Homework of Chapter (4.2,4.3)

Transcription

1 Dead Line: Saturday (24/3/2018) The Islamic University of Gaza, Instructors: Dr. Khalil M. Al Astal Civil Engineering Department, Hydraulics -Discussion, Second semester, T.A: Eng. Mohammed AbuRahma T.A: Eng. Reem Sbaih Homework of Chapter (4.2,4.3) Solve the following Problems (Networks): Problem An industrial water-distribution system is schematically shown in Figure P The demands on the system are currently at junctions D (0.550 m 3 /sec) and E (0.450 m 3 /sec). Water enters the system at junction A from a storage tank (surface elevation of m). All pipes are concrete (e = 0.36 mm) with lengths and diameters provided in the table below. In addition, the elevations of the junctions are given in the table below. Calculate the flow rate in each pipe (initial estimated flows are provided). Also determine if the pressure at each junction exceeds 185 kpa, a requirement of the water company by the industrial park. (using hardy cross method and do 2 iterations) 1

2 Problem A three-loop water-distribution system is depicted in Figure P The demands on the system are currently at junctions C (6.00 cfs), D (8.00 cfs) and E (11.0 cfs). Water enters the system at junction A from a storage tank with a pressure of 45 psi. Using the pipe network data in the table below, calculate the flow rate in each pipe (initial estimated flows are provided). Also determine the water pressure at each junction (30 psi is required by the customers). Pipe network analysis software would be useful. (using hardy cross method and do 2 iterations) 2

3 300m D=0.1 m D=0.3 m Additional problems: Problem (1) Neglecting minor losses, determine: 1. The flow through each pipe. 2. The pressure head at node F. Use the following data: Friction factor, f = 0.02, for all pipes. Pressure head at node A = 70 m. Perform only one iteration of Hardy cross method (Assume initially that QEH = 50 L/s) Node A B C D E F G H Elevation (m) above datum L/s Qin A D=0.5 m B 500m D=0.4 m D C 20 L/s H E G F 3

4 Problem (2) Neglecting minor losses, use Hardy-Cross method to determine the flow rate through each pipe for the following cases: 1. if the gate valve is closed. 2. if the gate valve is fully opened. Use the following data: All pipes are 600m long and 400 mm in diameter, with a friction factor f =0.02 Do only one iteration (stop after you correct Q) In the initial flow assumption, divide the flow equally between the pipes. B 0.6 m 3 /s A Gate valve C D 4

5 Solve the following Problems (Water Hammer): Problem A horizontal pipe 30 cm in diameter and 420 m long has a wall thickness of 1 cm. The pipe is commercial steel and carries water from a reservoir to a level 100 m below and discharges into the air. A rotary valve is installed at the downstream end. Calculate the maximum water hammer pressure that can be expected on the valve if it closes in a 0.5-sec period (neglect longitudinal stresses). Also determine the total (maximum) pressure the pipeline will be exposed to during the water hammer phenomenon. Problem A 500-m long pipeline carries oil (sp. gr. = 0.85) from a storage tank to the hold of an oil tanker. The 0.5-m-diameter steel pipe has expansion joints and a wall thickness of 2.5 cm. The normal discharge rate is 1.45 m 3 /sec, but it can be controlled by a valve at the end of the pipeline. The surface of the oil in the storage tank is 19.5 m above the outlet of the pipe. Determine the maximum valve closure time that would put it into the category of a rapid closure. Problem A 700-m-long, 2.0-m-diameter steel penstock conveys water from a reservoir to a turbine. The reservoir water surface is 150 m above the turbine, and the flow rate is 77.9 m 3 /sec. A gate valve is installed at the downstream end of the pipe. Determine the wall thickness to avoid damage to the pipeline if the gate valve is closed rapidly. Use this equation (PD = 2Te) to determine the allowable pressure the pipe can withstand based on hoop stress theory with T = 1.1 X 10 8 N/m 2. Neglect longitudinal stresses and assume that the operational pressure is minimal compared to the maximum water hammer pressure. 5