##### From Chemical Engineering License Review, Second Edition

## Permanent Pressure Loss

**Venturi** Permanent pressure loss through venturis depends upon the diameter ratio ? and the discharge cone angle ?. The pressure loss for smaller angles (5 to 7 ) is 10 to 15 percent of the total pressure differential ( *P* _{1} ? *P* _{2}). It is 10 to 30 percent for large angles (> 15 ).

**Subsonic Flow Nozzles** For subsonic flow nozzles, the pressure loss is given by

where ? is the nozzle throat diameter divided by the pipe diameter.

**Concentric Circular Nozzles** In the case of the concentric circular nozzle,

A venturimeter is to be installed in a schedule 40, 6-in line to measure the flow of water. The maximum rate is expected to be 800 gpm at 86 F. A 50-inHg manometer is to be used. Specify the throat diameter of the venturi and calculate the power required to operate it. The discharge cone angle is 5 .

** Solution.** From Eq. (2-14),

*C* = 0.98 for venturis if *N* _{Re} > 10,000 (i.e., fully turbulent flow). Assume fully turbulent flow. Then

where *D* _{ P} is the inside diameter of pipe, ft. Squaring both sides, one obtains

Simplifying and solving for *D* _{ T} gives

Use 2.375 in = 0.1979 ft (a standard size). Check the Reynolds number through the throat of the venturi.

This *N* _{Re} is greater than 10,000 and therefore the flow is in the fully turbulent region. Therefore, the size of...

##### Products & Services

##### Topics of Interest

Flow of Fluids in Pipes The nature of the flow of a fluid in a pipe depends upon the Reynolds number which is defined as where D = inside diameter of pipe, ft u = velocity of fluid, ft/s ? =...

Critical or sonic flow has a long historical background. However, substantial use of critical flowmeters did not begin until the 1960s. Critical flowmetering had acceptance first in the aerospace...

10.5 Starting and Operation of Supersonic Diffusers and Inlets 10.5.1 The problem of starting a supersonic flow The relations developed for one-dimensional flow describe steady-state operation at...

FRICTIONAL PRESSURE LOSSES Frictional pressure losses inside the drill string are usually measured while frictional pressure losses in the annulus in conventional operations are usually ignored.

40.3 Line Sizing for Low-Viscosity and Turbulent Flow Just as we used this simple formula: () earlier in this chapter to evaluate pipeline pressure drop, we can also use this same formula to check...