Machinery's Handbook, 31st Edition
2784 Energy LOSS IN FITTINGS AND VALVES Equivalent Length Method: Pressure loss can be calculated for systems based on the equivalent length of straight pipe representing all pipe, fittings, and valves in the cir - cuit. Equivalent lengths of some common fittings and valves for liquids can be found in Table 26. Table 26. Equivalent Length in Feet of Selected Pipe Fittings and Valves for Liquid
Elbows
Standard Tee
Nominal Pipe Size (in.)
Square Corner
Flow thru Run
Flow thru Branch
90 ° Long Radius
90 ° Street
45 ° Street
90 ° Std.
45 ° Std.
1 ⁄ 4 1 ⁄ 2 3 ⁄ 4
0.9 1.6 2.1 2.6 3.5 4.0 5.5 6.2
0.5 0.8 1.1 1.4 1.8 2.1 2.8 3.3 4.1 5.4 8.1
0.6 1.0 1.4 1.7 2.3 2.7 4.3 5.1 6.3 8.3
1.5 2.6 3.4 4.4 5.8 6.7 8.6
0.8 1.3 1.8 2.3 3.0 3.5 4.5 5.4 6.6 8.7
1.7 3.0 3.9 5.0 6.5 7.6 9.8
0.6 1.0 1.4 1.7 2.3 2.7 4.3 5.1 6.3 8.3
1.8 4.0 5.1 6.0 6.9 8.1
1
1 1 ⁄ 4 1 1 ⁄ 2
2
12.0 14.3 16.3 22.1 32.2 39.9 50.1 59.7
2 1 ⁄ 2
10.3 12.8 16.8 25.3 33.3 41.8 49.7
11.7 14.6 19.1 28.8 37.9 47.6 56.7
3 4 6 8
7.7 10.1 15.2 20.0 25.1 29.8
12.5 16.5 20.7 24.7
13.1 17.3 21.7 25.9
12.5 16.5 20.7 24.7
10.6 13.4 15.9
10 12
Energy loss, in terms of pressure, for gas flow through fittings is often found using tabu lated values of pressure drops for fittings of different sizes. The equivalent length method can also be used, with pressure loss calculated in terms of the total equivalent length of all pipe and fittings. Table 27 includes some equivalent lengths of selected pneumatic fittings and valves. Table 27. Selected Pneumatic Fittings and Valves, Equivalent Lengths Pipe Size, inch Elbow Long Radius Elbow Close Return Bend Gate Valve Globe Valve 1 ⁄ 2 0.84 0.41 1.30 0.31 2.50 3 ⁄ 4 1.20 0.57 1.80 0.44 3.50 1 1.60 0.77 2.30 0.57 4.70 1 1 ⁄ 2 2.60 1.30 3.90 0.98 7.80 2 3.60 1.70 5.30 1.30 10.60 3 5.70 3.00 8.50 2.10 17.10 4 7.90 3.90 11.80 3.00 23.70 Entrance, Exit, Enlargement, and Contraction Losses for Subsonic Flow.— Any change in diameter of a pipe will cause energy losses in the fluid. Sudden Enlargement: Sudden enlargement of a pipe or tube causes minor losses due to turbulence. The friction loss, in terms of head, due to sudden enlargement can be approxi mated using the following equations:
v i 2 2 g ---
v i v o – ( )
2
2 g -----------
=
=
K
h l
A i A o --- –
2
=
1
K
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