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A hydropneumatic elevator consists of a piston-cylinder assembly to lift the elevator cab. Hydraulic oil, stored in an accumulator tank pressurized by air, is valved to the piston as needed to lift the elevator. When the elevator descends, oil is returned to the accumulator. Design the least expensive accumulator that can satisfy the system requirements. Assume the lift is 3 floors, the maximum load is 10 passengers, and the maximum system pressure is 800 kPa gage. For column bending strength, the piston diameter must be at least 150 mm. The elevator cab and piston have a combined mass of 3000 kg, and are to be purchased. Perform the analysis needed to define, as a function of system operating pressure, the piston diameter, the accumulator volume and diameter, and the wall thickness. Discuss safety features that your company should specify for the complete elevator system. Would it be preferable to use a completely pneumatic design or a completely hydraulic design? Why?
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Fox And Mcdonald's Introduction To Fluid Mechanics
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- 4. Working for an engineering consultancy firm, your knowledge of fluid dynamics is required to design a new safety feature for a high-pressure air line in a factory. The air line takes the form of a cylindrical pipe of diameter 150 mm, which is designed to operate between 0.45 MPa and 0.76 MPa. At the end of the pipe a bursting disk is placed so that, if the pressure exceeds the maximum operating pressure, the air is vented to atmosphere rather than over-pressuring the chemical reaction vessel (Figures 4a and 4b). In this question, you should treat the flow as quasi- one-dimensional and inviscid. The air in the surrounding atmosphere is at 101 kPa and 298 K. a) You have a choice of five disks which can withstand the following forces across them before bursting: 10.5 kN, 11.0 kN, 11.5 kN, 12.0 kN, 12.5 kN. Which of these bursting disks would you recommend, and why? b) Due to an over-pressurisation of the air line, the disk bursts at time t = 0. At what pressure in the air line will…arrow_forward1-If the combination of pump and motor is 80% efficient, how much electrical power (kW) is needed to drive the pump? 2• If, in order to avoid vapour lock, the pressure in the pipeline must always be above the vapor pressure of the crude oil, what is the maximum permissible elevation of point 3 relative to point 4? 3• If the flow in the pipeline were at the upper limit of being laminar, what pump exit pressure would then be needed? (Answer this part without using the friction factor plot.arrow_forward5. Oil of specific gravity 0.750 is pumped from a tank over a hill through a 24′′ pipe with the pressure at the top of the hill maintained at 25.5 psi. The summit is 250 ft above the surface of the oil in the tank, and oil is pumped at the rate of 22.0 cfs. If the lost head from tank to summit is 15.7 ft, what horsepower must the pump supply to the liquid? indicate free body diagramarrow_forward
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