MechasFluid
ENERGY LINE AND HYDRAULIC GRADE LINE
Saturday, 30 May 2015 | 06:41 | 0 comment(s)
Energy
Line (EL)
Energy line (EL) shows total head for a certain
cross section in system.
For a fluid flow without any losses due to friction (major losses) or components (minor losses) - the energy line would be at a constant level. In a practical world the energy line decreases along the flow due to loses.
A turbine in the flow reduces the energy line and a pump or fan in the line increases the energy line.
Hydraulic Grade Line (HGL)
Hydraulic Grade Line (HGL) shows piezometric head for a certain cross section in system. The Hydraulic Grade Line is a line representing the total head available to the fluid - minus the velocity head and can be expressed as:
The Hydraulic Grade Line lies one velocity head below the energy line.
Example 1
Example 2
Example 3
Example 4
Example 5
Conclusion
- Energy Line always higher or same level with Hydraulic Grade Line.
- The difference between 2 line is the values of kinetic energy head,
- Major losses – cause Energy Line and Hydraulic Grade Line to decrease gradually
- Minor losses – cause Energy Line and Hydraulic Grade Line to decrease rapidly.
- Use of pump – Lines increased immediately
- Use of turbine – Lines decrease immediately
