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  1. stewartcs

    Solar updraft tower: How small a working unit can be made?

    Pretty sure there are commercial ones already out there. I seem to recall some discussions here years ago about one in either the middle east or Australia? I don't think the economics are they now which why they're not more around. Fossil fuels are too cheap (especially recently). CS
  2. stewartcs

    Brainstorming for a self-directed class project

    I imagine it would depend on which class you're taking. Assuming it's a fluid mechanics or thermo class I would suggest one of the following: - drag reduction devices on cylindrical vessels (i.e., long vertical pipes in the ocean subjected to ocean currents) - gas bubble dynamics in...
  3. stewartcs

    Friction loss to vertical pipes in a closed system?

    Technically you should consider the elevation changes so you can size your pump correctly. I imagine that since it's a closed loop system that is being constantly recirculated that you'll end up with the same answer. Why not just run a couple of hand calcs and do one like you've been doing it...
  4. stewartcs

    Pipe wall thickness, barlow equation problem

    Can you describe the application a little bit? Are you using any particular codes (API, ASME, etc.)? Pipe burst pressures are determined using widely different safety factors depending on the code you're using and the application. Regardless, I don't recommend copying an example to perform...
  5. stewartcs

    Function of an accumulator with a pump

    Heat transfer in accumulators is a tricky thing actually. If you charge or discharge the accumulator slowly (assuming you're using reasonably low system pressure), then you can use the Ideal Gas Law and some other process like Isothermal to get a reasonable answer on the relationship between the...
  6. stewartcs

    Pressure Drop due to Vortex Shedding

    MIT has a bunch of data of VIV. Take a look here, it should give you a good starting point for your research: Hope this helps. CS
  7. stewartcs

    Strain Hardening vs Colding Rolling

    No. The elastic modulus is relatively insensitive to cold working. CS
  8. stewartcs

    Principal Virtual Work Theories - Cylindrical Pipe Application

    Principle of Virtual Work: I've never used this principle for determining collapse or bucking of pipe. API Bulletin 5C3 gives lots of guidance on how to determine pipe collapse resistance. Buckling is normally...
  9. stewartcs

    Pump flow rate question

    That's the max flow rate the pump can output at those specific pressures. So if your system has a higher back pressure than the pump can output, the flow rate will decrease. If the system back pressure is less than the rated pump pressure, the flow rate can increase. I would ask the...
  10. stewartcs

    Engineering Becoming an engineer at age 50

    You don't necessarily have to be employed by a company, you can always consult as well. If it's been your lifelong desire then nothing bad will come of it. CS
  11. stewartcs

    Calculating Fluid Dynamic Forces on a Towing Cable

    Can you provide a diagram of what you're trying to figure out? I'm not clear on what you want to know. It seems you are asking how to calculate the depth of the "rig" on the end of a cable/line that is being dragged through the water; is that correct? CS
  12. stewartcs

    Electric Generators

    Electric Machines by Hubert: CS
  13. stewartcs

    Flow rate to height

    Use Bernoulli's Equation. You can make a few assumptions and end up with this equation: v = \sqrt{2g\Delta{h}} Multiply that time the area of the hole in the bottom and you end up with the flow rate (which you are given). Q = A\sqrt{2g\Delta{h}} Solve for h (the height) and plot...
  14. stewartcs

    Hydraulic or pneumatic for applying loads ranging between 500-1000lb

    You could technically use either, however, the hydraulic system will have a better response than the air one. Imagine pressuring up with a compressible medium - you'll have a sudden expansion in the cylinder as soon as it moves which will cause the pressure to drop rapidly. With a hydraulic...
  15. stewartcs

    Mass flow in Vapor Compression Cylce HELP

    Based on the Conservation of Mass principle, the mass flow rate is constant for a tube with one inlet and one outlet (i.e. no mass is gained or lost). The volumetric flow rate, however, may certainly change. CS
  16. stewartcs

    Stability of a body floating in a liquid-relation betncentre of buoyancy and gravity

    Center of Buoyancy (B) below the Center of Gravity (G) doesn't necessarily mean a floating body is stable. As your intuition tells you, it depends on the righting arm (i.e. restoring moment). In the examples you show, the floating body is not stable. If your floating body has the G directly...
  17. stewartcs

    Pressure drop in elbows & bends in a pipe

    What kind of model? The equations have already been given in the earlier threads. CS
  18. stewartcs

    Soil Mechanics: Relationship between pH of seawater and sand

    Some research has shown that the pH of the solution can effect the tensile strength for some sand soil combinations. Apparently a lower pH solution increases soil particle bonding stress and thus increases tensile strength. Check out...
  19. stewartcs

    Electrical, Electronics or Mechanical engineer?

    DOE...but usually around $70,000 USD is the national average IIRC. CS
  20. stewartcs

    Real gas equations for air

    There are quite a few equations of state that can be used to describe fluids in the gas phase. A very simple, although not to accurate one is Van der Waals. A more accurate one is Redlich-Kwong. The latter gives good results.–Kwong_equation_of_state CS
  21. stewartcs

    Electrical, Electronics or Mechanical engineer?

    Go with either a BS in Electrical Engineering or Mechanical Engineering. You'll have more options in your career and you'll learn more. Electronics Engineering is probably a technology type degree which isn't as comprehensive. CS
  22. stewartcs

    Fatigue analysis:frequency domain vs time domain

    I don't know of any classification societies that require a specific method...although they may recommend one or the other. Risers are actually one of the more complicated structures to model in engineering. I'm not sure why you think they don't compare to others...perhaps you could provide...
  23. stewartcs

    How does a pressure reducing valve work?

    Just for clarity, a pressure regulator, which is a type of pressure reducer, does not require any flow to reduce the pressure. CS
  24. stewartcs

    Pressure relief valve safety considerations during design

    You should design the PRV to an industry standard. You can also verify the that the orifice is the correct size with the same standard. CS
  25. stewartcs

    Fatigue analysis:frequency domain vs time domain

    Why do you think time domain analyses cannot be performed often? Most always one should analyze a dynamic system in the time domain to get the most accurate results...especially with risers. The reason being is that the lateral effects are not accurately assessed with a frequency domain method...
  26. stewartcs

    Are business degree profitable?

    So you are privy to business student's grades then? I see no correlation between being lazy and studying business - it's just a different field that appeals to different personalities. CS
  27. stewartcs

    Are business degree profitable?

    That's a load a crap. There are certainly many intelligent people who studied Business Administration. CS
  28. stewartcs

    Fluid dynamics problem

    Can you provide a sketch? CS
  29. stewartcs

    Von mises smaller than tresca

    Perhaps you've made the same error 1000 times. If you don't show your work, we can't help you. CS
  30. stewartcs

    Some basic questions

    1. Most any high level programming language will be beneficial. However, I personally preferred C++ and VB. 2. As many as you can! Each company will most likely use a different software. ANSYS products are good in general. 3. Doesn't matter IMO. CS