permanent pressure losses in venturis

[atticus]

Does anyone know how to calculate the permanent pressure loss associated with a venturi? I have a permanently deformed section of pipe that approximates the shape of a 0.5 beta venturi and want to know what kind of permanent pressure loss this section is creating. I can't reach it to install pressure taps--it's buried.

 

[m777182]

Hello Aticus,
In the EN ISO 5167-1 (1995) and EN ISO 5167-1:1995:A1 (April 1998) you will find a complet calculation of a Venturi( as well as for orifice and for nozzle).In a supplement D there is a graphical solution for pressure loss. It depeds on relative smoothness of the surface, Re number,beta and diffusor angle. My version is in German language.
M777182

 

[tgreif]

Go here

http://www.bifwater.com/venttable.htm#2 to 6

The tables give the flow at 100-inches water column differential pressure and the permanent loss is in the table column "Loss". The permanent loss is generally 7-15% of the differential.

 

[sbei]

Permanent pressure loss for flow meters is expressed as a percentage of meter DP, which you aren't able to measure. You would be better off approximating your bent piece of pipe as a contraction followed by an enlargement. Use the equations found in Cameron Hydraulic data (in my 16th edition, page 3-118) or Crane Technical Paper No. 410, page A-26.