What is pressure drop in a pipe? Pressure drop is the decrease in pressure that occurs as fluids flow through pipes due to friction and other factors. When we choose and use various flowmeters, we may all hear the parameter of pressure loss or pressure drop.

It’s important to know how to calculate pressure drop in pipes, as it can help you troubleshoot issues, optimize your system’s performance. In this blog, we’ll show you how to calculate pressure drop in pipes and provide tips to minimize it in your system. Let’s dive in!

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Calculate Pressure Drop in a Pipe

5 Factors Affecting Pressure Drop

In industrial settings, pipes are often used to transport liquids, gases, and other materials over long distances. When fluids flow through pipes, they experience pressure drop due to various factors, which can affect the efficiency of the system and even cause equipment failure.

In an industrial pipe system, several factors contribute to pressure drop, including the flow rate, pipe diameter, pipe length, fluid properties (like density and viscosity). And the presence of fittings and valves. These factors must be carefully considered when designing or troubleshooting an industrial pipe system to ensure that it operates safely, efficiently, and reliably.

In this section, we’ll explore each of these factors in more detail and discuss their impact on pressure drop in industrial pipes.

Flow rate is one of the key factors that affects pressure drop in a pipe.

In simple terms, flow rate refers to the volume or mass of fluid that flows through a pipe per unit time. Typically measured in gallons per minute (GPM) or liters per second (L/s). The higher the flow rate, the greater the pressure drop in the pipe due to friction and other factors.

As the fluid flows through the pipe, it interacts with the walls of the pipe and experiences frictional resistance, which results in a loss of energy and pressure drop.

In addition to frictional resistance, high flow rates can also cause turbulence in the fluid, which further increases pressure drop. Turbulence occurs when the fluid flow becomes irregular and chaotic, causing eddies and vortices that can further reduce the fluid’s energy and increase pressure drop.

The National Institute of Standards and Technology (NIST) provides a comprehensive guide to fluid flow in pipes that includes equations and data for calculating pressure drop.

According to the NIST guide, the pressure drop in a pipe is directly proportional to the flow rate raised to the power of 1.75. This means that as the flow rate increases, the pressure drop increases at a faster rate.

The NIST guide is available on the official website of the U.S. Department of Commerce.

The diameter of a pipe is a crucial factor that affects pressure loss in pipelines. Generally, smaller pipes have higher pressure losses than larger pipes.

This is due to the relatively greater surface area of smaller pipes, which results in higher frictional losses and turbulence in the fluid.

Additionally, smaller pipes are more prone to blockages or obstructions, which can further increase pressure loss.

To illustrate the impact of pipe diameter on pressure loss, researchers often use the Darcy-Weisbach equation, which relates pressure loss to pipe diameter, fluid density, fluid velocity, and other variables.

According to this equation, pressure loss is proportional to the length of the pipe, the fluid viscosity, and the square of the fluid velocity. But inversely proportional to the diameter of the pipe raised to the power of 5.

For example, if the diameter of a pipe is doubled, the pressure loss is reduced by a factor of 32. This demonstrates the importance of selecting the appropriate pipe diameter for a given system to minimize pressure loss and optimize system performance.

The length of a pipe is another crucial factor that affects pressure loss in pipelines.

Generally, longer pipes have higher pressure losses than shorter pipes. This is due to the relatively greater surface area and more frictional losses in longer pipes.

Additionally, longer pipes are more prone to blockages or obstructions, which can further increase pressure loss.

The Darcy-Weisbach equation, which relates pressure loss to pipe length, fluid density, fluid velocity, and other variables. According to this equation, pressure loss is proportional to the length of the pipe, the fluid viscosity, and the square of the fluid velocity, but inversely proportional to the diameter of the pipe raised to the power of 5.

For example, if the length of a pipe is doubled, the pressure loss is also doubled. This demonstrates the importance of minimizing the length of pipelines and selecting the appropriate pipe diameter for a given system to minimize pressure loss and optimize system performance.

The fluid properties, including density and viscosity, are important factors affecting pipeline pressure loss. As the fluid density and viscosity increase, the pressure loss in the pipe also increases.

This is due to the increased friction between the fluid and the pipe walls, resulting in a greater loss of energy as the fluid flows through the pipe.

