FLOW MEASUREMENT INC 331 Industrial process measurement PDF Free Download

FLOW MEASUREMENT INC 331 Industrial process measurement 2018 1

TABLE OF CONTENTS A. INTRODUCTION B. LOCAL FLOW MEASUREMENT B.1 Particle Image Velocimetry (PIV) B.2 Laser doppler anemometry (LDA) B.3 Hot-wire and Hot film anemometer C. GROSS VOLUME FLOW MEASUREMENT C.1 Differential Pressure flowmeters C.2 Variable-Area flowmeters C.3 Magnetic flowmeters C.4 Turbine flowmeters C.5 Oscillatory flowmeters C.6 Ultrasonic flowmeters C.7 Positive Displacement flowmeters C.8 Target flowmeters C.9 Open-channel flowmeters (no lecture) D. GROSS MASS FLOW MEASUREMENT D.1 The inferential mass flow measurement D.2 Coriolis flowmeter D.3 Thermal mass flowmeter E. METER SELECTION 2

PART A. INTRODUCTION 3

Flow rates: 1. Volumetric flowrate (volume/time) Units: m 3 /s, LPM, GPM, etc 2. Mass flowrate (mass/time) Units: g/s, kg/min, etc 4

A. INTRODUCTION : Physical properties of fluid Temperature Pressure Density Viscosity Influence of viscosity on Flowmeter Newtonian and Non- Newtonian fluid Electrical conductivity Sonic conductivity 5

A. INTRODUCTION : Physical properties of fluid Images - Laminar/Turbulent Flows Laser - induced florescence image of an incompressible turbulent boundary layer Laminar flow Simulation of turbulent flow coming out of a tailpipe Turbulent flow SOURCE: http://www.engineering.uiowa.edu/~cfd/gallery/lim-turb.html 8

A. INTRODUCTION :Fundamentals of flow measurement 10

A. INTRODUCTION :Flow profile and piping effects Laminar flow profile Turbulent flow profile Effect of a single piping elbow on flow profile 11

A. INTRODUCTION :Flow profile and piping effects Flowmeters are often requirements for lengths of straight downstream piping between the flowmeter and disturbance. 12

PART B. LOCAL FLOW MEASUREMENT 13

B. LOCAL FLOW :Particle Image Velocimetry (PIV) 3D FlowMaster PIV system setup Reacting flowfield of a flat counterflow burner Source: http://www.lavision.de 14

B. LOCAL FLOW :Particle Image Velocimetry (PIV) FLOW MEASUREMENT Source: http://www.lavision.de 15

B. LOCAL FLOW :Particle Image Velocimetry (PIV) Source: http://www.dantecdynamics.com 16

B. LOCAL FLOW : Laser doppler anemometry (LDA) Invented by Yeh and Cummins in 1964 Velocity measurements in Fluid Dynamics (gas, liquid) Up to 3 velocity components Non-intrusive measurements (optical technique) Absolute measurement technique (no calibration required) Very high accuracy Very high spatial resolution due to small measurement volume Tracer particles are required Source: http://www.dantecdynamics.com 17

B. LOCAL FLOW : Laser doppler anemometry (LDA) Source: http://www.dantecdynamics.com 18

B. LOCAL FLOW : Laser doppler anemometry (LDA) Velocity = distance/time Flow with particles Signal Processor d (known) t (measured) Detector Time Bragg Cell Laser measuring volume backscattered light Source: http://www.dantecdynamics.com 19

B. LOCAL FLOW : Laser doppler anemometry (LDA) Laser Doppler Anemometry can be used to investigate propulsion efficiency and cavitation. Measurement in a test engine using Laser Doppler Anemometry. Source: AVL-List Austria 20

B. LOCAL FLOW : Hot-wire anemometer The Hot-Wire Anemometer is the most well known thermal anemometer, and measures a fluid velocity by noting the heat convected away by the fluid. The core of the anemometer is an exposed hot wire either heated up by a constant current or maintained at a constant temperature. The heat lost to fluid convection is a function of the fluid velocity. 21

