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Venturi tube help needed in determining pressure difference

by timothy1875
Tags: determining, difference, pressure, tube, venturi
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timothy1875
#1
May20-11, 01:16 AM
P: 9
1. The problem statement, all variables and given/known data

Water flows through venturi tube at 0.3 litres/s. Diameter of venturi tube is 32mm to 20mm to 32mm and the water density is 1000kg/m^3.


2. Relevant equations

a) Assuming head loss is neglible, what is pressure difference between 1 and 2.

b) If pressure head difference between these is 45mm what is head loss.


3. The attempt at a solution


So far I have V2 = P1A1V1/P2A2 = 0.9548 and V1 (Q/A) = 0.3731

delta H 1/2 = H1 - H2 = 1/2g (V2^2-V1^2))
delta H 1/2 = 39.3mm

Where do I go from here, if this is even correct ?

Thanks a lot for your help.
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tiny-tim
#2
May20-11, 05:52 AM
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hi timothy1875! welcome to pf!

(try using the X2 and X2 icons just above the Reply box )

i don't follow you

use the fact that the volume per time is constant, and Bernoulli's equation
timothy1875
#3
May20-11, 06:49 AM
P: 9
Hi Tim,

Thanks for getting back to me.I am trying to answer the question but think I may be going about it the wrong way.

Using the Bernoulli equation do I need to transpose to find P ?

tiny-tim
#4
May20-11, 06:51 AM
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Venturi tube help needed in determining pressure difference

show us what you have so far
timothy1875
#5
May20-11, 07:06 AM
P: 9
V2 = P1A1V1/P2A2 = 0.9548 and V1 (Q/A) = 0.3731

delta H 1/2 = H1 - H2 = 1/2g (V22-V12)
delta H 1/2 = 39.3mm

This where I have got to so far, :(
tiny-tim
#6
May20-11, 07:15 AM
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Quote Quote by timothy1875 View Post
V2 = P1A1V1/P2A2 = 0.9548
what does this mean?

where does it come from?
timothy1875
#7
May20-11, 07:25 AM
P: 9
Basically we have been set this question and there are numerous equations on the back that we have to pick from. I take it from your response I have selected the wrong equation initially. Should it be 1/2g (V22 - V1 2) ??


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