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Unformatted text preview: APPLICATION I: STEADY PIPE FLOW IN SIMPLE PIPELINES M.S. Ghidaoui (CIVL 252, Spring 2001) Pipeline systems are used to: 1. Transport water from where it is available to where it is needed: water supply; seawater for flushing etc. 2. Dispose treated water into assimilative water bodies such as the ocean. 3. Convey sewage from sources to treatment plants. 4. Drain rain water (storm-water) from urban areas. 5. Transport oil and gas. 6. Conveyance of various chemicals in chemical plants. 7. Transport blood in living bodies (veins are pipes; blood is the fluid; heart is the pump!). 8. Supply fuel from reservoirs to engines in cars, planes etc. The above cited examples are by no means exhaustive. Try to think of more examples yourself. A modern water supply system often comprises: 1. A water source: In Hong Kong, about 80% of our water comes from Guangdong, China, and about 20% from local natural rainfall catchment. We expect to pay for 840 million cubic metres to Guangdong in the year 2000. Assuming 7 million inhabitants, then we are buying about 330 litres per capita (person) per day! 2. Pipes: In Hong Kong, the freshwater pipes add up to a total length of 2245 about 5000km (i.e., roughly the earth’s radius!) 3. Pumps: The number of pumping stations for freshwater in Hong Kong is 2245 145. Pumps provide flexibility to vary flowrates and pressures; overcome energy losses through the pipeline system and deliver water against gravity. 4. Impounding reservoirs : main water supply reservoirs (e.g., High Island reservoir; Plover Cove reservoir etc.). There are 17 such reservoirs in Hong Kong. 5. Service reservoirs : located within the distribution system. There are 167 fresh water service reservoirs in Hong Kong. They provide quick response to water needs and storage capacity for low demand periods during the day and at night. 6. Control devices: to control the magnitudes of high and low pressures which are generated either during steady or unsteady (surge or waterhammer events) flow conditions. Example of control devices: surge tanks, air chambers, pressure relief valves, air valves etc. 7. Check valves: Allows flow in one direction only. Mainly used in the vicinity of pumps. 8. Pressure relief valves (PRV) : maintains a constant pressure downstream of it regardless of how large the upstream pressure becomes. Function of valves : control flow and pressure through the pipeline system. Some typical control valves are given the figure below. For data related to freshwater and flushing water supply systems in Hong Kong and for a figures of typical distribution systems in Hong Kong you may consult the web page of the water supply department (WSD): http :// ....
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