subject: Types Of Flowmeters Used Within The Processing Industry [print this page] The first person to help people understand how flow works was the Swiss physicist Daniel Bernoulli with the introduction of the concept of energy conservation with fluid flows in his published works, 'Hydrodynamica' in 1783. This entailed his idea on how there was an increase with the velocity of a fluids flow, along with the increase in kinetic energy and a decrease in static energy. Since then, a number of liquid flow measurement devices have been developed. Vortex meters, electromagnetic flowmeters, ultrasonic flowmeters, and Doppler varieties consist of some examples.
With many liquid flow measurement instruments, the flow rates are determined by interpreting measurement data recorded off the variations found with the liquids kinetic energy or velocity. Many times, the velocity depends on the amount of pressure differential used while forcing the liquid through the conduit or pipe. Due to already knowing the cross-sectional area, the average velocity relates to the flow rate. The liquids density and viscosity affect the liquids flow rate.
In addition, the friction caused from the liquids contact with the pipe additionally affects the liquid flow rates. By using a positive displacement flowmeter, direct measurements of the liquids flows achieved. One reason for this, relates to how it divides the liquid into increments as it moves along. The use of electronic or mechanical techniques helps with counting the accumulation of the measured increments in order to determine the total flow.
The Reynolds Number refers to a dimensionless unit referenced as the ration of liquids inertial forces in comparison to its drag forces. This tends to affect the performance of flowmeters. Turbulent and laminar flow refer to the two types of flows common within liquid flow measurement operations. The most common type encountered within most applications is turbulent flow.
Usually, laminar flows observed with viscous liquids with an R-value below 2000. Either a turbulent or a laminar flow may present during the transition period between both levels. Flowmeters tend to have a classification according to mechanical, differential pressure, electronic, and mass flow meters. Electronic flowmeters further include vortex meters, electromagnetic meters, as well as ultrasonic meters. Some common uses include processing environments such as power plants, as well as within other industrial plants used for the manufacturing of goods.
Vortex Meters
Vortex meters employ the naturally occurring phenomenon triggered by the flow of liquid around a bluff object. Vortices or eddies shed one after the other, subsequent to that object. The vortex-shedding rate, directly relates to the amount of velocity presented within the liquid flow going through the meter.
Three main parts comprise the vortex meter. This entails the sensor used to detect the presence of a vortex and the strut mounted across the flowmeters bore, as well as the bluff body. Vortex meters work identically well with taking measurements with the flow rate, as well as the flow total. However, vortex meters do not do well with high viscosity liquids or slurries.
Electromagnetic Flowmeter
The electromagnetic flowmeter works off the principle of Faraday's law of electromagnetic induction. These types of meters only have the capacity to detect the flow of conductive fluids only. The meters design consists of a non-magnetic pipe lined with insulating materials, as well as a pair of magnetic coils and electrodes in order to penetrate the pipe and its lining. Overall, a magnetic flowmeter has the capacity to detect the flow of viscous, corrosive, multi-phase, and clean types of liquids.
Ultrasonic flowmeter
With an ultrasonic flowmeter, the amount of speed at which the sound transmits within a fluid, depends on the fluid density. When the fluids density remains constant, the time of ultrasonic passage known as reflections can determine the fluids velocity. The ultrasonic meter further breaks down to include a Doppler meter, in addition to a transit meter.
