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Hazen-Williams equation, flow velocity calculation

작성자 Uploader : ezcivil 작성일 Upload Date: 2016-05-10변경일 Update Date: 2016-05-10조회수 View : 906

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. It is named after Allen Hazen and Gardner Stewart Williams.

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.

V = k * C * R^0.63 * S^0.54
V : flow velocity (m/s)
k : a conversion factor for the unit system
(k = 1.318 for US customary units, k = 0.849 for SI units)
C : a roughness coefficient
R : the hydraulic radius (m)
S : the slope of the energy line (head loss per length of pipe or hf/L)

Material / C Factor low / C Factor high
------------------------------------------
Asbestos-cement / 140 / 140
Cast iron new / 130 / 130
Cast iron 10 years / 107 / 113
Cast iron 20 years / 89 / 100
Cast iron 30 years / 75 / 90
Cast iron 40 years / 64 / 83
Cement-Mortar Lined Ductile Iron Pipe / 140 / 140
Concrete / 100 / 140
Copper / 130 / 140
Steel / 90 / 110
Galvanized iron / 120 / 120
Polyethylene / 140 / 140
Polyvinyl chloride (PVC) / 150 / 150
Fibre-reinforced plastic (FRP) / 150 / 150

*** 참고문헌[References] ***

https://en.wikipedia.org/wiki/Hazen%E2%80%93Williams_equation

V = k * C * R^0.63 * S^0.54


변수명 Variable	변수값 Value	변 수 설 명 Description of the variable

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Hazen-Williams equation, flow velocity calculation

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