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Mechanical Engineering Design

1 The carbon dioxide in a nuclear reactor is maintained at 40 bar (gauge) and 70 deg C. Estimate its density, specific weight and relative density.

2 A water-filled manometer indicates a pressure differential of 2100 N/m2. What is the difference in elevation of the vertical limbs?

3 A vertical plate measuring 1m is exposed to water on one side and to air on the others.
It is held in position by hinges at the bottom and slips at the top. What forces have
to be resisted by hinges and the clips:
a) if the pressure at the top of the gate is atmospheric.
b) if the pressure there is 50 kN/m2?

4 Air flows through a contracting tube, its velocity changing from 15 m/sec to 45 m/sec. In these circumstance the density may taken to be constant at 1.2kg/m3. The diameter of the first section is 30 cm; estimate that of the second section

5 For the case described in question 4, does the pressure rise or fall? Why? What is the pressure change? Why is it reasonable to take the density to be constant?

6 A pipeline of diameter 0.3m carries a teady flow of oil of density 811 kg/m3 at a velocity of 24.4 m/sec. At point A the pressure is 363kPa and the elevation is 30.5m; at point B the pressure is 20 kPa and the elevation 33.5m. What is the change in the energy of the fluid, measured in m, in kPa and in kJ/kg? Is mechanical energy supplied to or extracted from the fluid?

7 An air blower is required to deliver 19 m3/sec. A suction gauge on the inlet side reads 50mm of water, while a gauge on the discharge side gives a positive of 75mm of water. The discharge gauge is attached at a points 2m above the suction gauge; the discharge and inlet pipes are of identical diameter. If an overall efficiency of 68 per cent can be assumed, what motor power is required?

8 The pressure drop along a length of straight horizontal pipe is 4.2 N/m2..The diameter is 10cm and the length 20m. What is the force applied to the fluid at the pipe wall to resist the flow? What is the shear stress at the wall?

9 (a) Water flows from a large high level vented tank to a large low level vented tank via a straight pipe of 15 metre length, 50 mm internal diameter and friction factor f1=0.008 (equivalent to f2 = 0.032). The pipe is flange connected to the side of each tank below the water level. When the difference in water level between the tanks is 10 metre. Calculate the velocity and volume flow ate through the pipe.

(b) If the friction factor f1 (or f2) had not been given in part (a), briefly explain how you would have used a Moody Chart to establish the friction factor for a specified pipe material.

( c ) If it required to pump water from the lower tank to the upper tank at the same rate as the water flowed down under gravitational influence, calculate the required head input to the water by the pump. If the overall pump efficiency is 70%, calculate the power input to the pump.

Solution Summary

The solution examines different mechanical engineering design scenarios.