Fluid Mechanics: Differential Hg Manometer

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SUMMARY

The discussion centers on calculating the differential reading, h, of a differential mercury manometer connected to two pipes: one containing gasoline (specific gravity 0.65) and the other containing water. Given a pressure of 20 kPa in pipe A and a vacuum of 150 mm Hg in pipe B, the absolute pressure in pipe B is determined to be 610 mm Hg. This implies that the pressure in pipe A is effectively 1 atm plus the additional 20 kPa, which is crucial for solving the manometer problem.

PREREQUISITES
  • Understanding of fluid mechanics principles
  • Knowledge of specific gravity and its implications
  • Familiarity with manometer equations and calculations
  • Basic grasp of pressure measurement units (kPa and mm Hg)
NEXT STEPS
  • Study the principles of hydrostatic pressure in fluids
  • Learn how to calculate pressure differences using manometer equations
  • Explore the concept of specific gravity and its applications in fluid mechanics
  • Investigate the relationship between absolute pressure and gauge pressure
USEFUL FOR

This discussion is beneficial for students studying fluid mechanics, engineers working with pressure measurement systems, and anyone involved in solving practical problems related to manometers and fluid dynamics.

nicmat42
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Homework Statement


A differential mercury manometer is connected to pipe A containing gasoline (SG=0.65), and to pipe B containing water. Determine the differential reading, h, corresponding to a pressure in A of 20kPa and a vacuum of 150 mm Hg in B.


Homework Equations


Distance from pipe A to fill line is 0.3 m and distance from pipe B to other fill line is 03 m.


The Attempt at a Solution


I have done a few manometer problems before, however, I am not sure what to make of the "vacuum of 150 mm Hg in B". I do not know what this is implying to the problem?
If someone could kindly explain I would be very grateful and will be able to complete the question.
Thanks
 
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It sounds like they are talking about the pressure relative to 1 atm (760 mm Hg).

So the "vacuum of 150 mm Hg" means an absolute pressure of (760-150) or 610 mm Hg.

This probably means the 20 kPa pressure is really 1 atm + 20 kPa.
 

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