EL and HGL

The Total Head is constant along a stream line. This constant can be called the total head, H.
         Pressure Head - ρ / γ
         Velocity Head - v^2 / 2g
          Elevation Head – z
Piezometric Head – sum of pressure head and elevation head
                                          ρ/γ+z
Energy Line, EL – line that represent the total head available to the fluid
                             EL=H= ρ/γ+ v^2/2g+z

• Energy line decrease along the flow due to losses and be at a constant level without any losses. 

• A turbine in the flow reduces the energy line and pump/fan in the line increase the EL. 

• Measured by pitot tube

 Hydraulic Grade Line, HGL – representing piezometric head
                                        HGL= ρ/γ+z

• The HGL lies one velocity head below the EL 

Examples of EL and HGL

 

                                                                        Figure 5.1

El and HGL drop immediately in total energy head

                                         
                                                                        Figure 5.2