K-factor Method

The excess loss in a fitting is normally expressed in a dimensionless “K” factor. The excess head loss (dH) is less than the total by the amount of frictional loss that would be experienced by straight pipe of the same physical length. The loss coefficient Kf , depends on the Reynolds number of the flow. The values of Kf at low Re can be significantly greater than those at high Re. Additionally, valves and fittings do not scale exactly. e.g., the loss coefficient for a 1/4 in. valve is not the same as that for a 4 in. valve.