PRESENTATION ON DEVICES FOR MEASUREMENT OF

FLUID PARAMETRES

By Nitushmita BarmanMEB14009

MECHANICAL ENGINEERING DEPARTMENT

*Need of measurement of fluid parametres

Accurate measurement in a flowing medium is always desired in many applications.

The basic approach of the given measurement technique depends on the :

-flowing medium (liquid/gas)-nature of the flow (laminar/turbulent)- steady/unsteadiness

PARAMETERS

VISCOSITY VELOCITY PRESSURE TEMPERATURE DISCHARGE

*PARAMETER : VISCOSITY

VISCOMETER

Rotating CylinderFalling Sphere Capillary TubeEfflux

Saybolt Redwood Engler

*Efflux viscometer*Efflux cup viscometers are most commonly used for

fieldwork to measure the viscosity of oils, syrups, varnish, paints and Bitumen emulsions.

*The testing procedure : efflux time of a specified volume of fluid is measured through fixed orifice at the bottom of a cup to represent the viscosity of the fluid. Since the viscosity of Newtonian liquid are independent of dimensions of viscometer used, it is possible to convert the efflux times to kinematic viscosities by conversion charts or by formulas suggested by the equipment manufacturers.

Saybolt Viscometer Redwood Viscometer Engler Viscometer

TYPES OF EFFLUX VISCOMETER

*Capillary tube viscometer* This type of viscometer is based on

laminar flow through a circular pipe. *It has a circular tube attached horizontally

to a vessel filled with a liquid whose viscosity has to be measured.

*Falling Sphere Viscometer*It consists of a long container of constant

area filled with a liquid whose viscosity has to be measured. Since the viscosity depends strongly with the temperature, so this container is kept in a constant temperature bath

*Rotating Cylinder*It consists of two co-axial cylinders

suspended coaxially*The narrow annular space between the

cylinders is filled with a liquid for which the viscosity needs to be measured

Parameter : Velocity*Velocity measurement devices can be the following

types: 1. Velocity map using Pitot tube and Pitot static tube (Based on fluid mechanics principles) 2. Hot wire anemometer (Thermal effect of flow) 3.Doppler Velocimeter (Doppler effect due to scattering of waves by movinng particle) 4. Time of Flight Velocimeter (Based on time of travel of sound wave through a moving medium)

The pitot tube are one the most used (and cheapest) ways to measure fluid flow, especially in air applications like ventilation and HVAC systems, even used in airplane for speed measurment.

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PITOT TUBE AND PITOT STATIC TUBE

Thermal anemometry is the most common method used to measure instantaneous fluid velocity. The technique depends on the convective heat loss to the surrounding fluid from an electrically heated sensing element or probe.

The operating mode of hot wire anemometer is of two types: -constant current mode -constant voltage mode

*HOT WIRE ANEMOMETER

-This method of velocity measurement requires the presence of scattering particles in the flow. -The Doppler effect is the basis for the measurement.

*DOPPLER VELOCIMETER:

* Time of flight refers to the time it takes an acoustic beam to travel through a certain length in a moving medium. Since the motion of the medium affects the time of flight it is possible to use this as a means of measuring the velocityof the medium.

*TIME OF FLIGHT VELOCIMETER:

*Parameter : PressureThe fluid pressure is usually measured with reference to

standard atmosphere (i.e. 760mm of mercury/101.325 kPa)The pressure measuring devices mostly employed in fluid systems are generally grouped under three categories :

ManometerPitot TubeBourdon Gauge

*Manometer*The height of the liquid in a manometer is

directly proportional to the hydrostatic pressure.The three major types of manometers are: - manometer

differential Sealed-end Open-end

Pitot tube*Besides measuring velocity, pitot tubes also measure

pressure.

*Placement of holes on the pitot tube greatly affects the type of pressure to be measured. For example, the schematic drawing below shows the pitot tube measuring both static and total pressure.

Bourdon Gauge*Simplicity and small size makes the bourdon gauge*The bourdon pressure gauge is very common and probably

the most recognizable piece of pressure measuring equipment. Below are two views of a Bourdon gauge after it has been taken out of its casing. a popular pressure measuring device.

-Temperature is the measure of the average internal energy possessed by the molecules of a substance.*Types of temperature measurement device :

- Thermometer- Thermocouple- RTD- Thermistor

PARAMETER:TEMPARATURE

THERMOMETER*A thermometer is easy to use in the home and in

the laboratory.

THERMOCOUPLE*Thermocouples, also called thermoelectric couples,

are the most common type of temperature sensors in the chemical process industry. They use voltage to measure differences in temperature

RESISTANCE TEMPERATURE DETECTOR (RTD)*Resistance temperature detectors are the second most widely

used temperature sensor device in the chemical process industry behind thermocouples. Like thermistors, RTDs work by measuring a change in resistance with temperature.

THERMISTOR*Thermistors are made of materials whose electrical resistance

changes with temperature. They are very sensitive and accuracy is usually limited only by the readout device.

* A major requirement in application areas of fluid mechanics is the determination of flow rates and with respect to incompressible flows, they are called as flow metering.

CLASSIFICATION: Orifice meter

Venturimeter

Rotameter

Elbowmeter

*PARAMETER:FLOW RATE OR DISCHARGE

* With an orifice plate, the fluid flow is measured through the difference in pressure from the upstream side to the downstream side of a partially obstructed pipe.

*ORIFICEMETER:

VENTURIMETER:Venturi tube flowmeter is often used in applications where it's necessary with higher TurnDown Rates, or lower pressure drops, than the orifice plate can provide.

* ELBOWMETER:

*ROTAMETER:-The rotameter consists of a vertically oriented glass (or plastic) tube with a larger end at the top, and a metering float which is free to move within the tube

-An elbow meter is a pipe with a right-angle bend, and flow rate is gauged by sensors that measure the difference in pressure between the inner and outer angle of the bend.

*DIFFERENCE BETWEEN ORIFICE AND MOUTHPIECE FLOW ORIFICE FLOW MOUTHPIECE

FLOW Fluid is flowing through the small opening of any cross section on the side or at the bottom of the tank.

Fluid is flowing through a short length of a pipe which is two or three times its diameter in length,fitted in a tank containing the fluid which is called mouthpiece.

An orifice is a small aperture through which the fluid passes. The liquid from a tank is usually discharged through a small orifice at its side.

The discharge through an orifice is increased by fitting a short length of pipe to the outside known as mouthpiece.

Since the dimension of the orifice is to small so,flow through orifice is very small.

Dimension of mouthpiece is comparatively bigger than orifice.so,flow through mouthpiece is quiet large

*DIFFERENCE BETWEEN NOTCHES AND WEIRS FLOW

NOTCHES FLOW WEIRS FLOW

A notch may be defined as an opening in one side of a tank or a reservoir, like a large orifice, with the upstream liquid level below the top edge of the opening.and the flowing of the fluid is called notches flow.

A structure, used to dam up a stream or river, over which the water flows, is called a weir and th flow is called weirs flow.

can be found in narrow sections of rivers or in the lower ranges of the dams

In areas near dams one can see the use of V-shaped, rectangular notches

the notch of a small size the weir is of a bigger one.

a notch is usually made in a plate

a weirs is made of masonry or concrete.

*THANK YOU