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Friction Loss Calculator

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What is friction loss?How to calculate friction lossHazen-Williams equationUsing the pipe friction loss calculatorExample: Using the friction loss calculatorFAQs

The friction loss calculator helps you to calculate the amount of pressure head loss due to friction for a given dimension of pipe and volumetric flow rate. The fluid flow inside a pipe or conduit is affected by friction, just like while pushing a heavy box on a rough surface. The friction force arising due to the interaction of fluids with the pipe walls causes a loss in energy. The pipe friction calculator utilizes the Hazen-Williams formula to calculate friction loss.

Furthermore, you can estimate the loss in pressure due to friction using our tool, meaning this pipe friction calculator can find the pressure drop in a water pipe system. Common examples of water pipe systems are the water supply to your kitchen, the sprinkler system on the roof, water in a fire hose, and a piping system to fill your swimming pool.

The water flow in the mentioned systems has varied efficiency and pressure output depending on factors like friction due to the pipe's material. Every material contributes differently to friction loss, e.g., friction loss in a fire hose will vary from friction loss in pipe fittings. In the subsequent sections, we will find out about the variation in friction head loss pressure due to a change in material.

What is friction loss?

When a fluid passes through a conduit or pipe, the roughness of the internal pipe walls and the fluid's viscosity affects the fluid flow, causing a loss in energy or pressure. This pressure loss affects the efficiency of pumping machines, as well as the output at the outlet. Engineers estimate this loss based on the pipes used in the system to get the desired water flow energy output.

How to calculate friction loss

There are several ways to calculate the friction loss in pipe fittings, such as the Darcy-Weisbach formula, Hagen-Poiseuille's law, and the Hazen-Williams friction loss formula. Each formulation has its merits and demerits: we met them at three dedicated calculators: the Darcy-Weisbach calculator, the Poiseuille's law calculator, and the pipe flow calculator. For instance, the Hagen-Poiseuille's Law utilizes the dynamic viscosity and falls short in low fluid viscosity conditions and in wide pipes due to turbulent water flow from the increase in Reynold's number. Learn more about the effects of this single important number at our Reynolds number calculator.

This led researchers to move towards more complex models like the Darcy-Weisbach formula. However, despite being universally applicable and highly accurate, the friction factor term in the Darcy-Weisbach formula is difficult to estimate and has to be supplemented by the Moody diagram. The Moody diagram also relies on Reynold's number to estimate the friction factor. Lastly, the Hazen-Williams equation was pitched as a simpler version to estimate the pipe friction losses. The equation, however, is limited to water as the fluid medium.

Hazen-Williams equation

The friction head loss, HLH_\mathrm{L}, can be estimated by the empirical Hazen-Williams friction loss formula using the pipe dimensions — Length, LL , diameter, DD, volumetric flow rate, QQ, and the roughness coefficient, CC, as:

HL=10.67LQ1.852C1.852D4.87H_\mathrm{L} = \frac{10.67\cdot L \cdot Q^{1.852}}{C^{1.852}\cdot D^{4.87}}

Alternatively, the equation in its Imperial units form is:

HL=4.52LQ1.852C1.852D4.87H_\mathrm{L} = \frac{4.52 \cdot L \cdot Q^{1.852}}{C^{1.852}\cdot D^{4.87}}

Furthermore, the pressure drop, PdP_\mathrm{d}, can be estimated from head loss, HLH_\mathrm{L}, using the specific weight of water, WW as:

Pd=HLWP_\mathrm{d} = H_\mathrm{L} \cdot W

Using the pipe friction loss calculator

Follow the steps below to estimate the friction head loss:

  1. Enter the dimensions of the pipe i.e. diameter, DD, and length, LL.

  2. Input the volumetric flow rate, QQ.

  3. You can pick the pipe material, which will provide its respective roughness coefficient, CC.

    Alternatively, select custom as the material and manually enter a custom pipe roughness coefficient.

