hydraulics

Innovyze H2OCalc Head loss due to Transitions and Fittings (Local loss)


3.7 Head loss due to Transitions and Fittings (Local loss)

Whenever flow velocity changes direction or magnitude in a conduit (e.g., at fittings, bends, and other appurtenances) added turbulence is induced. The energy associated with that turbulence is eventually dissipated into heat that produces a minor head loss, or local (or form) loss. The local (minor) loss associated with a particular fitting can be evaluated by

where V = mean velocity in the conduit (m/s, ft/s)

K = loss coefficient for the particular fitting involved.

The table given below provides the loss coefficients (K) for various transitions and fittings.

Table 3-3: Typical Minor Loss Coefficients

Type of form loss K
Expansion Sudden D1 < D2

Gradual D1/D2 = 0.8 0.03
D1/D2 = 0.5 0.08
D1/D2 = 0.2 0.13
Contraction Sudden D1 > D2

Gradual D2/D1 = 0.8 0.05
D2/D1 = 0.5 0.065
D2/D1 = 0.2 0.08
Pipe entrance Square-edge 0.5
Rounded 0.25
Projecting 0.8
Pipe exit Submerged pipe to still water 1.0
Tee Flow through run 0.6
Flow through side outlet 1.8
Orifice (Pipe diameter

/orifice diameter)

D/d = 4 4.8
D/d = 2 1.0
D/d = 1.33 0.24
Venturi (long-tube) (Pipe diameter

/throat diameter)

D/d = 3 1.1
D/d = 2 0.5
D/d = 1.33 0.2
Bend 90o miter bend with vanes 0.2
90o miter bend without vanes 1.1
45o miter bend 0.2
Type of form loss (continued) K
Bend 45o smooth bend:

(bend radius

/pipe diameter)

r/D = 1 0.37
r/D = 2 0.22
r/D = 4 0.2
90o smooth bend r/D = 1 0.5
r/D = 2 0.3
r/D = 4 0.25
Closed return bend 2.2
Sluice Submerged port in wall 0.8
As conduit contraction 0.5
Without top submergence 0.2
Valve Globe valve, fully open 10
Angel valve, fully open 5.0
Swing check valve, fully open 2.5
Gate valve, fully open 0.2
Gate valve, half open 5.6
Butterfly valve, fully open 1.2
Ball valve, fully open 0.1

Source: Nicklow and Boulos (2005)

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