ENERGY OR HEAD LOSS OF FLOWING FLUID

The change in velocity of the liquid in a flow (either in magnitude or direction) induces large-scale turbulence due to formation of eddies. So, a portion of energy possessed by the flowing liquid is ultimately dissipated as heat and is considered to be the loss of energy. Some of the losses of energy caused by the change in velocity are,

• Due to sudden enlargement
• Due to sudden contraction
• At the entrance to a pipe from large vessel
• At the exit from a pipe
• Due to an obstruction in the flow passage
• Due to gradual contraction or enlargement
• Due to bends
• In various pipe fittings

The above losses of energy are termed as 'minor' losses because the magnitude of these losses is quite small compared to the loss due to friction in long pipes (which are distinguished as 'major losses'). The 'minor losses' are confined to a very short length of the passage of the flowing liquid. The analytical expressions representing the loss of energy for above cases are discussed below.