14.17


Table 14-9 LOSS COEFFICIENTS FOR STRAIGHT-THROUGH FLOW

Figure 14-5 AIR DENSITY FRICTION CHART CORRECTION FACTORS

When an air distribution system is designed to oper-ate above 2000 feet (610 m) altitude, below 32°F(O°C), or above 120°F (49°C) temperature, the ductfriction loss obtained must be corrected for the air

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density. The actual airflow (cfm or I/s) is used to findthe duct friction loss which is multiplied by the correc-tion factor or factors from the above chart to obtainthe actual friction loss.

CHAPTER 14

B FITTING LOSSCOEFFICIENT TABLES

Duct Cross Section to which Coefficient "C" is referenced is at the top of each table. Negativenumbers indicate that the static regain exceeds the dynamic pressure loss of the fitting.

Table 14-10 LOSS COEFFICIENTS, ELBOWSUse the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

A. Elbow, Smooth Radius (Die Stamped), Round(2)

B. Elbow, Round, 3 to 5 pc--90o(2)

C. Elbow, Round, Mitered (15)

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U.S. UnitsFor Standard Air: (Metric Units)Re = 8.56 DV (Re = 66.4 DV)

where:D = duct diameter, inches (mm)V = duct velocity, fpm (m/s)

For Rectangular Ducts:


Table 14-10 LOSS COEFFICIENTS, ELBOWS (Cont.)Use the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

D. Elbow, Rectangular, Mitered (15)

E. Elbow, Rectangular, Mitered with Converging or Diverging Flow (15)

F. Elbow, Rectangular, Smooth Radius without Vanes (15)

U.S. UnitsFor Standard Air: (Metric Units)Re = 8.56 DV (Re = 66.4 DV)



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CHAPTER 14


G. Elbow, Rectangular, Smooth Radius with Splitter Vanes (2)

NOTES FOR THIS FIGURE ONLY:A) See Page 5.14 to calculate splitter vane spacing.B) CR = Curve RatioC) Use correction factors in Note 1 on .19 for elbows

other than 90°.

14.21



H. Elbow, Rectangular, Mitered with Turning Vanes(See Chapter 5, Sections E and H for additional information and data.)

I. Elbows, 90o, Rectangular, Z-Shaped (15)

14.22

U.S. UnitsFor Standard Air: (Metric Units)Re = 8.56 D V (Re = 66.4 DV)



CHAPTER 14


J. Elbows, 90o, Rectangular in Different Planes (15)(See Chapter 5, Section H for new data on spin-in fittings)

K. Elbows, 30o, Round, Offset (15)

L. Elbows, 90o, Rectangular Wye or Tee Shape


Table 14-11 LOSS COEFFICIENTS, TRANSITIONS (Diverging Flow)Use the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

A. Transition, Round, Conical (15)

U.S. Units (Metric Units)Re = 8.56 DV (Re = 66.4 DV)

where:

D = Upstream Diameter, inches (mm)V = Upstream Velocity, fpm (m/s)

B. Transition, Rectangular, Pyramidal (15)

Note 6: A = Area (Entering airstream), A1 = Area (Leaving airstream)

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CHAPTER 14

Table 14-11 LOSS COEFFICIENTS, TRANSITIONS (Diverging Flow) (Cont.)Use the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

C. Transition, Round to Rectangular (15)

D. Transition, Rectangular to Round (15)For Figures C and D, compute 0 using theequations and find the coefficient C fromTable 14-11B, Transition, Rectangular, Pyramidal.

E. Transition, Rectangular, Sides Straight (15)

F. Transition, Symmetric at Fan With Duct Sides Straight (15)

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Note 6: A = Area (Entering airstream), A1 = Area (Leaving airstream)


Table 14-11 LOSS COEFFICIENTS, TRANSITIONS (Diverging Flow) (Cont.)Use the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

G. Transition, Asymmetric at Fan With Duct Sides Straight, Top Level (15)

H. Transition, Asymmetric at Fan With Duct Sides Straight, Top 10° Down (15)

I. Transition, Asymmetric at Fan With Duct Sides Straight, Top 10° Up (15)

J. Transition, Pyramidal at Fan With Duct (15)

Note 6: A = Area (Entering airstream), A, = Area (Leaving airstream)

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CHAPTER 14

Table 14-12 LOSS COEFFICIENTS, TRANSITIONS (Converging Flow)Use the velocity pressure (Vp) of the downstream section. Fitting loss (TP) = C x Vp

A. Contraction, Round and Rectangular, Gradual to Abrupt (15)

Coefficient C (See Note 7)

