Expansion and Contraction Losses
There are other mechanisms in pipe flow that create head losses in addition to friction losses. Common sources of losses are due to expansion or contractions associated with geometry changes, valves, turns and flow splitting devices such as tees.
Head losses are computed using the equation
where KL is a loss coefficient. In some cases KL can be determined by analysis, while in other cases KL is determined using experiments. Values of KL for many practical flow conditions can be found in tables or handbooks. Note that the units for the head loss are associated with distance (m or ft). Thus they can be directly used with the “head” form of the Bernoulli equation. Head losses are placed on the outlet side of the Bernoulli equation while head creators (pumps, fans, etc.) are placed on the inlet side.
How losses other than friction losses are included in Bernoulli equation analyses of piping systems.