FLOW MEASUREMENT. INC 102 Fundamental of Instrumentation and Process Control 2/ PDF Free Download

FLOW MEASUREMENT INC 102 Fundamental of Instrumentation and Process Control 2/2560

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 Coriolis flowmeter D.2 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 C. GROSS VOLUME FLOW MEASUREMENT 13

C. GROSS VOLUME FLOW :Differential pressure flowmeter The most commonly used differential pressure flowmeter type are: Orifice Venturi Nozzle Averaging Pitot tube Wedge meter 14

C. GROSS VOLUME FLOW :Differential pressure flowmeter Pressure contour and velocity profiles Source: http://www.tecplot.com 15

C. GROSS VOLUME FLOW :Differential pressure flowmeter Source: http://flowlab.fluent.com/features/index.htm 16

C. GROSS VOLUME FLOW :Differential pressure flowmeter 17

C. GROSS VOLUME FLOW :Differential pressure flowmeter C.1.1 Orifice 18

C. GROSS VOLUME FLOW :Differential pressure flowmeter Orifice plate & differential pressure transmitter Source: http://www.spiraxsarco.com 19

C. GROSS VOLUME FLOW :Differential pressure flowmeter Compact Orifice & Installation 20

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. 21

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. 22

C. GROSS VOLUME FLOW :Differential pressure flowmeter Nozzle installation 23

C. GROSS VOLUME FLOW :Differential pressure flowmeter C.1.4 Averaging pitot tube 24

C. GROSS VOLUME FLOW :Differential pressure flowmeter C.1.5 Wedge meter 25

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 26

C. GROSS VOLUME FLOW :Variable-area flowmeter 27

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 28

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 29

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 30

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) 31

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 32

C. GROSS VOLUME FLOW :Turbine flowmeter 33

C. GROSS VOLUME FLOW :Turbine flowmeter 34

C. GROSS VOLUME FLOW :Turbine flowmeter 35

C. GROSS VOLUME FLOW :Turbine flowmeter 36

C. GROSS VOLUME FLOW :Turbine flowmeter Score Phase Condition Gas Liquid Liquid Clean Clean Corrosive : Recommended : Limited applicability Open Channel 37

C. GROSS VOLUME FLOW :Oscillatory flowmeter 38

C. GROSS VOLUME FLOW :Oscillatory flowmeter 39

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. 40

C. GROSS VOLUME FLOW :Oscillatory flowmeter Source: http://flowlab.fluent.com/features/index.htm 41

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. 42

C. GROSS VOLUME FLOW :Oscillatory flowmeter 43

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 44

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. 45

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) 46

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 47

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. 48

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 49

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 50

C. GROSS VOLUME FLOW :Ultrasonic flowmeter 51

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. 52

C. GROSS VOLUME FLOW :Positive Displacement flowmeter Score Phase Condition Liquid Clean Viscous Liquid Corrosive Dirty : Recommended : Limited applicability 53

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. 54

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 55

C. GROSS VOLUME FLOW : Target flowmeters Score Phase Condition Cryogenic Gas Clean Dirty Liquid Clean Dirty Viscous Steam Liquid Saturated Corrosive : Recommended : Limited applicability 56

PART D. GROSS MASS FLOW MEASUREMENT 57

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. 58

D. GROSS MASS FLOW : Inferential mass flow measurement Flow meter Liquid Mass 59

D. GROSS MASS FLOW : Inferential mass flow measurement Flow meter gas Mass 60

D. GROSS MASS FLOW : Inferential mass flow measurement Flow meter Steam Mass 61

PART E. METER SELECTION 62

E. METER SELECTION 63

E. METER SELECTION Total or rate of flow Flowmeters categorized by applications 64

FLOW MEASUREMENT. INC 102 Fundamental of Instrumentation and Process Control 2/2560