The Hazen-Williams equation for calculating head loss in pipes and tubes due to friction can be expressed as:. The Hazen-Williams equation estimates an accurate head loss due to friction for fluids with a kinematic viscosity of approximately 1. More about fluids and kinematic viscosity. The results is acceptable for cold water at 60 o F For hot water with lower kinematic viscosity 0.
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Sodiki1, Emmanuel M. Adigio2 1. ABSTRACT: The historical development of the common methods of estimating the frictional loss and the loss through pipe fittings in water distribution systems respectively, the Hazen-Williams and DArcy-Weisbach equations are briefly reviewed. Furthermore, the methods of applying these equations to index pipe runs are outlined. The available pressure at any point in a fluid flow conduit is progressively reduced away from the pressure source such as the elevated storage, or the pump, in a water distribution system due to frictional losses through conduit fittings such as elbows, tees and reducers and valves.
Thus, the determination of the required source pressure requires the calculation of the system loss components. This paper outlines the historical development and application of the common methods of estimating the head loss components in water distribution systems. The equations for calculating the head loss components in water distribution systems, namely the friction loss and the loss through pipe fittings are discussed as follows: Frictional Loss : The empirical Prony equation Wikipedia, b was the most widely used equation in the 19th century.
Later empirical developments brought about the D Arcy Weisbach equation DArcy, ; Weisbach, ; Brown, ; Haktanir and Ardiclioglu, which is considered more accurate than several other methods of calculating the frictional head loss in steady flow by many engineers Giles, ; Douglas et al, ; Walski,. For all pipes, many engineers consider the Colebrook-White equation Colebrook and White, ; Keady, ; Schroeder, ; Douglas et al, more reliable in evaluating f.
The equation is. Equation 7 is difficult to solve as appears on both sides of the equation. Typically, it is solved by iterating through assumed values of until both sided become equal.
The hydraulic analysis of pipelines and water distribution systems, using the equation, often involves the implementation of a tedious and timeconsuming iterative procedure that requires the extensive use of computers. Empirical head loss equations have a long and honorable history of use in pipeline problems. The use of such empirical equations preceded by decades the development of the Moody diagram Moody, which gives the relation between , Re and relative roughness.
Another of such developments are the Hunter Curves due to Hunter Rouse, The Moody diagram and old empirical equations are still commonly used today. Also, the flow rate subsumes the velocity of Eqn. It had been noted that C-values obtained from different sources have some differences due to the differing experimental conditions Keller and Bliesner, Applying Eqn. The use of the Hazen-Williams formula avoids the use of Eqn. Also, Usman et al, had noted: it is easier to apply the Hazen-William formula than to obtain f from the Colebrook-White equation and then utilizing in the DArcy -Weisbach equation to obtain the frictional loss.
The Hazen-Williams formula is also accurate over a wide range of Reynolds numbers. Graphical presentations of the form of Eqn. One of such graphs is shown in Fig. Also, nomograms which represent Eqn. Furthermore, can derived model equations for calculating friction head losses in some commercial pipe materials by first creating a dimensional grid of 25 pipe diameters selected in equal increments in the interval of 0.
The values, so obtained, were then applied in the DArcy Weisbach equation to obtain a set of head loss values. Values of which are empirically determined are usually listed in tabular form such as Table 2 Giles, Graphical presentations are also common Hydraulic Institute, ; Heald, Furthermore, several correlations had been done to obtain equations useful in predicting losses in pipe fittings Hooper, ; Crane Co.
It has been observed that -values obtained from different sources have some differences due to the differing empirical conditions Ding et al, ; Muklis, Furthermore, experiments performed at the Department of Mechanical Engineering of Indian Institute of Technology, Bombay had shown variations of with the flow Reynolds number, Re www. Variations of with size of fitting had also been observed Rahimi, Thus, the -value for a particular fitting is not universally constant.
It is, however, useful for arriving at a reasonable estimate of the head loss through the pipe fitting. An alternative method of estimating head loss through fittings uses the concept of equivalent length of pipe which would result in the same frictional loss as the loss through the fitting Muklis, ; www.
By this concept, the appropriate form of Eqn. Hence, the total loss frictional and through the fitting in a given pipe section is Values of. Their application in the analysis of index pipe runs has also been discussed.
Table 2: Typical K values through common fittings Pipe fitting 45o bend o. Barry, R. Learn more about Scribd Membership Home. Much more than documents.
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Report this Document. Flag for Inappropriate Content. Download Now. Related titles. Carousel Previous Carousel Next. Jump to Page. Search inside document. Later empirical developments brought about the D Arcy Weisbach equation DArcy, ; Weisbach, ; Brown, ; Haktanir and Ardiclioglu, which is considered more accurate than several other methods of calculating the frictional head loss in steady flow by many engineers Giles, ; Douglas et al, ; Walski, www.
The equation is Equation 7 is difficult to solve as appears on both sides of the equation. Hence, the total loss frictional and through the fitting in a given pipe section is Values of for common types of fitting are as listed in Table 3 Barry, Mohd Nawi Salleh. Harmanpreet Singh Randhawa. Fahmi Adha Nurdin. Joaquin Fuentes. Lata Deshmukh. Ali Ymcmb. Nor Farah Alwani. Dharmendra Jain. Ay Ch. Sen Hu. Sujit Rajan. Smai Debbarma. Miguel Antonio Francisco Reyes.
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Ecuación de Hazen-williams (Caída de Presión)
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.
The Hazen—Williams equation is an empirical relationship which relates the flow of water in a pipe with the physical properties of the pipe and the pressure drop caused by friction. It is used in the design of water pipe systems  such as fire sprinkler systems ,  water supply networks , and irrigation systems. The Hazen—Williams equation has the advantage that the coefficient C is not a function of the Reynolds number , but it has the disadvantage that it is only valid for water. Also, it does not account for the temperature or viscosity of the water. Henri Pitot discovered that the velocity of a fluid was proportional to the square root of its head in the early 18th century. The variable C expresses the proportionality, but the value of C is not a constant.