General Overview

2. General Overview Flow Measurement

3. “I do not see to many badly manufactured flow meters. I know a few badly calibrated flow meters, but I have seen loads and loads of badly applied flow meters in the world”

4. Market Ultrasonic: 420 Mln Thermal Ind: 138 Mln Corioles: 460 Mln Vortex: 320 Mln All in U$ Now guess how big the Scientific Thermal market is Yesse Yoder: Total worldwide flow market is 5.5 Bln U$ in 2014

5. World market Thermal Mass flow controllers

6. Flow Measurement Technologies

7. Metering of Gas Flow is difficult because… Gas is compressible. The volume of a given quantity of molecules of gas is strongly depended of the pressure and temperature. 99% of the applications are not related to volume, but to the number of molecules. Examples: Chemical: the molecules do the work!Flame: the molecules do the work!Pneumatics: the molecules to the work!Respiration: the molecules do the work! We want to measure the number of molecules, not the distance between the molecules. We want to measure Mass!

8. Meteringof Gas Flow Flow, as we use it, can be expressed in:- Volume (f.i. l/min)- Standardized or Normalized flow (f.inlpm or slpm)- Real Mass flow (f.i. Gr/min or Kg/hr) Volume and Real Mass are easy, but what about Standardized or Normalized?Standardized or Normalized means “Referred to predefined conditions”. In case of gas it means predefined Pressure and Temperature, because those are variables that relate Mass to Volume.The relation between Volume, Pressure and Temperature for gasses is defined in the Law of Boyle/Gay-Lussac

9. Meteringof Gas Flow The Law of Boyle-Gay/Lussac Where: P = Absolute Pressure (Units should be same on both side of the equation) V = Volume (Units should be same on both side of the equation) T = Temperature (Units should always be in degrees K (=273.15 + °C) Example: I have a balloon at surface conditions filled with air. The volume of the balloon is 2 liter. I take the balloon under water to a depth of 10 meter where it is 10°C. What will be the new volume? Surface conditions: 30°C and 1000 mBara Pressure at 10 meter under water: 1 Barg

10. Meteringof Gas Flow The Law of Boyle-Gay/Lussac Example: I have a balloon at surface conditions filled with air. The volume of the balloon is 2 liter. I take the balloon under water to a depth of 10 meter where it is 10°C. What will be the new volume? Surface conditions: 30°C and 1000 mBara Pressure at 10 meter under water: 1 Barg V2= 0.934 liter

11. Meteringof Gas Flow The Law of Boyle-Gay/Lussac Withthislawoperatingconditionscanbeconvertedinto normal orstandardconditions Vn, Tn, Pnvolumetricflow rate, temperatureandpressureunderreferenceconditions Vx, Tx, Pxvolumetricflow rate, temperatureandpressureunderoperatingconditions

12. Meteringof Gas Flow So what are the pre-defined reference conditions for Standardized or Normalized volume or flow?Standardized: 70°F (21.1°C or 20°C) and 1013.25 mBaraNormalized: 0°C and 1013.25 mBaraHowever not everybody uses this!! Natural Gas Industry: 15°C and 1013.25 mBaraOther manufactures: 20°C and 1013.25 mBaraStandardized and Normalized are often reversed!