B. LOCAL FLOW : Hot-wire anemometer Source: http://www.spiraxsarco.com 22

B. LOCAL FLOW :Multi-channel Hot-wire anemometer Source: http://www.dantecdynamics.com 23

PART C. GROSS VOLUME FLOW MEASUREMENT 24

C. GROSS VOLUME FLOW :Differential pressure flowmeter The most commonly used differential pressure flowmeter type are: Orifice Venturi Nozzle Averaging Pitot tube Wedge meter 25

C. GROSS VOLUME FLOW :Differential pressure flowmeter Pressure contour and velocity profiles Source: http://www.tecplot.com 26

C. GROSS VOLUME FLOW :Differential pressure flowmeter Source: http://flowlab.fluent.com/features/index.htm 27

C. GROSS VOLUME FLOW :Differential pressure flowmeter 28

C. GROSS VOLUME FLOW :Differential pressure flowmeter C.1.1 Orifice 29

C. GROSS VOLUME FLOW :Differential pressure flowmeter Orifice plate & differential pressure transmitter Source: http://www.spiraxsarco.com 30

C. GROSS VOLUME FLOW :Differential pressure flowmeter Compact Orifice & Installation 31

C. GROSS VOLUME FLOW :Differential pressure flowmeter C.1.2 Venturi A venture is a restriction with a relatively long passage with smooth entry and exit. It produces less permanent pressure loss than similar sized orifice but it is more expensive. It often used in dirty flow streams. 32

C. GROSS VOLUME FLOW :Differential pressure flowmeter C.1.3 Nozzle Flow nozzles have a smooth entry and shape exit. The permanent pressure loss pf a nozzle is of the same order as that of an orifice, but it can handle dirty and abrasive fluid better than and orifice can. It often used in steam service because of their rigidity, which makes them more stable at high temperature and velocities than orifice. 33

C. GROSS VOLUME FLOW :Differential pressure flowmeter Nozzle installation 34

C. GROSS VOLUME FLOW :Differential pressure flowmeter C.1.4 Averaging pitot tube 35

C. GROSS VOLUME FLOW :Differential pressure flowmeter C.1.5 Wedge meter 36

C. GROSS VOLUME FLOW :Differential pressure flowmeter Primary elements Orifice Venturi Nozzle Averaging Pitot tube Wedge meter Elbow Score Phase Condition Cryogenic Gas Liquid Steam Liquid Slurry : Recommended : Limited applicability Clean Dirty Clean Dirty Viscous Saturated Superheated Corrosive Abrasive Elbow 37

C. GROSS VOLUME FLOW :Variable-area flowmeter 38

C. GROSS VOLUME FLOW :Variable-area flowmeter 39

C. GROSS VOLUME FLOW :Variable-area flowmeter 40

C. GROSS VOLUME FLOW :Variable-area flowmeter 41

C. GROSS VOLUME FLOW :Variable-area flowmeter Score Phase Condition Gas Clean Liquid Gas Liquid Clean Open Channel Dirty Corrosive Steam Dirty Recommended Limited applicability Saturated 42

C. GROSS VOLUME FLOW :Magnetic flowmeter Magnetic flowmeters, also known as electromagnetic flowmeters or induction flowmeters, obtain the flow velocity by measuring the changes of induced voltage of the conductive fluid passing across a controlled magnetic field. Flangeless type 43

C. GROSS VOLUME FLOW :Magnetic flowmeter According to Faraday's law of electromagnetic induction: any change in the magnetic field with time induces an electric field perpendicular to the changing magnetic field: where E is the voltage of induced current, B is the external magnetic field, A is the corss section area of the coil, N is the number of turns of the coil, is the magnetic flux, and finally the negative sign indicates that the current induced will create another magnetic field opposing to the buildup of magnetic field in the coil based on Lenz's law. When applying the above equation to magnetic flowmeters, the number of turns N and the strength of the magnetic field B are fixed. The Faraday's law becomes where D is the distance between the two electrodes (the length of conductor), and V is the flow velocity. Source : www.efunda.com 44

