Minor losses in pipes formula
Practical 3: Friction and Minor Losses in Pipes. The energy required to push water through a pipeline is dissipated as friction pressure loss, in m. In this practical you will investigate the impact of major and minor losses on water flow in pipes. For low velocities, where the flow is laminar, friction loss is caused by viscous shearing between streamlines near the wall of the pipe and the friction factor f is well defined.
For high velocities where the flow is fully turbulent, friction loss is caused by water particles coming into contact with irregularities in the surface of the pipe and friction factor itself is a function of surface roughness.
In most engineering applications, the velocity is less than that required for fully turbulent flow and f is a function of both the viscosity of a boundary layer and the roughness of the pipe surface.Losses in Pipes - Fluid Mechanics & Machineries - Mechanical Engineering
Values of f can be determined experimentally and plotted in dimensionless form against Reynolds Number Re to from a Moody Diagram. Algorithm to find largest and smallest of n numbers losses behave similarly to major losses, where a device with a large k value leads to a high pressure loss.
In general, a very sudden change to the flow path contributes to significant pressure loss. Pressure tappings in the pipes are connected to the pressure gauge for indication of pressure reading. Different types of pipes create different amounts of friction thereby impacting on the flow rate.
The changes in water pressure, through the different pipe types, is measured at the end of the rig. The image above is of the friction loss experimental rig showing the different pipes travelling off of the main yellow down pipe. Please download this excel spreadsheet to obtain data for this experiment.
You will see that for the major losses, each pipe had three different flow rates passed through it. In each case, the pressure was measured upstream and downstream to determine the overall pressure head loss over the length of the pipe.
For the minor losses, a single flow rate was passed through the pipe and the pressure was measured upstream and downstream of several typical objects two valves and an elbow bend. These were all in 25mm galvanised steel pipe. It is important to note that the observed pressure head loss in these cases is due to both the minor loss in the object itself and a small amount of pipe friction. For this reason, you have also been given the length of pipe between the two measurements.
You will need to use an appropriate friction factor from your analysis of 25mm galvanised steel pipe in the first part of the experiment major losses. For all of the calculations in this practical you will need to convert the pressure difference into a head measured in metres:.
Where P 1 and P 2 are respectively the upstream and downstream pressure in Pascals. Then you will compare the absolute roughness k with typical roughness values for each pipe material you can find such values in textbooks or on the internet.
So the observed hf can also be given by the Darcy equation:. Note that it is very common in this experiment for results to be spread out such that the average curve does not pass neatly through all three points. The point where your average curve exits the chart on the right is where you can infer the value of relative roughness.The basic approach to all piping systems is to write the Bernoulli equation between two points, connected by a streamline, where the conditions are known.
For example, between the surface of a reservoir and a pipe outlet. The total head at point 0 must match with the total head at point 1, adjusted for any increase in head due to pumps, losses due to pipe friction and so-called "minor losses" due to entries, exits, fittings, etc. Pump head developed is generally a function of the flow through the system, with head rise decreasing with increasing flow through the pump. Friction losses are a complex function of the system geometry, the fluid properties and the flow rate in the system.
By observation, the head loss is roughly proportional to the square of the flow rate in most engineering flows fully developed, turbulent pipe flow. This observation leads to the Darcy-Weisbach equation for head loss due to friction:. Thus, it is often useful to estimate the relationship as the head being directly proportional to the square of the flow rate to simplify calculations.
Reynolds Number is the fundamental dimensionless group in viscous flow. Velocity times Length Scale divided by Kinematic Viscosity. Relative Roughness relates the height of a typical roughness element to the scale of the flow, represented by the pipe diameter, D.
Pipe Cross-section is important, as deviations from circular cross-section will cause secondary flows that increase the pressure drop. Non-circular pipes and ducts are generally treated by using the hydraulic diameter. For laminar flow, the head loss is proportional to velocity rather than velocity squared, thus the friction factor is inversely proportional to velocity.
The Reynolds number must be based on the hydraulic diameter. Blevins Applied Fluid Dynamics Handbook, tablepp. For turbulent flow, Colebrook found an implicit correlation for the friction factor in round pipes. This correlation converges well in few iterations. Convergence can be optimized by slight under-relaxation. From Q and piping determine Reynolds Number, relative roughness and thus the friction factor. Substitute into the Darcy-Weisbach equation to obtain head loss for the given flow.
Substitute into the Bernoulli equation to find the necessary elevation or pump head. Obtain the allowable head loss from the Bernoulli equation, then start by guessing a friction factor. Calculate the velocity from the Darcy-Weisbach equation. From this velocity and the piping characteristics, calculate Reynolds Number, relative roughness and thus friction factor.
Repeat the calculation with the new friction factor until sufficient convergence is obtained. Although they often account for a major portion of the head loss, especially in process piping, the additional losses due to entries and exits, fittings and valves are traditionally referred to as minor losses.
Minor losses in pipe flow
These losses represent additional energy dissipation in the flow, usually caused by secondary flows induced by curvature or recirculation. The minor losses are any head loss present in addition to the head loss for the same length of straight pipe. Like pipe friction, these losses are roughly proportional to the square of the flow rate. Defining K, the loss coefficient, by. K is the sum of all of the loss coefficients in the length of pipe, each contributing to the overall head loss.
Although K appears to be a constant coefficient, it varies with different flow conditions. Factors affecting the value of K include:. Some very basic information on K values for different fittings is included with these notes and in most introductory fluid mechanics texts. For more detail see e.
