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How It Works
Minor losses (hL = K × v²/2g) quantify energy lost at fittings, valves, bends, and other flow disturbances in a pipe system. The loss coefficient K is determined experimentally for each fitting type. In compact systems with many fittings, minor losses can exceed friction losses from straight pipe runs.
Example Problem
Water flows at 3 m/s through a fully open globe valve (K = 10). What is the head loss?
- hL = K × v² / (2g) = 10 × 9 / 19.62
- hL = 4.59 m
This is equivalent to the friction loss in roughly 90 m of 50 mm pipe.
Frequently Asked Questions
What is a loss coefficient (K value)?
K is a dimensionless number that quantifies energy loss through a fitting relative to the velocity head. A 90-degree elbow has K ≈ 0.9; a fully open globe valve has K ≈ 10. Higher K means more energy loss.
When do minor losses matter more than friction losses?
In short pipe runs with many fittings, such as building plumbing, HVAC systems, and compact process piping. In long pipelines with few fittings, friction (major) losses dominate.
What is the equivalent length method?
An alternative approach that converts each fitting into an equivalent length of straight pipe. For example, a standard 90-degree elbow might equal 30 pipe diameters of straight pipe. This simplifies total head loss calculations.
Related Calculators
- Darcy-Weisbach Calculator — calculate major (friction) losses along pipe lengths.
- Pump Calculator — size pumps to overcome total head loss including minor losses.
- Bernoulli Theorem Calculator — full energy balance between two points in a system.
- Colebrook Equation Calculator — find the friction factor needed for major and minor loss analysis.
- Pipe Flow Calculator — compute flow rate and velocity for your piping system.
- Pressure Unit Converter — convert head loss between pressure units.