According to a study published in the Journal of Energy, the effect of fluid density on pipeline pressure loss can be significant. Increasing the fluid density from 1 kg/m³ to 1000 kg/m³ resulted in a 30% increase in pressure drop.

Another study published in the Journal of Petroleum Science and Engineering showed that the effect of fluid viscosity on pipeline pressure loss is even more significant. Increasing the fluid viscosity from 1 cP to 100 cP resulted in a 270% increase in pressure drop.

In addition to pipe diameter, length, and fluid properties, the fittings and valves used in a pipeline also affect the pressure loss. Fittings and valves cause additional turbulence in the fluid flow, leading to increased friction and pressure loss.

According to a report published by the National Institute of Standards and Technology (NIST), the pressure loss in a pipeline due to fittings and valves can range from 10% to over 50% of the total pressure drop, depending on the type and number of fittings and valves used.

Read more about: Shop 101: Key Factors In Selecting A Pipe Flow Meter

Calculation of Pressure Drop

Calculating pressure drop in a pipeline involves several steps, including:

  • Determine the flow rate of the fluid in the pipeline.
  • Determine the properties of the fluid, such as density and viscosity.
  • Measure the pipe length, diameter, and roughness.
  • Determine the number and type of fittings and valves in the pipeline.
  • Select the appropriate pressure drop equation based on the specific pipeline conditions and design.
  • Calculate the Reynolds number to determine if the flow is laminar or turbulent.
  • Use the selected pressure drop equation to calculate the pressure drop.
  • Compare the calculated pressure drop with the maximum allowable pressure drop to ensure that the pipeline operates safely.

It’s important to note that pressure drop calculations may need to be repeated several times to ensure that the pipeline design meets the required pressure and flow rate specifications. It’s also important to ensure that accurate and up-to-date data is used in the calculation to ensure the safety and efficiency of the pipeline.

Pressure Drop Equations

Pressure drop equations are mathematical formulas that engineers and designers use to calculate the pressure loss in a pipeline. There are many different equations, but three of the most common are Bernoulli’s equation, the Darcy-Weisbach equation, and the Hazen-Williams equation.

  • Bernoulli’s equation
  • Darcy-Weisbach equation
  • Hazen-Williams equation

For a detailed introduction to the equation, please refer to the professional academic website. There are detailed discussions. We will not repeat them here.

Read more about: Flow Rate And Pressure Relationship

Online Pressure Drop Calculators and Software

Online pressure drop calculators and software have made it easier than ever to calculate the pressure drop in a pipeline. These tools provide users with an easy and efficient way to input pipeline data and receive accurate pressure drop calculations.

Online calculators typically require the user to input pipeline data such as flow rate, pipe diameter, length, fluid density and viscosity, and fittings and valve information. The software then uses algorithms and equations to provide an estimate of the pressure drop in the pipeline.

These tools are particularly useful for engineers, technicians, and operators who need to quickly and accurately calculate pressure drops for a wide range of pipeline applications.

For example: Pressure Drop Online-Calculator

Flow Meter Pressure Drop

Flow Meter Pressure Drop, also known as Pressure loss, is one of the key indicators of flow meters.

Flow Meter Pressure Drop is used to describe the pressure difference (P1-P2) before and after the flow meter input (P1) and output (P2). It is also the minimum pressure difference to ensure the normal operation of the flowmeter. It is one of the basic parameters of the flowmeter.

The pressure loss of the flowmeter generally increases with the increase of the flow rate. Also affected by the solution. For example, the pressure loss of flowmeters based on ultrasonic flowmeters and MEMS (micro-electromechanical systems) is much smaller than that of vortex flowmeters and differential pressure flowmeters.

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So is there any flowmeter that does not cause pipeline pressure loss?
Yes. Ultrasonic flowmeter, clamp-on sensor, does not need to cut the pipeline, and will not affect the pressure of the pipeline.

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Understanding the Pressure Drop of the pipeline helps us to design the pipeline system reasonably.

The Pressure Drop of the flowmeter is also an important parameter to consider. The pressure loss of the flowmeter will cause energy consumption, which is an important parameter to characterize the performance of the flowmeter. It is also more and more people’s attention and become one of the important indicators of flow meter selection.

Sino-Inst is a manufacturer of flow meters. If users have technical questions about the Pressure Drop of the flowmeter, they can contact our sales engineers at any time.

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