13. Normal or Standard Conditions See: http://en.wikipedia.org/wiki/Standard_cubic_feet_per_minute Standard cubic feet per minute (SCFM) is the volumetric flow rate of a gas corrected to "standardized" conditions of temperature and pressure. However, great care must be taken, as the "standard" conditions vary between definitions and should therefore always be checked. Worldwide, the "standard" condition for pressure is variously defined as an absolute pressure of 101,325 pascals, 1.0 bar (i.e., 100,000 pascals), 14.73 psia, or 14.696 psia and the "standard" temperature is variously defined as 68°F, 60°F, 0°C, 15°C, 20°C, or 25°C. There is, in fact, no universally accepted set of standard conditions. (See Standard conditions for temperature and pressure). The temperature variation is the most important. In Europe, the standard temperature is most commonly defined as 0°C, but not always. In the United States, the standard temperature is most commonly defined as 60°F or 70°F, but again, not always. A variation in standard temperature can result in a significant volumetric variation for the same mass flow rate. For example, a mass flow rate of 1,000 kg/h of air at 1 atmosphere of absolute pressure is 455 SCFM when defined at 0°C (32°F) but 481 SCFM when defined at 60°F (16°C). In countries using the SI metric system of unit, the term "normal cubic metre" (Nm3) is very often used to denote gas volumes at some normalized or standard condition. Again, as noted above, there is no universally accepted set of normalized or standard conditions.

14. TypicalApplications (gases)

15. Variable areaprinciple Verticalmeasuringglasswithconicalinternalshape, in which a definedbodyismadetofloatbytheflowactingfrombelow. Fs = flowresistanceofmeasuringsubstance FG = weightof variable area FA = buoyancyof variable area DS = diameterof variable area DK = innerdiameterofcone

16. Mass or volume? Air Back pressure controller

17. Pressure effect on VA meters

18. Variable areaprinciple Advantages: • Suitableforliquids and gases • Cost-effectivesolution • No electricitysupplyrequired • Visuallycomprehensible • Limit contactoption • Lowpressureloss • Simple design Disadvantages: • Verypressure- andtemperature-dependent • No Mass or Volume really • Limiteddynamics • Verticalmountingposition • Onlysuitablefor transparent media • Limitedaccuracy • Pressureshocks

19. Pressure differential principle Orifice plates V-cone Annubar Pitot tube Wing Etc.

20. Pressure differential principle Advantages: • Suitableforliquids and gases • Simple, robust construction • Numerousmaterials • Anyfrom NW10… • Tried and testedprinciple • High temperatures • No movingparts • Anymountingposition Disadvantages: • Susceptibletowear • Soilingleadstoerrors • Gas measurementswith additional measurementofPabsandTmedium • Inletsections • Limited dynamics (1:3 to 1:6) • Gas type-dependent • Lots of potential leakpoints • Need moreequipment

21. Displacementmeter Directlymeasuresthe total volumeflow. The mechanicalmovementistransferreddirectlyto a countingmechanismor pulse generator. This categoryincludesrotarypistons, gearwheels, vanes, ring pistons, bellows.

22. Displacementmeter Advantages: • Suitableforliquids and gases • Simple, robust construction • High dynamics • Independent of interferences in theflowprofile • Independent of gas type • High precision Disadvantages: • Susceptible to wear • Risk of soiling • Gas measurementswith additional measurement of Pabs and Tmedium • Pulsations • Pressureshockslead to overload • Limitedoperatingpressure and temperature • Leaksthroughmechanicaltolerances

23. Turbine flowmetering A rotorwithturbine blades, supported on a rotatingcenteraxis, supplies a signalthatis proportional to theflow rate due to itsrotarymovements. A minimumflowisrequiredfordrivingtherotor. Designed as a completefittingorplug-in probe.

24. Turbine flowmetering Advantages: • Suitableforliquids and gases • Compact design • Independent of gas type • High precision Disadvantages: • Susceptible to wear • Risk of soiling • Gas measurementswith additional measurement of Pabs and Tmedium • Pressureshockslead to overload • Measurementcannottakeplacefromzero

25. Vortexmeter Vorticesaregenerateddownstreamof a definedbaffle (Kármán‘svortexstreet). The numberofvortices (frequency) is proportional totheflowvelocity.