C. GROSS VOLUME FLOW :Magnetic flowmeter Straight run upstream of well-designed magnetic flowmeter from the centre of meter for standard accuracy (1% rate): Inlet run: 3D-5D Outlet run: 2D Elbow,3D Pump,10D Control valve, 10D (should be located downstream of the flowmeter) 45

C. GROSS VOLUME FLOW :Magnetic flowmeter Score Phase Condition Liquid Clean Corrosive Dirty Viscous Slurry Abrasive Fibrous Liquid Non-Newtonian : Recommended : Limited applicability Open Channel 46

C. GROSS VOLUME FLOW :Turbine flowmeter 47

C. GROSS VOLUME FLOW :Turbine flowmeter 48

C. GROSS VOLUME FLOW :Turbine flowmeter Above figure is the cross-section of the turbine flowmeter. The blades start rotating at an angular speed, inside the pipeline. The magnetic pickoffs placed in the pipe body is the sensing element. As the paramagnetic blades cuts through the magnetic pickoff coil, its magnetic properties cause the magnetic field to deflect to accommodate its presence. This deflection causes to generate an irregular shaped voltage in the coil. The frequency of the pulse generated is directly proportional to the angular velocity of the turbine and thus proportional to the flow speed of the stream. 49 Reference: https://automationforum.in/t/flow-measurement-using-turbine-flowmeter/2886

Application: C. GROSS VOLUME FLOW :Turbine flowmeter Used in oil and gas wastewater, gas utility, chemical, power, food and beverage, aerospace, pharmaceutical, metals and mining, and pulp and paper industries. The turbine flowmeter cannot be used in higher magnitude flow because premature bearing wear and/or damage can occur.also cannot be used to measure very low flow rates due to rotor/bearing drag that slows the rotor. Advantages: Excellent rangeability Each electrical pulse generated is also proportional to a small incremental volume of flow. Can operate in wide range of temperature and pressure Easy to install, maintain and to calibrate Only a low pressure is dropped across the turbine. Disadvantages: Require constant back pressure to prevent cavitation Can not used to measure corrosive fluid, which will affect the blades May does not work properly for laminar flow measurement, which has higher viscosity. Very sensitive to fluid viscosity. Reference: https://automationforum.in/t/flow-measurement-using-turbine-flowmeter/2886 50

C. GROSS VOLUME FLOW :Turbine flowmeter 51

C. GROSS VOLUME FLOW :Turbine flowmeter Score Phase Condition Gas Liquid Liquid Clean Clean Corrosive : Recommended : Limited applicability Open Channel 52

C. GROSS VOLUME FLOW :Oscillatory flowmeter 53

C. GROSS VOLUME FLOW :Oscillatory flowmeter 54

C. GROSS VOLUME FLOW :Oscillatory flowmeter Vortex flowmeters, also know as vortex shedding flowmeters or oscillatory flowmeters, measure the vibrations of the downstream vortexes caused by the barrier placed in a moving stream. The vibrating frequency of vortex shedding can then be related to the velocity of flow. 55

C. GROSS VOLUME FLOW :Oscillatory flowmeter When a fluid flows steadily over an isolated cylindrical solid barrier and the Reynolds number is great than about 50, vortices are shed on the downstream side. The vortices trail behind the cylinder in two rolls, alternatively from the top or the bottom of the cylinder. This vortex trail is call the von Karman vortex street or Karman street after von Karman's 1912 mathematical description of the phenomenon. Reference: https://www.yokogawa.com/solutions/products-platforms/field-instruments/flow-meters/vortex-flow-meters/ Reference: http://www.aalborg.com/index.php/main_page/product_overview/id_product_overview/71 The frequency of vortex shedding is definite and is related to the Reynolds number (flow velocity, viscosity of fluid, and the diameter of the cylinder). The frequency of vortex shedding is the same as the vibrating frequency of the cylinder induced by the flow. 56