AA 10° 15°-40° st0 120° 150 180100 15'-40' 50'-60' 900 1200 1500 1800

2 0.05 0.05 0.06 0.12 0.18 0.24 0.264 0.05 0.04 0.07 0.17 0.27 0.35 0.416 0.05 . 0.04 0.07 0.18 0.28 0.36 0.42

10 0.05 0.05 0.08 0.19 0.29 0.37 0.43

B. Contraction, Conical, Round and Rectangular (15)

Coefficient C = K Co 0 is major angle for rectangular transition

Note 7: Al = Area (Entering airstream), A = Area (Leaving airstream)

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When O = 180°


Table 14-12 LOSS COEFFICIENTS, TRANSITIONS (Converging Flow) (Cont.)Use the velocity pressure (Vp) of the downstream section. Fitting loss (TP) = C x Vp

C. Contraction, Rectangular Slot to Round (15)

Note 7: Al = Area (Entering airstream), A = Area (Leaving airstream)

Note 8: A = Area, Q = Airflow, V = Velocity

14.28

Table 14-13 LOSS COEFFICIENTS, CONVERGING JUNCTIONS (Tees, Wyes)Use the velocity pressure (Vp) of the downstream section. Fitting loss (TP) = C x Vp

A. Converging Wye, Round(2)

CHAPTER 14

Table 14-13 LOSS COEFFICIENTS, CONVERGING JUNCTIONS (Cont.)Use the velocity pressure (Vp) of the downstream section. Fitting loss (TP) = C x Vp

B. Converging Tee, 90°, Round (15)

C. Converging Tee, Round Branch to Rectangular Main

D. Converging Tee, Rectangular Main and Branch


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E. Converging Wye, Conical, Round (2

F. Converging Tee, 45o Entry Branch to Rectangular Main


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CHAPTER 14


G. Symmetrical Wye, Dovetail, Rectangular (15)


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H. Converging Wye, Rectangular(15)

I. Wye, Rectangular and Round (15)

When:Alb = A2b

Ac = Alb + A2b


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CHAPTER 14

Table 14-14 LOSS COEFFICIENTS, DIVERGING JUNCTIONS (Tees, Wyes)Use the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

A. Tee or Wye, 30o to 90o, Round (15)


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Table 14-14 LOSS COEFFICIENTS, DIVERGING JUNCTIONS (Cont.)Use the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

B. 90o Conical Tee, Round(2)

C. 45o Conical Wye, Round (2)

D. 90° Tee, Round, Rolled 45o with45o Elbow, Branch 90o to Main(2)

E. 90° Tee, Round, with90° Elbow, Branch 90° to Main (2)


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CHAPTER 14


F. 90o Tee, Round, Rolled 45o with 60o Elbow, Branch 45o to Main(2)

G. 90o Conical Tee, Round, Rolled 45o with 45o Elbow, Branch 90o to Main(2)

H. 90o Conical Tee, Round, Rolled 45o with 60o Elbow, Branch 45o to Main(2)

I. 45° Wye, Round, Rolled 45o with 60o Elbow, Branch 90o to Main(2)


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J. 45o Conical Wye, Round, Rolled 45o with60o Elbow, Branch 90° to Main(2)

K. 45o Wye, Round, Rolled 45o with30o Elbow, Branch 45o to Main(2)

L. 45o Conical Wye, Round, Rolled 45o with30o Elbow, Branch 45° to Main(2)


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CHAPTER 14


M. 45o Wye, Conical Main and Branch with 45o Elbow, Branch 90° to Main (15)

N. Tee, 45° Entry, Rectangular Main and Branch

P. Tee, 45o Entry, Rectangular Main and Branch with Damper

14.37



Q. Tee, Rectangular Main and Branch

R. Tee, Rectangular Main and Branch with Damper

S. Tee, Rectangular Main and Branch with Extractor

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CHAPTER 14


T. Tee, Rectangular Main to Round Branch

U. Wye, Rectangular (15)

14.39



V. Tee Rectangular Main to Conical Branch (2)

W. Wye, Rectangular (15)

X. Symmetrical Wye, Dovetail, Rectangular (15)

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CHAPTER 14

Table 14-14 LOSS COEFFICIENTS, DIVERGING JUNCTIONS (Cont.)Use the velocity pressure (VP) of the upstream section. Fitting loss (TP) = C x Vp

Y. Wye, Rectangular and Round (15)

Z. Tee, Rectangular Reducing, 45° Entry Branch(2)

Table 14-15 LOSS COEFFICIENTS, ENTRIESUse the velocity pressure (Vp) of the downstream section. Fitting loss (TP) = C x Vp

