# HW5_sol - Thermal Fluids Engineering I Spring 2006...

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Thermal & Fluids Engineering I. Spring 2006. Homework #5 Solution. WebCT post date: 02/24/2006 4-2 Hoover dam stands at a height of 725 ft above the Colorado river. Assuming atmospheric pressure is 14.7 lbf/in. 2 , calculate the pressure in the reservoir at the base of the dam. Approach: Use the equation for pressure as a function of depth in an incompressible fluid: P = atm P + . gh ρ Assumptions: 1. The density of the water is constant. 2. The water is at room temperature (70ºF). Solution: At an assumed temperature of 70ºF, the density of water (from Table B-6) is 2 H O = 62.2 3 lbm/ft The pressure in an incompressible fluid as a function of depth is P = atm P + gh = ( ) 2 2 3 2 2 2 lbf lbm ft 1 lbf 1ft 14.7 62.2 32.2 725ft lbm ft in. ft s 144in. 32.2 s  +    = 2 lbf 328 in. Answer

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Thermal & Fluids Engineering I. Spring 2006. Homework #5 Solution. Page 2 4-12 In the device shown below, calculate the gage pressure of the gas in the tank. Approach: Use the expression for variation of pressure with depth in an incompressible fluid. Assumptions: 1. The densities of the oil and water are constant. Solution: Pressure in a static fluid is only a function of horizontal location, therefore A B P P = 1 1 2 2 B atm P P h g h g ρ = + + The gage pressure is given by 1 1 2 2 g B atm P P P h g h g = - = + ( )( ) ( )( ) 2 2 3 3 3 32.2 ft/s 1ft 32.2 1 32.2 lbm ft/s 3in 49 lbm/ft 8.6 2.2 62.2 1lbf 12in. 32.2 12 g P  = + -   0.316psig g P = Answer
Thermal & Fluids Engineering I. Spring 2006. Homework #5 Solution. Page 3 4-17 A hydraulic lift is used to raise a crate, as shown in the figure below. The large tube has a diameter of 3 ft and the small tube has a 1 in. diameter. The fluid is oil with a specific gravity of 0.86. The plate under the crate has negligible mass. Initially the system is at rest with the oil heights of 1.4 ft and 6 in., as shown. a. Find the mass of the crate, in lbm.

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HW5_sol - Thermal Fluids Engineering I Spring 2006...

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