Posted: 11/28/2004 2:41:07 PM EDT
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Problem 1) Air at standard temperature and pressure flows through a 1-in. diameter galvanized iron pipe with an average velocity of 10 ft/s. What length of pipe produces a head loss equivalent to (a) a flanged 90 degree elbow K=0.3, (b) a wide open angle valve K=2, (c) a sharp-edged entrance K=0.5? K is the loss coefficent. Roughness for the iron pipe is 0.0005 feet. Problem 2) At a ski resort, water at 40 degrees F is pumped through a 3 in. diameter, 2000 ft. long steel pipe from a pond at an elevation of 4286 ft to a snow making machine at an elevation of 4623 ft at a rate of 0.26 cubic feet per second. If it is necessary to maintain a pressure of 180 psi at the snow making machine, detemine the horsepower added to the water by the pump. Neglect minor losses. Roughness for the steel pipe is 0.00015 feet. Problem 3) Water flows past a flat plate with an upstream velocity of U = 0.2 m/s. Determine the water velocity a distance of 10mm from the plate at distances of x = 1.5 m and x = 15 m from the leading edge. thanks Scott |
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Standard answer: If you are having problems with this stuff, SEE YOUR PROFESSOR OR ONE OF HIS GRAD STUDENT ASSISTANTS! Once you understand the scope of the problem and break it down, it is plug and chug. Come on! Fluids was one of the easiest of my math intensive classes. If you are trying to impress us unwashed masses with what you are studying that is a whole 'nother problem we can't help you with. |
My professor is chinese and I am not trying to impress anbody. And I agree that fluids is one of the easiest classes as I have gotten a 96 and 100 on both tests this semester. It's just some questions I have a hard time starting. If you dont beleieve me, I will post a scan of the tests. |
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Just do what us professionals do. Get yourself a Crane manual www.cranevalve.com/store.htm, and start crankin'. No one promised it would be fun. |
| Crane is the way that real engineers solve problems like that once they get out of school. That stuff is right out of your textbook and is easy if you have the equations and loss tables in front of you. Don't make me have to look for my 30 year old Fluid Mechanics textbook. |
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Take a look at the examples worked out here: Link The examples are fairly close to the problems your prof gave you and you should be able to figure out your problems using the approach in the example. |
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Good Problem!! If my mind wasn't already on the fritz, I would recommend to myself a review of of the Fanning Equation. I haven't followed this thead to it's entirety, but would like to work on it. Nice to see some old Chem. Engr's around this site! Talk with you later. |
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Oops...sorry. Jim, that won't work in this example as this is Scottryan's post involves the pipe roughness. The effect of pipe-surface characteristics must then be taken into consideration, otherwise your approach will arrive at a poor correlation. The solution is arrived through consideration of the total mechanical-energy balance. As Problem 1) deals with a compressible fluid (air) at STP, then either the Fanning Equation: F = 2f((V^^2*L)/(gD)) solved for L (length) where: F=Friction V=Velocity g=ft-lb force/lb mass D=Diameter of pipe Because a pipe fitting is involved, mechanical energy is lost., so a fictitious Length must be used in the above equation. This length is equivalent to the length of pipe, having the same nominal diameter at the fitting. The actual length of the pipe plus the fictional length can be substituted for L in the above equation. This fictitious length for the standard pipe fittings in Problem 1) as: 2.67 ft for a 90 degree elbow. Okay...done in again. When I have time, I'll find the data to answer b) and c) of Problem 1) |