Homework #12ME 363 - Fluid Mechanics
DueFriday, April 25, 2008Fall Semester 2008
1]Water at 15 degrees C (ρ=1000 kg/m3, μ=1.3e-3 kg/m*s) is flowing steadily in a 30-m long, 4-cm-diameter horizontal pipe. The pipe is made of stainless steel with a roughness e = 2 μm. The flow rate is 8 L/s. Find the pressure drop.
2]Oil at 80 degrees F (ρ = 56.8 lbm/ft3, μ=0.0278 lbm/ft*s) is flowing steadily in a 0.5” diameter, 120’-long horizontal pipe. The pressure at the pipe inlet is measured to be 120 psi and the pressure at the outlet is measured to be 14 psi. Determine the flow rate of oil through the pipe in ft3/s.
3]Glycerin at 40 degrees C with ρ = 1252 kg/m3 and μ = 0.27 kg/m*s is flowing through a horizontal, 10-m-long, smooth pipe with an average velocity of 3.5 m/s. Plot the pressure drop versus pipe diameter for pipe diameters between 1 and 10 cm. What conclusions do you draw from the plot?
4]Shell-and-tube heat exchangers with hundreds of tubes housed in a shell are commonly used to transfer energy between two fluids. Such a heat exchanger used in an active solar hot-water system transfers heat from a water-antifreeze solution flowing through the shell to fresh water flowing through the tubes at an average temperature of 60 degrees C and at a rate of 15 L/s. The heat exchanger contains 80 brass tubes 1 cm in diameter and 1.5 m in length (roughness e = 1.5 μm). Disregarding inlet, exit, and header losses, determine the pressure drop across a single tube and the pumping power (using eq 8.47) required by the tube side of the heat exchanger. After operating for a long time, a 1-mm thick scale with a roughness e of 0.4 mm builds up on the inner surfaces. For the same pumping power input, determine the percent reduction in flow rate of water through the tubes.
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Problem #4