Thermal Mass Flowmeter Sensyflow FMTFundamentals & Measuring Principle

ABB ATPA Measurement Products VIK Gert van Bergen

Sensyflow FMT – Fundamentals Overview

Overview

Physical basics

Measuring principle

Design and characteristics of the sensor

Calibration

Summary

Sensyflow FMT – Fundamentals Overview of flow rate and flow metering principles

Flow Rate and Total Metering Instruments

Closed Pipe Lines Open Channels and Free Surface Pipe Lines

Flowmeters

Rectangular and V-Notch

WeirsVenturi

Flume MeterElectro magnetic

Flowmeter

Total Flow MetersTotalizers Flowmeters

Direct (Displacement

Totalizers)

Indirect(Displacement

Totalizers)Volumetric Mass

Oval GearMeter

OscillatingPiston Meter

Lobed Impeller Meter

Turbine,Rotary Vane, Woltmann, Spiral Gear

Meter

VortexFlowmeter

Swirl Flowmeter

DifferentialPressure Flowmeter

Variable AreaFlowmeter

Electro magneticFlowmeter

UltrasonicFlowmeter

MassFlowmeter

Coriolis

MassFlowmeterThermal

availableat

Sensyflow FMT

Example: Air

V = 2.3 m3

T = 40 °Cp = 5.0 bar

n = 1.429 kg/m³

m = 14.29 kg

Vn = 10 m3

Tn = 0 °Cpn = 1.013 bar

n = 1.429 kg/m3

m = 14.29 kg

Normal condition Operating conditions

Sensyflow FMT – Fundamentals Volume Flow – Mass Flow

= mV

The gas mass is constant and does not depend on pressure and temperature.

Abstraction of heat from a heated body by an enveloping gas flow (Hot-film Anemometer)

T between Rh and RT = constant

The loss of heat depends on the number of molecules that collide with Rh

.m: Mass flow

Ih: Heating current

Rh: Platinum thin-film resistor – electrically heated

RT: Platinum thin-film resistor – gas temperature

Sensyflow FMT – Fundamentals The thermal measuring principle

RhRT

Ih.m

Sensyflow FMT – Fundamentals The thermal measuring principle

.m

Ih

RhRT

Abstraction of heat from a heated body by an enveloping gas flow (Hot-film Anemometer)

T between Rh and RT = constant

The loss of heat depends on the number of molecules that collide with Rhm: Mass flow

Ih: Heating current

Rh: Platinum thin-film resistor – electrically heated

RT: Platinum thin-film resistor – gas temperature

heatingelement

sensor for gastemperature

Temperature sensorfor heater

CPU

.mTAlarms,Diagnostics

separate temperature sensor for the heater element

direct measurement of the gas temperature

Digital signal processing

fast response time < 0.5 s

But: outer sensor shapeidentical to VT-series

Thermal FlowSensyflow FMT – Fundamentals The DIGITAL measuring principle

100 200 300 400 500

.m / [kg/h]

Ih / [mA]

300

400

500

410

Sensyflow FMT – Fundamentals Characteristic curve

.The heating current Ih is a measure for the mass flow rate m

For ambient air in a 40 mm pipe

approx.

280 km/h

20 km/h

Sensor element

Capillary

WiresHull

Sensyflow FMT – Fundamentals Sensor construction and mechanical protection

Heat

Sectional view

Gas flow

Top view

Protection bar

The protection barsdefend the sensor fromdamage by dirt andother objects!

Sensor element

Capillary

WiresShealth

Sensyflow FMT – Fundamentals Sensor construction and mechanical protection

Thin sensor element Small surface for dirtSmall sensor mass Quick responseSmall flow restriction Low pressure loss

Heat

Sectional view

Gas flow

Top view

Protection bar

Sensyflow in a pipe DN40:

Measuring range: 0(3) … 450 kg/h Pressure drop: max. 3 mbar

0

20

40

60

80

100

120

140

Sensyflow FMT Vortex Orifice0

50

100

150

200

250

300

Sensyflow FMT Vortex Orifice

Turn down ratio 1:x

Pressure drop mbar

Sensyflow FMT – Fundamentals Comparison: Measuring range and pressure drop

High turn down ratio start-up and full load measurement with one instrument

Low pressure drop no additional energy costs

Sensyflow FMT – Fundamentals Measuring Accuracy

0,00%

10,00%

20,00%

0 500 1000 1500 2000 2500

FMT500-IGOrificeCompetitor

Member of ‚Deutscher KalibrierDienst‘ DKD with two calibration facilities

Calibration range: 1 … 8800 kg/h air

High accuracy: <0.3 % of reading

proven and certified by the German PTB (physical and technical federal agency)

Calibration certificate included in delivery

Sensyflow FMT – Fundamentals Flow Calibration DKD

Unique calibration bench for gas flow measurement

Certified for flammable and non-toxic gases ( e.g. methane, hydrogen, carbon dioxide…)

High accuracy by PTB-approved references

Pressures up to 40 bar

Sensyflow FMT – Fundamentals Calibation bench for process gases

Sensyflow FMT – Fundamentals Summary

Full load measurement and leakage

detection with one isntrument

No additionalenergy costs

No additionalpressure and temperature

compensation necessary

Quick process control

Wide measuring

range

Short response

time

Low Pressure

drop

Directmeasurement of mass flow