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PS_30 - NOTE Neglect frictional losses but do not neglect...

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ChBE421 Problem Set #3 Fall 2009 1. A hovercraft is a vehicle which floats on a cushion of air. In a simplified design as illustrated below, the craft has an air intake 7 ft in diameter through which air enters at 72 ft/sec, and p = p ATM . The air discharges at p ATM through a cylindrical surface 16 ft in diameter and 3.5’’ high as illustrated. The pressure underneath the craft is given by p = p ATM + k (1 – r 2 / a 2 ) where k = ½ ρ ∙u 2 2 and a is the radius of the craft ( a = 8 ft). Density of air = 0.074 lb m /ft 3 . Find the discharge velocity u 2 . Find the weight of the hovercraft. 2. During a torrential rainstorm, water flows down through a section of rain spout and discharges to the atmosphere as shown. The rain spout has cross-sectional area 28cm 2 , and the bulk velocity is 3.6m/s. Let the weight of the water in the spout be W . Find the total force required to hold the spout in place.
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Unformatted text preview: NOTE: Neglect frictional losses, but do not neglect changes in potential energy. 3. Consider a ‘U’ shaped pipe fitting as illustrated. Water at 25 o C enters with velocity of 2.8m/s at pressure p 1 = 15psi (gage). The diameters of the inlet and outlet are 10cm and 8cm, respectively. Assume the flow enters and exits with a uniform velocity and a constant density. • Find the force required to hold the fitting in place. Neglect frictional losses and gravity. 4. A fluid of density ρ 1 enters a chamber where the fluid is heated so that the density decreases to ρ 2 . The fluid then escapes through a vertical chimney that has a height, L 2 . Neglect friction and treat the flow process as incompressible except during heating. Assume the chimney is immersed in a fluid of density ρ 1 . • Determine the velocity, v , in the stack...
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