Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers

Reviewed by Raghvendra Gopal
Last updated: March 30, 2023

## What Does Head Loss Mean?

Head loss is the reduction in head, or pressure, that occurs as fluid flows through a pipe or other hydraulic system due to friction, turbulence or other factors. It is a measure of the energy loss in a fluid system and is typically reported in units of length, such as feet or meters. Head loss is virtually impossible to avoid in real moving fluids; it occurs due to friction between fluid particles moving relative to one another, especially in turbulent flow.

Although head loss means a loss of energy, it does not mean a loss of the fluid's total energy. The fluid's total energy is conserved due to the law of conservation of energy.

Head loss depends on the on a fluid's flow velocity, pipe diameter, pipe length and a friction factor based on the roughness of the pipe and the Reynolds number of the flow.

The term head loss can also be used to describe the energy required to overcome the friction caused by the pipe walls and other technological equipment.

Head loss is an important factor in the design and operation of fluid systems, such as pipelines, pumps and heat exchangers. It represents the amount of energy lost as fluid flows through a system and can have a significant impact on system performance and efficiency.

The head loss in a fluid system is typically calculated using the Darcy-Weisbach equation, which relates the head loss to the fluid's velocity, the pipe's diameter and the friction factor. The Darcy-Weisbach equation is expressed thusly:

hL = f (L/D) (V^2/2g)

Where:

• "hL" is the head loss.
• "f" is the friction factor
• "L" is the length of the pipe.
• "D" is the diameter of the pipe.
• "V" is the velocity of the fluid.
• "g" is the acceleration due to gravity.

The friction factor depends on the Reynolds number of the flow, which is a dimensionless parameter that describes the nature of the flow, whether it is laminar or turbulent. For laminar flow, the friction factor is expressed as:

f = 64/Re

Where "Re" is the Reynolds number.

or turbulent flow, the friction factor is determined using empirical correlations based on experimental data.

Head loss is an important factor in the design of pumps, which are used to transport fluids through pipelines and other conduits. The head loss in a pipeline or other conduit determines the amount of pressure a pump must generate to maintain a desired flow rate. If the head loss is too high, the pump must work harder, which can lead to increased energy consumption and decreased efficiency.

Head loss is also important in the design of heat exchangers, which are used to transfer heat between fluids. The head loss in a heat exchanger can affect the overall performance of the system, including the efficiency of the heat transfer process and the pressure drop across the exchanger.