Losses in Pipes
Blevins, pp. To calculate losses in piping systems with both pipe friction and minor losses use. The procedures are the same except that the K values may also change as iteration progresses. Why Queen's MME?The losses that occur in pipelines due to bends, elbows, joints, valves, etc. This is a misnomer because in many cases these losses are more important than the losses due to pipe friction, considered in the preceding section.
For all minor losses in turbulent flow, the head loss varies as the square of the velocity. Thus a convenient method of expressing the minor losses in flow is by means of a loss coefficient K. Values of the loss coefficient K for typical situations and fittings is found in standard handbooks. The form of Darcys equation used to calculate minor losses of individual fluid system components is expressed by Equation It is the energy loss due to a fitting per unit weight of fluid.
The minor loss calculation is valid for open channels including partially full culverts as well as closed conduits circular or non-circular flowing full. The minor loss calculation does not check for unreasonable inputs such as negative values.
All values should be entered as positive. Membership Register Login. Copyright Notice. Minor Losses Fluid Flow Equation.The head loss of a pipe, tube or duct system, is the same as that produced in a straight pipe or duct whose length is equal to the pipes of the original systems plus the sum of the equivalent lengths of all the components in the system. This can be expressed as. The major head loss for a single pipe or duct can be expressed as:.
Since the velocity - v - in equation 2 in general is related to the pipe or duct where the component is located, the sum of the minor losses in a pipe or duct can be expressed as:. The minor loss can be calculated by summarizing the minor loss coefficients - and multiplying the sum with the dynamic pressure head.
The total head loss for a single pipe can be calculated by using equation 1 and 3 :. The total head loss in several serial connected pipes can be calculated by adding the total head loss in each pipe or duct. The total head loss can be expressed as:. Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro.
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Minor Head Loss - head loss or pressure loss - due to components as valves, bends, tees and the like in the pipe or duct system. Tag Search en: major minor head pressure loss drop pipe tube duct systems. Privacy We don't collect information from our users. Citation This page can be cited as Engineering ToolBox, Modify access date. Scientific Online Calculator.
Make Shortcut to Home Screen?Post a Comment. Recent Updates. After completing my engineering, i had joined an organization and that organization was in chemical manufacturing business. I was assigned there to analyze one pipe flow problem and to produce the outcome in front of the team leader and i had recalled the concept of head losses in pipe flow at that time to produce the required details.
Today we will see here the head losses in pipe flow. Determination of head losses is very important in pipe flow problems and also in designing of a pumping system. So if you need to calculate the head losses in pipe flow, this post will be a very important key for you. There are two types of head losses in pipe flow system i. Major head loss and Minor head loss. Head loss in pipe flow system due to viscous effect i.
Major Head losses in pipe flow problem will be calculated with the help of Darcy-Weisbach formula as mentioned below and this Darcy-Weisbach formula will be used to calculate the major loss in pipe flow, it does not matter that pipe is horizontal, vertical or on inclined plane.
Friction factor as mentioned above will be determined on the basis of type of flow i. Laminar flow, Transition flow and turbulent flow. We can refer below equations in order to determine the friction factor. As we have discussed above minor head losses are pressure losses in pipe flow system due to various piping components such as valves, fittings, elbows, contractions, enlargement, tees, bends and exits.
Type of Piping Components or Fittings. Minor loss coefficient, K. Tee, Flanged, Dividing Line Flow. Union, Threaded. Elbow, Flanged Regular 90 o.
Elbow, Threaded Regular 90 o.The Darcy-Weisbach equation with the Moody diagram is considered to be the most accurate model for estimating frictional head loss for a steady pipe flow. Since the Darcy-Weisbach equation requires iterative calculation an alternative empirical head loss calculation like the Hazen-Williams equation may be preferred:. Note that the Hazen-Williams formula is empirical and lacks a theoretical basis. The head loss for ft pipe can be calculated as. The calculators below can used to calculate the specific head loss head loss per 1 00 ft m pipe and the actual head loss for the actual length of pipe.
Default values are from the example above. The Hazen-Williams equation is not the only empirical formula available.
MAJOR AND MINOR LOSSES IN PIPES
Manning's formula is commonly used to calculate gravity driven flows in open channels. The Hazen-Williams equation is assumed to be relatively accurate for water flow in piping systems when. For hotter water with lower kinematic viscosity example 0. Since the Hazen-Williams method is only valid for water flow - the Darcy Weisbach method should be used for other liquids or gases.
Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro. We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.
Online Hazens-Williams Calculator Imperial Units The calculators below can used to calculate the specific head loss head loss per 1 00 ft m pipe and the actual head loss for the actual length of pipe. Tag Search en: hazen-williams equation. Privacy We don't collect information from our users. Citation This page can be cited as Engineering ToolBox, Modify access date.
Practical 3: Friction and Minor Losses in Pipes
Scientific Online Calculator.Minor losses in pipe flow are a major part in calculating the flow, pressure, or energy reduction in piping systems.
Liquid moving through pipes carries momentum and energy due to the forces acting upon it such as pressure and gravity. Just as certain aspects of the system can increase the fluids energy, there are components of the system that act against the fluid and reduce its energy, velocity, or momentum. Friction and minor losses in pipes are major contributing factors. The kinetic energy factor is used to calculate the configurational head loss, the energy loss to the components of the system.
Before being able to use the minor head losses in an equation, the losses in the system due to friction must also be calculated. After both minor losses and friction losses have been calculated, these values can be summed to find the total head loss. Once calculated, the total head loss can be used to solve the Bernoulli Equation and find unknown values of the system.
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