C. GROSS VOLUME FLOW :Oscillatory flowmeter Source: http://flowlab.fluent.com/features/index.htm 57

C. GROSS VOLUME FLOW :Oscillatory flowmeter 58

C. GROSS VOLUME FLOW :Oscillatory flowmeter Vortex Flowmeter Score Phase Condition Gas Clean Dirty Liquid Steam Clean Saturated Superheated Liquid Corrosive : Recommended : Limited applicability Dirty 59

C. GROSS VOLUME FLOW :Ultrasonic flowmeter Ultrasonic flow meters use sound waves to measure the flow rate of a fluid. There are 2 measuring concepts: transit time and doppler. Clean liquid Dirty liquid Transit ultrasonic flowmeter They send two ultrasonic signals across a pipe: one traveling with the flow and one traveling against the flow. The ultrasonic signal traveling with the flow travels faster than a signal traveling against the flow. The ultrasonic flowmeter measures the transit time of both signals. The difference between these two times is proportional to flow rate. 60

C. GROSS VOLUME FLOW :Ultrasonic flowmeter Downstream pulse transmit time can be expressed as td = L / (c + v cosφ) where td = downstream pulse transmission time L = distance between transceivers v = fluid flow velocity c = the velocity of sound in the fluid Downstream pulse transmit time can be expressed as tu = L / (c - v cosφ) where tu = upstream pulse transmission time Since the sound travels faster downstream than upstream, the difference can be expressed as t = td - tu = 2 v L cosφ / ( c2 - v2 cos2φ) = 2 v L cosφ / c2 (since v is very small compared to c) 61

Features Transit time of flight[clean liquid] Reading accuracy is as good as any typical magnetic flowmeter Measure down to low or zero flow Mobility 62

C. GROSS VOLUME FLOW :Ultrasonic flowmeter Doppler ultrasonic flowmeter Doppler flow meters transmit ultrasonic sound waves into the fluid. These waves are reflected off particles and bubbles in the fluid. The frequency change between the transmitted wave and the received wave can be used to measure the velocity of the fluid flow. 63

Doppler Effect The Doppler Effect Ultrasonic Flowmeter The Doppler Effect Ultrasonic Flowmeter use reflected ultrasonic sound to measure the fluid velocity. By measuring the frequency shift between the ultrasonic frequency source, the receiver, and the fluid carrier, the relative motion are measured. The resulting frequency shift is named the Doppler Effect. The fluid velocity can be expressed as v = c (fr - ft) / 2 ft cosφ where fr = received frequency ft = transmission frequency v = fluid flow velocity Φ = the relative angle between the transmitted ultrasonic beam and the fluid flow c = the velocity of sound in the fluid 64

C. GROSS VOLUME FLOW :Ultrasonic flowmeter Transit ultrasonic Doppler ultrasonic Score Phase Condition Score Phase Condition Gas Clean Gas Dirty Liquid Clean Liquid Corrosive Corrosive Dirty Dirty Open Channel Gas Dirty Gas Clean Liquid Open Channel Liquid Clean Viscous Viscous : Recommended : Limited applicability : Recommended : Limited applicability 65

C. GROSS VOLUME FLOW :Ultrasonic flowmeter 66

C. GROSS VOLUME FLOW :Positive Displacement flowmeter Positive displacement flowmeters, also know as PD meters, measure volumes of fluid flowing through by counting repeatedly the filling and discharging of known fixed volumes. The volume of the fluid that passes the chamber can be obtained by counting the number of passing parcels or equivalently the number rounds of the rotating/reciprocating mechanical device. The volume flow rate can be calculated from the revolution rate of the mechanical device. 67

C. GROSS VOLUME FLOW :Positive Displacement flowmeter Score Phase Condition Liquid Clean Viscous Liquid Corrosive Dirty : Recommended : Limited applicability 68

