UNDERSTANDING DIFFERENT FLOW METERS BY B.Raveendra CHEMICAL ENGINEERING GMRIT ,RAJAM

CONTENTS INTODUCTION VELOCITY FLOW METER INFERENTIAL FLOW METERS POSITIVE DISPLACEMENT METERS: DIRECT MASS FLOW MEASUREMENT:

INTODUCTION: one of the most important measurements in the chemical process industries (CPI) is rate of flow. Flow rate can be important to measure, and infect can be critical to measure ,thought a process from dosing components into a reactor to material transfer in between process steps, to discharging products at the end Flow metering technologies fall into 4 classification Velocity flow meter 2) inferential flow meter 3) positive displacement meter 4) mass flow meter

Velocity flow meter Many kinds of flow meters sense a fluids average velocity through a pipe. LAMINAR AND TURBULENT FLOW PROFILES :- When specifying velocity meters in chemical engineers must be concerned with the fluids velocity profile. In this case, the fluid velocity at the walls closely matches the fluid velocity at center and at all points in between. The velocity at any point is the average velocity. depending on the pipe diameter and the fluids density, viscocity, and momentum, the flow velocity with in a pipe can vary significantly between the pipe wall and its center.

PIPE GEOMETRY PLAYS A ROLE: Manufacturers will specify the length of straight pipe upstream and down stream of velocity flow meter for achieving high geometries in a chemical plant The flow meter may have to be located near an elbow,tee,valve or change in pipe diameter. In this case the flow will not be fully developed and results in a distorting profile .Various flow straightening devices installed upstream of the flow meter SOME VELOCITY FLOW METER : Electromagnetic flow meters: Vortex meter Swirl meters Turbine meters Ultrasonic meters

Electromagnetic flow meters Vortex meter Swirl meters Turbine meters:

Inferential flow meters Ultrasonic meters Inferential flow meters Differential pressure: Most of these flow measurement devices depend on three principles. with or without the restrictions in a pipe, the overall flow rate remains the same, Second the fluid flow velocity through the restriction must increase. Third the increased kinetic energy comes at the expenses of fluid pressure (potential pressure )

Rotameter. Target meters:

Flow meter elements based on differential pressure measurements Orifice plate: An orifice plate is a thin plate with a hole in the middle. It is usually placed in a pipe in which fluid flows. When the fluid reaches the orifice plate, with the hole in the middle, the fluid is forced to converge to go through the small hole; the point of maximum convergence actually occurs shortly downstream of the physical orifice,

Venturi meters: Venturi meters: The Venturi effect is a jet effect; as with a funnel the velocity of the fluid increases as the cross sectional area decreases, with the static pressure correspondingly decreasing. The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe.

Wedge Nozzle Pitot tube Flow tubes

Positive displacement meters: Positive displacement flow meters are true volumetric -flow devices measuring the actual fluid volume that passes through a meter body. it can can apply these flow meters to a wide range of non-abrasive fluids, including high viscosity fluids. Positive displacement flow meters are not suitable for applications that include solids, entrained to install and maintain having many moving parts. The pressure drop across these meters is high.

Direct mass flow measurement: two kinds of flow meters directly measure mass rates of fluids flow 1) coriolis flow meters for liquids and gases 2) thermal flow meters of gases .chemical process thermal flow meters coriolis flow meters

CONCLUSION: Evaluating the uncertainties and comparing uncertainties in the high and low flows found that the higher flow rates show more uncertainties than the lower flow rates Every calibration curve was linear except for the Venturi and Orifice meters. This is because of the second order equations needed to solve for the flow rate Turbine flow meters are first order. The Turbine flow meter calibration from lab is similar when compared to that of the manufactured calibration, but differences are still present. This can be explained by the fluid that was used to calibrate the meter.

Conclusion: Documented Accuracy Wide Range Energy Efficient B C D E F G H Documented Accuracy Wide Range Energy Efficient Negligible Installation Effect Adaptable To Gas Flow Field Certifiable Stable Signal Insensitive to Aging Experienced Manufacturer Use on Solids Bearings Fluids A. Classical Venturi B. Flow Tube C. Averaging Pitot D. Orifice plate E. Flow Nozzle F. Magnetic Flow Meter G. Sonic Flow Meter H. Doppler Flow Meter