Home > Industry Knowledge > Content

How to choose suitable Vortex Flowmeter

Jul 03, 2018

How to ensure the performance of bore & flow range for meter

It is important for selecting model, the key to use, so client must read this chapter carefully, and if find question, you can contact us.Ensure the diameter of meter

According to the flow range to choose diameter. Different diameter hold different test range. Even if the same diameter, the test range is different if medium is not same. Practical test range must be confirmed by figure.  

Flow range of air and water under reference condition,as chart II,reference condition as follow:

1.Air:Normal Temp & press,t=20℃,P=0.1MPa(absolute pressure),ρ=1.205 kg/m3,υ=15×10-6 m2/s.

2.Liquid:normal temperature water,t=20℃,ρ=998.2kg/m3,υ=1.006×10-6m2/s.

Basic step to ensure diameter of meter and flow range:

(a)name & component of testing medium

(b)Min, Nor and Max capacity under working condition

(c)Min, Nor & Max Press & Temp of medium

(d)Viscosity of medium under working condition

2.Meter test the flow capacity of medium under working condition, so as the technological parameter to know the flow capacity of medium under working condition, as follows:

(a)if know air capacity under standard condition, we can get the capacity which under working condition, as follow;

1png.png  formula(3)

 (b)if know air density under standard condition ρ,as follow;

2.png formula(4)                             

(c)Mass flow rate Qm charge to volume flow Qv

3.png    formula(5)

Among formula(5):

Qv: volume flow of medium under working condition (m3/h)

(Qv=3600f/K  K: coefficient of meter)

Qo volume flow under standard condition(Nm3/h)

Qm: mass flow rate (t/h)

Ρ: density of medium under working condition(kg/m3)

ρo density of medium under normal state(kg/m3),common air medium density under normal state,as chart III

P:gauge pressure  under working state (MPa)

T:Temp under working state(℃)

3.To ensure lower limit capacity. For the upper limit capacity of flow meter may be not counted under ordinary condition,so that just count its lower  limit for choosing caliber. Shall meet two conditions:Minimum Reynolds number shall be not less than limited(Re=2×104);for vortex flow meter flow meter with stress type set, it take vortex intensity from lower  limit capacity shall be more than limited sensor intensity (vortex intensity and lift force, as scaling relation as ρv2) . Relation as follow:

For density to test measurable lower limit flow:

4.png        formula (6)

For kinematic viscosity to test linear lower  limit flow:

5.png       formula(7)

Medium:

Qρ:Meet request of vortex intensity, the minimum volume flow (m3/h)

ρ0: medium density under reference condition

Qυ:Meet request of Min-Reynolds number, the minimum linear volume flow (m3/h)

ρ: The density of tested medium under working condition(kg/m3)

Q0: minimum volume flow of meter under reference condition (m3/h)      

U: kinematic viscosity of medium under

working condition (m2/s):

Uo: kinematic viscosity of medium under reference condition (m2/s)

by means of formula(6)&(7) to come out Qρ& Qν.compare with Qρ& Qν,to ensure measurable range of lower limit flow & linear lower  limit flow :

Qυ≥Qρ:measurable range= Qρ~Qmax, linear flow range= Qυ~Qmax

Qυ<Qρ:measurable range & linear flow range  Qρ~Qmax  

Qmax:upper limit volume flow (m3/h)

4.The standard of upper limit flow ,See(II). gaseous upper limit flow velocity shall be less than 70m/s, liquid shall be less than 7m/s.