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Short Answer Questions

  1. Explain the physical meaning of each term in the mechanical energy balance.

  2. luid flows from a larger-diameter pipe to a smaller-diameter pipe. How does the velocity change?

  3. Explain the concept of pressure head.

  4. luid flows downward in a vertical pipe of uniform diameter. How does the velocity change with position?

  5. liquid flows vertically downward through a pipe of uniform diameter at steady state. Explain how the mass flowrate, volumetric flowrate, and velocity change with vertical position.

  6. Explain the meaning of the Reynolds number in terms of forces.

  7. Sketch the approximate shape of a graph of frictional losses versus Reynolds number. Discuss two other situations in which the graph has similar shape.

  8. There are three key parameters that affect frictional loss in pipe flow. State two of them and explain the effect (i.e., whether the parameter increases or decreases, how the frictional loss is affected).

  9. For sections of pipes in series, what is the relationship between the mass flowrate in each section? What is the relationship between the pressure drops in each section?

  10. For sections of pipes in parallel, what is the relationship between the mass flowrate in each section? What is the relationship between the pressure drops in each section?

  11. How is the mechanical energy balance different for compressible flow compared to incompressible flow?

  12. What is the difference between form drag and frictional drag?

  13. Define void fraction.

  14. Explain the difference between void volume, solid volume, and total volume.

  15. Define sphericity.

  16. When is mercury a better manometer fluid than water or oil? When is mercury not recommended? Assume the specific gravity of mercury is 13.2, and the specific gravity of oil is 0.8.

  17. Explain the physical meaning of the intersection of the NPSHR and NPSHA curves.

  18. Explain the physical meaning of the intersection of the pump and system curves.

  19. Why does a compressor cost more to operate than a pump?

  20. Why are compressors often staged with intercooling?

  21. For fully developed turbulent flow, assuming all variables not mentioned are held constant:

    1. What is the effect of doubling the flowrate on the pressure drop?

    2. What is the effect of increasing the pipe diameter by 25% on pressure drop?

    3. What is the effect of increasing the pipe diameter on flowrate?

    4. What is the effect of increasing pipe length on pressure drop?

    5. What is the effect of increasing pipe length on flowrate?

    6. What is the effect on pressure drop of replacing one long pipe segment with two equal-sized pipe segments of half the length placed in parallel?

  22. Repeat Problem 19.21 for laminar flow.

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