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The Hazen–Williams equation is an empirical relationship that 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 [ 1 ] such as fire sprinkler systems , [ 2 ] water supply networks , and irrigation systems.
The Hardy Cross method can be used to calculate the flow distribution in a pipe network. Consider the example of a simple pipe flow network shown at the right. For this example, the in and out flows will be 10 liters per second. We will consider n to be 2, and the head loss per unit flow r, and initial flow guess for each pipe as follows:
Generally the head losses (potential differences) at each node are neglected, and a solution is sought for the steady-state flows on the network, taking into account the pipe specifications (lengths and diameters), pipe friction properties and known flow rates or head losses. The steady-state flows on the network must satisfy two conditions:
The probable intensity and extent of a fire inside the building are indicated by factors including the building use, the building height, the items contained inside the building and their arrangement. These variables are compared to tables and values expressed in the model codes. The values in these tables are based on fire tests and loss history.
Allen Hazen (August 28, 1869 – July 26, 1930) was an American civil engineer and an expert in hydraulics, flood control, water purification and sewage treatment.His career extended from 1888 to 1930, and he is, perhaps, best known for his contributions to hydraulics with the Hazen-Williams equation.
In fluid dynamics, head is a concept that relates the energy in an incompressible fluid to the height of an equivalent static column of that fluid. From Bernoulli's principle, the total energy at a given point in a fluid is the kinetic energy associated with the speed of flow of the fluid, plus energy from static pressure in the fluid, plus energy from the height of the fluid relative to an ...
These three pressures, the static pressure, the stagnation pressure, and the residual pressure, along with a specified design pressure of 20psi taken from the American Water Works Association (AWWA) or the NFPA are input into the Hazen-Williams formula to calculate the available flow for fire protection.
For a fully filled duct or pipe whose cross-section is a convex regular polygon, the hydraulic diameter is equivalent to the diameter of a circle inscribed within the wetted perimeter. This can be seen as follows: The N {\displaystyle N} -sided regular polygon is a union of N {\displaystyle N} triangles, each of height D / 2 {\displaystyle D/2 ...