C. GROSS VOLUME FLOW : Target flowmeters The drag force F d is given by the drag equation of incompressible flow: where V is flow velocity, ρ is the density of the fluid, A is the projected area of the target, and C d is the drag coefficient to be determined experimentally based on the flow conditions and the geometry of the drag element. 69

C. GROSS VOLUME FLOW : Target flowmeters When the flow is turbulent the Reynolds number is large, and the drag coefficient Cd is approximately constant. This is the quadratic model of fluid resistance, in that the drag force is dependent on the square of the velocity 70

C. GROSS VOLUME FLOW : Target flowmeters Score Phase Condition Cryogenic Gas Clean Dirty Liquid Clean Dirty Viscous Steam Liquid Saturated Corrosive : Recommended : Limited applicability 71

PART D. GROSS MASS FLOW MEASUREMENT 72

D. GROSS MASS FLOW In Today s industrial applications there are commonly 3 ways to determine mass flow: The inferential mass flow measurement the application of microprocessor-based volumetric technology to conventional volumetric meters. Separate sensors response to velocity or momentum and pressure, temperature, etc. The Coriolis flowmeter, which measure mass flow directly. The thermal mass flowmeter, which determine mass flow by measuring heat dissipation between two points in pipeline. 73

D. GROSS MASS FLOW : Inferential mass flow measurement Flow meter Liquid Mass 74

D. GROSS MASS FLOW : Inferential mass flow measurement Flow meter gas Mass 75

D. GROSS MASS FLOW : Inferential mass flow measurement Flow meter Steam Mass 76

D. GROSS MASS FLOW :Coriolis mass flowmeter NO Flow: Parallel detection Mass Flow: Coriolist Twist 77

D. GROSS MASS FLOW :Coriolis mass flowmeter What is the Coriolis Principle? To some of us the Coriolis Principle is an exact science, but to most of us it is still a black art. Well, imagine a fluid flowing (at velocity V) in a rotating elastic tube as shown below. The fluid will deflect the tube. Further, consider a Mass M moving from the center to the edge of a rotating plate. This Mass M will take path B as shown below 78

D. GROSS MASS FLOW :Coriolis mass flowmeter 79

D. GROSS MASS FLOW :Coriolis mass flowmeter Score Phase Condition Liquid Clean Direct Mass Dirty Non-Newtonian Slurry Gas Liquid Slurry : Recommended : Limited applicability Viscous Abrasive Clean Dirty Corrosive Fibrous 80

D. GROSS MASS FLOW :Coriolis mass flowmeter Various configurations for Coriolis flowmeters 81

D. GROSS MASS FLOW :Thermal mass flowmeter 82

D. GROSS MASS FLOW :Thermal mass flowmeter The measurement principle operates by monitoring the cooling effect of a gas as it passes over a heated transducer. Gas flowing through the sensing section passes over two RTD transducers. One RTD is used conventionally as a temperature sensing device, while the other is used as a heater. 83

D. GROSS MASS FLOW :Thermal mass flowmeter The temperature transducer monitors the actual gas process temperature, while the self-heated transducer is maintained at a constant differential temperature (relative to the measured gas temperature) by varying the current through it. The greater the mass flow passing over the heated transducer, the greater the cooling effect, and current required to keep a constant differential temperature. The measured heater current is therefore a measure of the gas mass flowrate. 84

D. GROSS MASS FLOW :Thermal mass flowmeter Reference: https://sagemetering.com/applications/ 85

D. GROSS MASS FLOW :Thermal mass flowmeter Score Phase Condition Gas Gas Clean Dirty : Recommended : Limited applicability General purpose Thermal mass flowmeters SOURCE: http://www.sagemetering.com/ 86