A. Duct Mounted in Wall, Round and Rectangular (15)

14.41


Table 14-15 LOSS COEFFICIENTS, ENTRIES (Cont.)Use the velocity pressure (Vp) of the downstream section. Fitting loss (TP) = C x Vp

B. Smooth Converging Bellmouth, Round, without End Wall (15)

C. Smooth Converging Bellmouth, Round, with End Wall (15)

D. Conical, Converging Bellmouth, Round and Rectangular without End Wall (15)

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CHAPTER 14


E. Conical, Converging Bellmouth, Round and Rectangular, with End Wall (15)

F. Intake Hood (15)

G. Hood, Tapered, Flanged or Unflanged(2)

Note 9: With screen in opening at Ds, Cs = C (from table) + C (Screen coef. Table 14-17)

where: A= Area at D; As = Area at Ds As)214.43



H. Hood, Canopy Island or Range

I. Hood, Slot (Dishwasher)

Table 14-16 LOSS COEFFICIENTS, EXITSUse the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

A. Exhaust Hood (15)

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CHAPTER 14

Table 14-16 LOSS COEFFICIENTS, EXITS (Cont.).Use the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

B. Exit, Conical, Round, with or without a Wall (15)

C. Exit, Plane Diffuser, Rectangular, with or without a Wall (15)

D. Exit, Pyramidal Diffuser, Rectangular,with or without a Wall (15)

14.45


Table 14-16 LOSS COEFFICIENTS, EXITS (Cont.)Use the velocity pressure (VP) of the upstream section. Fitting loss (TP) = C x Vp

E. Exit, Discharge to Atmosphere from a 90o Elbow, Round and Rectangular (15)

F. Exit, Duct Flush with Wall, Flow along Wall (15)

14.46

A

RECTANGULAR: Coefficient C (See Note 11)

L/WR/W

0 0.5 1.0 1.5 2.0 3.0 4.0 6.0 8.0 12.0Note:

0 3.0 3.1 3.2 3.0 2.7 2.4 2.2 2.1 2.1 2.0In loss coefficient. 0.75 2.2 2.2 2.1 1.8 1.7 1.6 1.6 1.5 1.5 1.5

1.0 1.8 1.5 1,4 1,4 1.3 1.3 1.2 1.2 1.2 1.21.5 1.5 1.2 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.12.5 1.2 1.1 1.1 1.0 1.0 1.0 1.0 1.0 1.0 1.0

ROUND: Coefficient C (See Note 10)

L/D 0.9 1.3 When:

C 1.5 1.4 R/D = 1.0 (Round)

CHAPTER 14

Table 14-16 LOSS COEFFICIENTS, EXITS (Cont.)Use the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

G. Plane Asymmetric Diffuser at Fan Outlet without Ductwork (15)

H. Pyramidal Diffuser at Fan Outlet without Ductwork (15)

I. Fan, Free Discharge, Plenum

J. Exit, Abrupt, Round and Rectangular, with or without a Wall (15)

14.47


Table 14-17 LOSS COEFFICIENTS, SCREENS AND PLATESUse the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

A. Screen in Duct, Round and Rectangular (15)

B. Perforated Plate in Duct, Thick, Round and Rectangular (15)

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CHAPTER 14

Table 14-18 LOSS COEFFICIENTS, OBSTRUCTIONS (Constant Velocities)Use the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

A. Damper, Butterfly, Thin Plate, Round(15)

B. Damper, Butterfly, Thin Plate, Rectangular(15)

C. Damper, Gate, Round(15)

14.49


Table 14-18 LOSS COEFFICIENTS, OBSTRUCTIONS (Constant Velocities) (Cont.)Use the velocity pressure (Vp) of the upstream section. Fitting loss (TP) = C x Vp

D. Damper, Gate, Rectangular(15)

E. Damper, Rectangular, Parallel Blades (2)

F. Damper, Rectangular, Opposed Blades (2)

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CHAPTER 14


G. Damper, Butterfly, Airfoil Blade, Rectangular(15)

H. Obstruction, Smooth Cylinder in Round and Rectangular Ducts(15)

I. Round Duct, Depressed to Avoid an Obstruction

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J. Rectangular Duct, Depressed to Avoid an Obstruction

K. Rectangular Duct with 4-45° Smooth Radius Ells to Avoid an Obstruction

L. Rectangular Duct with 4-90° Mitered Ells to Avoid an Obstruction

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