Question

Hydraulics

Problem 4 (25 points) Water flows through a cast iron pipe at 1.2 2.5[km) long with an elevation drop of 50[m]. . The pipe has a diameter 0.6[m] and is 1. Ignoring minor losses, calculate the pressure head drop per unit length over the course of the pipe. Write the equation(s) needed to compute the pressure drop per unit length. First, express - only as a function of all the given parameters (you may use several equations if needed, but do not plug in any of the values). Then, compute the value using the given information. 2. Briefly explain why the pressure head is decreasing along the pipe. 3. A number of design changes could be made to reduce the pressure head drop along the length of the pipe. List at least two such design changes and explain how they would affect the system.

Answer 1

Ginen Discharge through Cast iron pipe = 1.2 m/s Diameter = 0.6m. length (y = 2.5km. Elevation drop al = som. Let us assume the data, Dynamic viscosity of water l = 8.9x10 Pas Roughness height of cast iren pipe K.= 0.35mm 1) we know Q = Av. S VE À I (04) v 1.2 * = 4.Quumls| Reynolds number Rea evde Re - looox 4.244x 0.6 8.9x10-4 Re : 2861912.06

Re> 2000 1 . It is a turbulent flow. pipe friction Coefficient = -d long (0-262) $ abog lase + og 70.262) = -2 67 09 13 260 71-1201310*) on solving f = 0.0149 per unit length Pressure head doop over the course of pipe Pip flv² = 290 - 07 7 - Oz VW Pi-Pa 7 (0:0l49) (2:5X103) (4.244 2 (9.81)(0.6) لی ۷ pre 6.993m/

2 As we move aor over the course of the pipe the head loss due to friction increase as the length of the pipe increases. Therefore, the pressure head decreases along the pipe . 3) The two such design changes are The material of the pipe can be charged As the material changes it would affects the pipe friction Colfficient. As pipe friction coefficient decreases pressure head also direases. - Diameter of the pipe can be changed. As the diameter increases pressure head decreases.