The Measurement of Fluid Flow
FLOW MEASUREMENT (Venturi meter, Orifice Plate and Rotameter)
OBJECTIVES To study the characteristics and applications of various flow measuring device (venturi meter & orifice plate). To calculate the volume flow rate of water from the pressure difference of both venturi and orifice devices. To compare between theoretical and actual volumetric flow rate through the discharge coefficient concept. To know how rotameter works.
INTRODUCTION The measurement of fluid flow is important in applications ranging from measurements of blood-flow rates in human artery to the measurement of liquid oxygen in a rocket. The selection of the proper instrument for a particular application is governed by many variables, including cost. Flow-rate-measurement devices frequently require accurate pressure and temperature measurements in order to calculate the output of the instrument. The most widely used flow metering principle involves placing a fixed area flow restriction of some type in the pipe or duct carrying the fluid. This flow restriction causes a pressure drop that varies with the flow rate. Thus, measurement of the pressure drop by means of a suitable differential-pressure pick up allows flow rate measurement. Each of the flow measurement devices inherently has its own advantages and disadvantages. Some of those instruments are: • The Venturi Meter In the venturi meter (shown in figure (1) below) the fluid is accelerated through a converging cone of angle 15-20° and the pressure difference between the upstream side of the cone and the throat is measured and provides the signal for the rate of flow.
Upstream pressure tap
Downstream pressure tap
Venturi Throat
Upstream Flow Figure (1) : The Venturi meter operation.
Downstream Flow
The fluid slows down in a cone with smaller angle (5-7°) where most of the kinetic energy is converted back to pressure energy. Because of the cone and the gradual reduction in the area there is no "vena contracta". The flow
OBJECTIVES To study the characteristics and applications of various flow measuring device (venturi meter & orifice plate). To calculate the volume flow rate of water from the pressure difference of both venturi and orifice devices. To compare between theoretical and actual volumetric flow rate through the discharge coefficient concept. To know how rotameter works.
INTRODUCTION The measurement of fluid flow is important in applications ranging from measurements of blood-flow rates in human artery to the measurement of liquid oxygen in a rocket. The selection of the proper instrument for a particular application is governed by many variables, including cost. Flow-rate-measurement devices frequently require accurate pressure and temperature measurements in order to calculate the output of the instrument. The most widely used flow metering principle involves placing a fixed area flow restriction of some type in the pipe or duct carrying the fluid. This flow restriction causes a pressure drop that varies with the flow rate. Thus, measurement of the pressure drop by means of a suitable differential-pressure pick up allows flow rate measurement. Each of the flow measurement devices inherently has its own advantages and disadvantages. Some of those instruments are: • The Venturi Meter In the venturi meter (shown in figure (1) below) the fluid is accelerated through a converging cone of angle 15-20° and the pressure difference between the upstream side of the cone and the throat is measured and provides the signal for the rate of flow.
Upstream pressure tap
Downstream pressure tap
Venturi Throat
Upstream Flow Figure (1) : The Venturi meter operation.
Downstream Flow
The fluid slows down in a cone with smaller angle (5-7°) where most of the kinetic energy is converted back to pressure energy. Because of the cone and the gradual reduction in the area there is no "vena contracta". The flow