ENERGY LOSSES FOR SUBSONIC FLOW Machinery's Handbook, 31st Edition
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0.6 0.5 0.4 0.3 0.2 0.1 0
Angle
15 30 45 60 90
K G
120 150
1.1 1.2 1.4 1.6 1.8 2 2.5 3 4 5 10 Di/Do
Fig. 6. Head Loss Coefficient K G , Conical Gradual Contraction Exit Loss: Discharge into to a static volume of fluid causes minor losses as the fluid loses its kinetic energy as its velocity drops to zero. This is called exit loss, and is calculated in terms of head using the following equation: h l v i 2 2 g = --- where v i is the velocity in the pipe before entering the reservoir. Entrance Loss: Entrance into a pipe from a static volume of fluid causes energy loss due to contraction turbulence. This is called entrance loss, and it is reduced by breaking the corners of the inlet with chamfers, or preferably, radii. Entrance head loss is calculated using the following equation and Table 28. h l K E v o 2 = where v o is the velocity in the pipe exiting the reservoir, and K E is the resistance coefficient for entrance. Table 28. Entrance Head Loss Coefficient, K E Condition K E Condition K E Rounded Inlet, R / D o : Square-edged Inlet 0.5 0.02 0.28 Chamfered Inlet 0.25 0.04 0.24 Inward Projecting Pipe 1 0.06 0.15 0.1 0.09 > 0.15 0.04 Fluid Power Valves There are many types of pneumatic and hydraulic valves. Valves can be normally open or normally closed. Normally open valves allow flow when the valve is not energized. Normally closed valves block flow when not energized. Valves may be actuated manu - ally or automatically. Automatic valves typically change state using solenoids, often as- sisted by energy from either internal or external pilot pressure. An external pilot supply should be used to control valve when the supply pressure to the valve is insufficient to shift the valve or when the medium being controlled by the valve would damage the shifting 2 g ---
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