  4. The pipe friction calculator will return friction loss for the pipe system.

You can also change the materials for the same dimensions and volumetric flow rates to note the difference between pressure loss and observe the performance of different pipe materials. See below for an example problem.

🙋 You may also find our Poise-Stokes converter useful when dealing with these problems: give it a try!

Example: Using the friction loss calculator

Estimate the loss in pressure due to friction for a copper pipe with diameter 250 mm250\ \mathrm{mm} and length 10 m10\ \mathrm{m} if the volumetric flow rate is 0.5 m3/s0.5\ \mathrm{m^3/s}.Take specific weight of water, WW, as 9810 N/m39810\ \mathrm{N/m^3}.

This gives D=250 mm=0.25 mD = 250\ \mathrm{mm} = 0.25\ \mathrm{m}, L=10 mL = 10\ \mathrm{m}, and Q=0.5 m3/sQ = 0.5\ \mathrm{m^3/s}.

For the material, a copper pipe, C=135C = 135.

HL=10.67×10×(0.5135)1.8520.254.87=2.868 m\begin{split} H_\mathrm{L}&=\frac{10.67 \times 10 \times \left(\frac{0.5}{135}\right)^{1.852}}{0.25^{4.87}}\\[1em] &=2.868\ \mathrm{m} \end{split}

The pressure drop, PdP_\mathrm{d}, can be estimated as:

Pd=2.868×9810=28135.08 N/m2=0.28 bar\begin{split} P_\mathrm{d}&= 2.868 \times 9810\\ &= 28135.08\ \mathrm{N/m^2}\\ &= 0.28\ \mathrm{bar} \end{split}

This implies the pressure drop in the flow due to pipe friction is 0.28 bar0.28\ \mathrm{bar}. Now, let's compare this with a different pipe material, say a fiberglass (FRP) pipe.

For fiberglass, C=150C = 150. Therefore,

HL=10.67×10×(0.5150)1.8520.254.87=2.3594 m\begin{split} H_\mathrm{L}&=\frac{10.67 \times 10 \times \left(\frac{0.5}{150}\right)^{1.852}}{0.25^{4.87}}\\[1em] &=2.3594\ \mathrm{m} \end{split}

of water.

The pressure drop, PdP_\mathrm{d}, can be estimated as:

Pd=2.3594×9810=23145.714 N/m2=0.23 bar\begin{split} P_\mathrm{d} &= 2.3594 \times 9810\\ &= 23145.714\ \mathrm{N/m^2}\\ &= 0.23\ \mathrm{bar} \end{split}

We observed that the pressure loss due to friction is higher in copper pipes compared to fiberglass pipes.


What does friction in a pipe cause?

Friction in a pipe flow results in loss of fluid pressure. This will lead to inefficiency in the pumping machine and loss of pressure at the outlet. You can calculate this pressure loss using our friction loss calculator.

How do I calculate frictional losses in a pipe?

To calculate the frictional head loss in a pipe using the Hazen-Williams equation, follow these steps:

  1. Multiply the length of the pipe L with the volumetric flow rate Q raised to the power 1.852.

  2. Divide this by the pipe diameter D raised to the power 4.87.

  3. Divide this by pipe roughness coefficient C raised to the power 1.852.

  4. If all dimensions are in metric units, multiply the result from Step 3 by 10.67 to get the frictional head loss. If you're using imperial units, multiply by 4.52 instead.

  5. Alternatively, use our frictional loss calculator!

What are the 3 methods to calculate friction loss of water in pipe flow?

The three methods we can use to calculate the frictional loss in water flowing in a pipe are:

  1. Hagen–Poiseuille method.
  2. Darcy-Weisbach method.
  3. Hazen-Williams method.

What are the four factors that affect friction loss in pipes?

The four main factors affecting the frictional loss in a pipe are:

  • The pipe's diameter;
  • The length of the pipe;
  • The pipe's roughness factor; and
  • The volumetric flow rate.

Apart from these, the fluid's viscosity and the elevation difference between the inlet and the outlet may also need to be considered.

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