Sierra 240-VTP, 241-VTP instruction manual Flow Velocity Range, Gas Liquid

Series 24-HP Instruction Manual Chapter 1 Introduction

Flow Velocity Range

To ensure trouble-free operation, vortex flow meters must be correctly sized so that the flow velocity range through the meter lies within the measurable velocity range (with acceptable pressure drop) and the linear range.

The measurable range is defined by the minimum and maximum velocity using the following table.

	Gas	Liquid
	25 ft/s		3
Vmin	ρ	1 ft/s
			English ρ (lb/ft )
Vmax	300 ft/s	30 ft/s
	37 m/s		3
Vmin	ρ	0.3 m/s
			Metric ρ (kg/m )
Vmax	91 m/s	9.1 m/s

The pressure drop for series 241 insertion meters is negligible. The pressure drop for series 240 in-line meters is defined as:

ΔP = .00024 ρ V2	English units (ΔP in psi, ρ in lb/ft3, V in ft/sec)
ΔP = .000011 ρ V2	Metric units (ΔP in bar, ρ in kg/m3, V in m/sec)

The linear range is defined by the Reynolds number. The Reynolds number is the ratio of the inertial forces to the viscous forces in a flowing fluid and is defined as:

ρ V D

Re =

Where ∝

Re = Reynolds Number

ρ= mass density of the fluid being measured

V	=	velocity of the fluid being measured
D	=	internal diameter of the flow channel

∝= viscosity of the fluid being measured

The Strouhal number is the other dimensionless number that quantifies the vortex phenomenon. The Strouhal number is defined as:

f d

St =

Where V

St = Strouhal Number

f= frequency of vortex shedding

d = shedder bar width

V = fluid velocity

IM-24-HP 1-5