Minor Losses Fluid Flow Equation

Minor Losses Fluid Flow Equation | Minor Loss in Pipe or Duct Components

The losses that occur in pipelines due to bends, elbows, joints, valves, etc. are sometimes called minor losses. This is a misnomer because in many cases these losses are more important than the losses due to pipe friction, considered in the preceding section. For all minor losses in turbulent flow, the head loss varies as the square of the velocity. Thus a convenient method of expressing the minor losses in flow is by means of a loss coefficient (K).

Values of the loss coefficient (K) for typical situations and fittings is found in standard handbooks. The form of Darcys equation used to calculate minor losses of individual fluid system components is expressed by Equation 3-15.

hm = K (V2/2g)


g = acceleration due to gravity = 32.174 ft/s 2 = 9.806 m/s 2 .
hm = head loss due to a fitting and has units of ft or m of fluid. It is the energy loss due to a fitting per unit weight of fluid.
K = minor loss coefficient for valves, bends, tees, and other fittings - table of minor loss coefficients .

The minor loss calculation is valid for open channels (including partially full culverts) as well as closed conduits (circular or non-circular) flowing full. The minor loss calculation does not check for unreasonable inputs such as negative values. All values should be entered as positive.

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