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Venturi tube help needed in determining pressure difference 
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#1
May2011, 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 (V2^2V1^2)) delta H 1/2 = 39.3mm Where do I go from here, if this is even correct ? Thanks a lot for your help. 


#2
May2011, 05:52 AM

Sci Advisor
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P: 26,160

hi timothy1875! welcome to pf!
(try using the X^{2} and X_{2} 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 


#3
May2011, 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 ? 


#4
May2011, 06:51 AM

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P: 26,160

Venturi tube help needed in determining pressure difference
show us what you have so far



#5
May2011, 07:06 AM

P: 9

V2 = P_{1}A_{1}V_{1}/P_{2}A_{2} = 0.9548 and V1 (Q/A) = 0.3731
delta H 1/2 = H1  H2 = 1/2g (V_{2}^{2}V_{1}^{2}) delta H 1/2 = 39.3mm This where I have got to so far, :( 


#6
May2011, 07:15 AM

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P: 26,160

where does it come from? 


#7
May2011, 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 (V_{2}^{2}  V_{1} ^{2}) ??



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