Flow Measurements• Identify an effect that depends on flowrate

– Mixing of two streams– Feed rate into a combustion chamber– Heat exchangers– Velocity

• Flowmeters– Size– Accuracy– Media– Cost– Pressure drop– Pressure losses

Bucket Flow Meter

Rotameter

• Force balance– Drag Force– Gravity – Buoyancy

Turbine Flow Meters

Doppler / Ultrasonic Flowmeter

Magnetic Flowmeter

Faraday’s Law

Conductive fluid moving through a magnetic field induces a voltage.

Thermal Mass Flowmeter

• Non-streamlined object placed in the middle of a flow stream

• Vortices are shed alternately downstream of the object.

• Frequency of the vortex shedding is directly proportional to the velocity of the liquid flowing in the pipeline.

• Ultrasonic, electric, or fiber optic transducers

Vortex Shedding

Obstruction Flow Meters

Δp

QSharp-Edged

Orifice

Δp

Long Radius Q

Nozzle

Δp

Q

Venturi

Flow through a Nozzle

1

1

1

1

v

A

m

2

2

2

2

v

A

m

a.) Continuity

mass in = mass out

b.) Bernoulli’s equation

Total pressure is constant throughout

If incompressible fluid (like water):

Bernoulli’s Equation

Bernoulli’s Equation for Total Pressure

Flow through a Nozzle

P2

A

A1

1YCAQ

FlowalReFor

IdealP2

A

A1

1AvAQ

RateFlow

P2

A

A1

1v

2

1

2

2

2

1

2

222

2

1

2

2

Flow through a Nozzle

Y = Compressibility Factor

=1 for incompressible flow or when DP<< Pabs

C= Discharge Coefficient

=f(Re) and

nature of specific flow meter

Airfoil Lift

Pitot Tube

Pitot Tube

Flow Types – Reynolds Number

• Reynolds number is a ratio of inertial to viscous flows

• Re < 2000 – Laminar Flow• Re > 4000 – Turbulent Flow

Nozzle Flowmeter Example

Car Example

• Rick Perry is holding a Chick-Fil-A Cup out a car window. • Texas is basically at sea level (102,325 Pa); (1.225 kg/m3)• Somehow, Rick also has a pressure gauge facing in the direction of

travel reading 680 Pag.• How fast is the car going (mph)?