# Homework Help: Pressure loses

1. Jun 8, 2015

### can12345

1. The problem statement, all variables and given/known data
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?

2. Relevant equations

3. The attempt at a solution

2. Jun 8, 2015

### billy_joule

What frequency are you reffering 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 thier 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.

3. Jun 8, 2015

### can12345

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 seperate 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.

4. Jun 8, 2015

### can12345

The exactly question is actually to check whether pressure loses are negligible in unsteady (turbulent, oscilation) conditions.

5. Jun 9, 2015

### billy_joule

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.

6. Jun 9, 2015

### can12345

How I can determine this velocity? Can you give equation or help please?

7. Jun 9, 2015

### billy_joule

calculate a flow rate from swept volume & frequency.

8. Jun 9, 2015