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