Introduction to Instrumentation Sensors and Process Control. The accurate measurement of fluid flow is very important in many industrial appli- cations. Optimum performance of many processes requires specific flow rates. Thecost of many liquids and gases are based on the measured flow through a pipeline,making it necessary for accounting purposes to accurately measure and control therate of flow. This chapter discusses the basic terms, formulas, and techniques usedin flow measurements and flow instrumentation. Highly accurate and rugged flowdevices have now been developed and are commercially available. Developments intechnology are continually improving measurement devices . However, onesingle flow device is not suitable for all applications, and careful selection isrequired. At low flow rates, fluids have a laminar flow characteristic. As the flow rateincreases, the laminar flow starts to break up and becomes turbulent. The speed ofthe liquid in a fluid flow varies across the flow. Where the fluid is in contact with theconstraining walls (the boundary layer), the velocity of the liquid particles is virtu- ally zero, while in the center of the flow, the liquid particles have the maximumvelocity. Thus, the average rate of flow is used in flow calculations. The units ofvelocity are normally feet per second (ft/s), or meters per second (m/s). In a liquid,the fluid particles tend to move smoothly in layers with laminar flow, as shown in. Figure 9. 1(a). The velocity of the particles across the liquid takes a parabolic shape. With turbulent flow, the particles no longer flow smoothly in layers, and turbu- lence, or a rolling effect, occurs. This is shown in Figure 9.
Note also the flat- tening of the velocity profile. Flowcan be considered to be laminar, turbulent, or a combination of both. Osborne. Reynolds observed in 1. Instrumentation Process Control PPT 110 The Objective MAINTAIN THE PROCESS AND THE ELEMENTS OF THE PROCESS WITHIN WELL-DEFINED LIMITS OF VARIATION Process Control Process Control Processing Steps Automatically controlled. Process Control Instrumentation Technology - Curtis D. Johnson.pdf - Ebook download as PDF File (.pdf) or read book online. If the Reynolds number(R) for the flow in a pipe is equal toor less than 2,0. If the Reynolds number ranges from. Process Control Instrumentation Technology - Curtis D. Johnson. pdf. Get the full title to continue reading from where you left off, or restart the preview.
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