Introduction: Losses in Pipe: It is often necessary to determine the head loss, hL that occurs in a pipe flow so that the energy equation can be used in the analysis of pipe flow problems. The overall head loss for the pipe system consists of the head loss due to viscous effects in the straight pipes, termed the major loss and denoted hL-major. The head loss in various pipe components termed the minor loss and denoted hL-minor.
The head loss designations of “major” and “minor” do not necessarily reflect the relative importance of each type of loss. For a pipe system that contains many components and a relatively short length of pipe, the minor loss may actually be larger than the major loss.
Major Losses: The head loss, hLmajoris given as;
Where f is friction factor above mention equation is called the Darcy-Weisbach equation. It is valid for any fully developed, steady, incompressible pipe flow, whether the pipe is horizontal or on hill
Friction factor for laminar flow is ;
Friction factor for turbulent flow is based on Moody chart. It is because, in turbulent flow, Reynolds number and relative roughness influence the friction.
(Relative roughness is not present in the laminar flow)
The Moody chart is universally valid for all steady, fully developed, incompressible pipe flows. The following equation from Colebrook is valid for the entire non-laminar range of the Moody chart. It is called Colebrook formula.
Minor Losses:The additional components such as valves and bend add to the overall head loss of the system, which is turn alters the losses associated with the flow through the valves.
Minor losses termed as;
Where KL is the loss coefficient. Each geometry of pipe entrance has an associated loss coefficient.