Summary

When a fluid moves from a tank or vessel into a pipe system or vice versa there are pressure losses. This article provides K-values for pipe entrances and exits of various geometries. These K-values may be used to determine the pressure loss from a fluid flowing through these entrances and exits.

Definitions

:Pipe Diameter
:K-value or excess head
:radius of rounded pipe inlet


Calculating Entrance and Exit Losses

Listed below are K-values for several common entrance and exit geometries. These may be used in conjunction with the velocity of the fluid in the pipe to calculate the entrance and exit pressure losses. Refer to the article on pressure loss calculation using the K-value or excess head method for the formula by which the pressure loss may be calculated from the K values below.

K-values for Pipe Entrances

The table below presents the K-value for pipe entrances of various geometries.

Type Shape r/D K-value
Flush/Square-Edged Square Edged Pipe Entrance 0 K = 0.5
Rounded Rounded Pipe Entrance 0.02 K = 0.28
0.04 K = 0.24
0.06 K = 0.15
0.10 K = 0.09
0.15+ K = 0.04
Inward Projecting/Re-entrant Re-entrant Pipe Entrance - K = 0.78
Chamfered Chamferred Pipe Entrance - K = 0.25

K-values for Pipe Exits

When a fluid exits a pipe into a much large body of the same fluid the velocity is reduced to zero and all of the kinetic energy is dissipated, thus the losses in the system are one velocity head regardless of the exit geometry.

Type Shape r/D K-value
All Geometries - - K = 1.0


Further Reading

  1. Piping Calculations Manual (McGraw-Hill Calculations)
  2. Piping Systems Manual
  3. Flow of Fluids Through Valves, Fittings, and Pipe (TP-410 (US edition))