Pressure Loss in Transmission Line: Analyzing Reducing Union, Filter & L Pipe

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Discussion Overview

The discussion revolves around analyzing pressure loss in a transmission line that includes a reducing union, filter, and L pipe, particularly focusing on the effects of these components on pressure measurements and fluid dynamics. Participants explore the implications of turbulent flow and oscillations on pressure loss, as well as the relationship between pipe diameter and frequency.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant seeks to define pressure losses through a transmission line to a transducer, specifically considering a reducing union that changes the pipe diameter from 6 mm to 3 mm.
  • Another participant suggests using the Darcy-Weisbach equation for major losses and refers to minor loss coefficients for fittings, indicating that pressure loss may be zero if there is no flow.
  • A participant describes the behavior of a diaphragm under turbulent flow, noting that the deflection rate is small during fluid impact but may lead to backflow, raising questions about the significance of these effects.
  • There is a focus on determining whether pressure losses are negligible under unsteady conditions, particularly during oscillations.
  • One participant questions the reliance on estimates for velocities and suggests calculating them directly from transducer data.
  • A request for equations to determine velocity is made, indicating a need for further assistance in calculations.
  • Another participant proposes calculating flow rate based on swept volume and frequency, hinting at a method to relate these parameters.
  • A link to literature discussing pressure loss characteristics in unsteady conditions is shared, emphasizing the dependence on various factors such as the type of pressure probe used.

Areas of Agreement / Disagreement

Participants express varying viewpoints on the significance of pressure losses and the methods to analyze them. There is no consensus on whether the pressure losses are negligible or how to best approach the calculations involved.

Contextual Notes

Participants mention various assumptions regarding flow conditions, the impact of diaphragm oscillations, and the need for specific equations, but these aspects remain unresolved and depend on further clarification and exploration.

can12345
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Homework Statement


I would like to define pressure loses through transmission line to the transducer. In transmission line I have a reducing union, filter and L pipe. How I can find this differences?

In case of frequency my reducing union reduce pipe diameter 6 mm to 3 mm how i can determine my frequency by these two diameter value?

Homework Equations

The Attempt at a Solution

 
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Can you give more information?
What frequency are you referring to?

Pressure loss in pipe work due to friction ('major losses') is generally found via:
http://en.wikipedia.org/wiki/Darcy–Weisbach_equation

Pressure loss due to fittings are 'minor losses', the coefficicnt for your fittings may be found in their datasheets or from general tables:
http://www.engineeringtoolbox.com/minor-pressure-loss-ducts-pipes-d_624.html
http://www.engineeringtoolbox.com/minor-loss-coefficients-pipes-d_626.html

If this is just a dead end line to a pressure gauge then there is no flow and the pressure loss is zero.
 
I actually try to define the pressure loss through diaphragm. When turbulent flow is acting to pressure diaphragm, there is two situation. First of all the diaphragm is always under oscillation. This is the reason why I want to separate the problem into 2 section. First of all when fluid is coming and crushing with diaphragm and extending it, the deflection rate is so small but when it goes back it makes back flow. and velocities are really small I guess, but my advisor wants me to know it. If its negligible still he wants me to find why it is negligible. Boundary conditions are min deflection and maximum deflection.
 
The exactly question is actually to check whether pressure loses are negligible in unsteady (turbulent, oscilation) conditions.
 
can12345 said:
First of all when fluid is coming and crushing with diaphragm and extending it, the deflection rate is so small but when it goes back it makes back flow. and velocities are really small I guess, but my advisor wants me to know it.
Why not calculate the velocities rather than guessing? A raw feed from the transducer should show the oscillation frequency.
What literature have you found on the topic? This is an old problem, it's why gauges are liquid filled, probably since their invention. I'm sure research has been done in the area.
 
How I can determine this velocity? Can you give equation or help please?
 
calculate a flow rate from swept volume & frequency.

billy_joule said:
What literature have you found on the topic?
 

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