Turn Down Turn Down or Turn down Ration describes the range of flow rates between maximum and minimum flow over which a flow meter will work satisfactorily within the accuracy limits and repeatability of tolerances specified by the manufacturer. Effective range and Rangeability are alternative terms used to describe meter turn down. It is very important to select a flow meter with sufficient range for the application. Failure to do this will introduce considerable errors especially at low flow rates. Selecting the right flow range requires a diligent and holistic study of the maximum, normal and minimum flow that is required for a given application. The turn down ratios of some common flow meters in use are given below: Flowmeter Type Turn Down or Operating Range Minimum Flow Orifice Plate 4:1 25% of Maximum flow Turbine 10:1 10% of Maximum flow Coriolis 80:1 1.25% of Maximum flow As shown in the table above, if we are using these flow meters to measure a given liquid in an application where the expected maximum flow rate is 2,400gpm then: For the Orifice plate meter, minimum flow = 25% of maximum flow = 600gpm. Since the turn down of the Orifice meter is 4:1, this means that at flow rates between 600gpm and 2,400gpm the flow meter can still meet its claimed or stated accuracy. However, at flow rates lower than 600gpm this flow meter cannot meet its stated specification, so large flow errors occur. At best, the recorded flows below 600gpm are inaccurate - at worst they are not recorded at all, and are lost. This problem of considerable errors at low flow rates due to insufficient turn down is particularly worst for differential pressure flow meters where flow is proportional to the square of pressure. For the Turbine meter, minimum flow = 10% of maximum flow = 240gpm For the Coriolis meter, minimum flow = 1.25% of maximum flow = 30gpm At flow rates below these for the turbine and Coriolis flow meters, the meters can no longer give accurate measurements. So it is important to do proper flow study for your application to enable you select a flow meter technology with the sufficient turn down to meet the range of flow rates expected for your application.

Rangeability Ratio of maximum operating capacity to minimum operating capacity within a specified tolerance and operating condition is a ratio of full span to smallest flow that can be measured with sufficient accuracy Example(1): it is assumed that the instrument has a specified accuracy of ±0.5% of Full Scale. If the limit on the acceptable performance is ±4% of reading then the rangeability of the instrument is limited to 8 to 1 (i.e. ±4% of reading accuracy occurs at 12.5% of full scale). However if an accuracy of ±5% of reading were acceptable, the rangeability of the instrument would be increased to 10 to 1. Example(2). One flowmeter might measure 20-100 lpm within 1% error of the actual flow rate, rangeability is 100/20 or 5:1. Imply:Instrument ability to measure the difference between low and high flow within the acceptable accuracy 88

Accuracy: % Full Scale vs. % Reading The accuracy (really inaccuracy) of mass flow instruments is specified in one of two ways, either accuracy as a percentage of full scale (% FS), or accuracy as a percentage of reading (% RD). If an instrument has accuracy specified as % FS then the error will have a fixed value no matter where the flow is in the flow range. Take, for example, an instrument calibrated for a flow of 100 l n /min with stated accuracy 1.0% of FS. At a flow of 100 l n /min (full scale) the error will be 1% of full scale, or +/- 1 l n /min. As the flow moves way from full scale the error will still be 1% FS (+/- 1 l n /min), so at a flow of 50 l n /min that error of +/- 1 l n /min becomes a larger percentage (+/- 2%) of flow. Going further away from full scale flow further increases the error as a percentage of flow; at a flow of 10 l n /min the +/- 1 l n /min error is +/- 10% of the flow. If, however, an instrument has accuracy specified as % RD then the error will always be the same percentage of the actual flow. Using the 100 l n /min instrument again as the example, but this time with a stated accuracy of 1% RD, at 10 l n /min of flow the error is only +/- 1% of the flow, better by 10 times. Note. l n /min (liter normal per minute) is a mass flow unit that works in units of volume Reference: https://www.massflow-online.com/faqs/accuracy-full-scale-vs-reading/ http://www.massflow-online.com/faqs/what-do-lnmin-lsmin-slm-and-sccm-stand-for/ 89

PART E. METER SELECTION 90

E. METER SELECTION 91

E. METER SELECTION Total or rate of flow Flowmeters categorized by applications 92