Pressure drop due to bends and fittings

The frictional effects of bends and fittings are often expressed in terms of a quantity called the velocity head drop . To introduce this concept, we begin by observing that the specific energy lost to friction, F(J/kg), for incompressible flow follows from an integration of the Fanning equation (4.20) with friction factor and velocity constant over the length of pipe  

It may be seen that K is the ratio of the energy lost to friction to the kinetic energy of the fluid flowing through the pipe. 

The change in pressure due to friction follows from integration of equation (4.19) when dz/dx = 0  

Estimates of losses in velocity heads for bends and a selection of fittings is given in Table 4.1. See Chapter 7, Section 7.8 for a discussion of and data on the velocity-head losses of globe and butterfly valves. 

Type of bend or fitting Frictional loss. K, in velocity heads 

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