16 - Flow measurement

Abstract

This chapter discusses the rate at which fluid flows through a closed pipe and how it can be quantified by either measuring the mass flow rate or measuring the volume flow rate. The method used to measure mass flow rate is largely determined by whether the measured quantity is in a solid, liquid, or gaseous state. Conveyor-based methods are concerned with the measurement of the flow of solids that are in the form of small particles. The Coriolis flowmeter is primarily used to measure the mass flow rate of liquids, although it has been successfully used in some gas-flow measurement applications. Thermal mass flowmeters are primarily used to measure the flow rate of gases. The principle of operation is to direct the flowing material past a heated element. Volume flow rate is an appropriate way of quantifying the flow of all materials that are in a gaseous, liquid, or semi-liquid slurry form, where solid particles are suspended in a liquid host, although measurement accuracy is inferior to mass flow measurement. The gate meter consists of a spring-loaded, hinged flap mounted at right angles to the direction of fluid flow in the fluid-carrying pipe. All the usual benefits associated with intelligent instruments are applicable to most types of flowmeter. Indeed, all types of mass flowmeter routinely have intelligence as an integral part of the instrument. The number of relevant factors to be considered when specifying a flowmeter for a particular application is very large.