We are interested in evaluating total KE across the section:
  
One can also evaluate KE based on the average velocity,  as
  
where
Kinetic energy correction factor is defined as
 
or

 It is left as an exercise to show that   
If the flow is turbulent,  is approximated between  

The advantage of defining  is now clear. For a tubular laminar flow, one can write the energy conservator equation in terms of average velocity, , without evaluating the complex integral:
 = constant 
KE correction factor