26. Vortexmeter Advantages: • Suitableforliquids, gases and steam • High dynamics (typically 1:25) • high + Low tempsuited • Calibratewithwateronly • Largely independent of changes in pressure, temperature and viscosity • Digital fromsensorupwards. High long-term stabilitypossiblewith non abrassiveliquids. Disadvantages: • Pulsatingorswirlflowinfluencetheabilitytomeasurelowflows • No measurementpossiblewithlowflowrates (Re < 5000). (Not suitablereallyforlowpressuregasses) • Non-linear below Re of 20.000

27. Coriolis principle Measuringprinciplethatmeasuresthe mass independentoftemperature, pressureand medium. A measuringtubeisbroughtinto resonant vibrationstate. Sensors arefittedattheentryandexitofthemeasuringtube. Withoutflowthesensorsissuesignalssimultaneously. Ifthereisflow a phaseshiftoccursbetweenentryandexit. Thisphaseshiftisdirectly proportional tothe mass flow.

28. Coriolisprinciple Advantages: • Suitableforliquidsand high pressuregases • Direct mass measurement • No “moving” parts • High precision • Independent of flowprofile Disadvantages: • Requireminimum medium density • Relatively high purchaseprice • To someextent sensitive to vibrations

29. Thermal mass measurement Several versions, the main ones are: Immersable sensors (Mainly Industrial) Capillary flow meters CMOS or MEMS Thermal flowmeters

30. Thermal mass measurement Immersablesensors Q, heat carried away by gas stream Mass Flow Sensor Temperature Sensor Tv Ta

31. Thermal mass measurement Immersablesensors

32. Thermal mass measurement Immersablesensors Features Direct Gas Mass Flow Reading Fast Response (1 Sec) No Moving Parts Rugged, 316SS Sensors High Turndown & Rangeability Negligible Pressure Loss Convenient Installation Accuracy 1.5% Flexible due to modern electronics Suitable up to 400 C Specific Considerations Gas dependent, cal with real gas Dry gas only Relative clean gas only Temperature bandwidth 80 C Insertion: installation sensitive Up to 10 Barg

33. Thermal mass measurementCapillaryprinciple • Small capillary tube (0.2 till 0.9 mm) • Platinum windings (PT) • Due to high current, heating of coils • Mass flow cools R1 more than R2 (Max flow 1 till 10 sccm) • PT elements will have difference resistances • Difference in resistance proportional to mass flow through tube

34. Thermal mass measurementCapillaryprinciple • Sensor is placed over a LFE • LFE= Laminair Flow Element • Flow is separated in known ratio • m1 proportional to m2 • Total m = m1 + m2 • Behaviour in principle close to linear

35. Thermal mass measurementCapillaryprinciple Examples of capillary sensors

36. Thermal mass measurementCapillaryprinciple Examples of LFE elements

37. Thermal mass measurementCapillaryprinciple

38. Thermal mass measurementCapillaryprinciple Advantages - Wetted materials: 316SS + O-rings (other materials possible, metal seal possible)- Compatible with most gasses- Calibration with air and conversion to other gasses possible- Established, lots of manufacturers.- 1 sccm till 5600 NLPM possible (Mostly used up to 1000 NLPM)- Up to 700 Bar possible Disadvantages - Lots of bad manufacturers (Drift, temp comp problems, etc)- Very sensitive for liquid and pollution- Expensive, difficult to manufacture them properly.

39. Thermal mass measurement Thermal profile: on a silicone MEMS or CMOS chipheatisintroducedintothe medium withconstantheatingoutput. In thepresence of flow, temperaturesensorsarrangedsymmetricallybefore and aftertheheatingsystemdetect a shift in thetemperatureprofiletowardsthesensordownstream of theheating system. Ifthereis no flowbothsensingelementsmeasurethe same temperature.

40. Delta-T temperatureof medium after heating temperatureof medium beforeheating Thermal mass measurement T1 T1

41. Thermal mass measurement Advantages: • Mainlyforgases • Indirect mass measurement (medium-dependent) • No movingparts • High precision • Independent offlowprofile • Fast, dynamicmeasurement Disadvantages: • Medium-dependent • Susceptibletosoiling • Severalwettedmaterials • Limited to non-corrosivegasses