Flowmeters illustration

When a bluff body is interspersed in a fluid stream, the flow is split into two parts. The boundary layer (see Chapter 11) which forms over the surface of the obstruction develops instabilities and vortices are formed and then shed successively from alternate sides of the body, giving rise to what is known as a von Karman vortex street. This process sets up regular pressure variations downstream from the obstruction whose frequency is proportional to the fluid velocity, as shown by Strouai. 9. Vortex flowmeters are very versatile and can be used with almost any fluid — gases, liquids and multi-phase fluids. The operation of the vortex meter, illustrated in Figure 6.27, is described in more detail in Volume 3, by Gjnesi(8) and in a publication by a commercial manufacturer, Endress and Hauser.10 ... 

Venturi tube flowmeters are devices used to measure fluid speeds in pipes. Figure 5.11 illustrates the general construction of a Venturi tube. These are very simple devices that consist of a middle section with a small diameter connected on both ends to larger diameter sections via smooth transitions in order to prevent turbulence. A U-tube containing a fluid of known density connects the large and small diameter tubes. The U-tube is a manometer, and we can use it to measure differences in pressure. 

The oldest and simplest methods of flow measurement are the various tagging techniques where a portion of the flow stream is tagged at some upstream point and the flow rate is determined by transit time flow measurement (TTFM) over some distance. As illustrated in Figure 3.65, any measurable process variable can be used to build a correlation flowmeter. Flow velocity is obtained by dividing the distance (between the identical pair of detectors) by the transit time. In recent years, the required electronic comput-... 

The liquid turbine meter is one of the most accurate meters having the highest rangeability, and can handle practically any pressure and extremely high and low temperatures. Their capacities are listed in Table 3.92, and their installation is illustrated in Figure 3.93. Turbine flowmeters in gas service are similar but designed for higher velocity and lower torque. 

Groszek (1966) early developed a simple flow-through adsorption calorimeter, which is somewhat similar to a differential thermal analysis (DTA) system (because of its single-point temperature detector) and is therefore well suited for the detection of thermal effects and for screening experiments. To obtain meaningful results requires more sophisticated equipment, however. A heat flowmeter microcalorimeter is normally used for this purpose. Such a microcalorimeter, especially designed for liquid-flow adsorption and for the complementary determination of AmitH, is illustrated in Figure 5.18. 

Problems at the end of this chapter illustrate the calibration and use of both types of flowmeters. 

Density is a frequently needed physical property of a process fluid. For example, engineers often know volumetric flow rates (F) of process streams from flowmeter readings but need to know mass flow rates m) or molar flow rates (h) for material balance calculations. The factor needed to calculate m or h from V is the density of the stream. This chapter illustrates the uses of both tabulated data and estimation formulas for calculating densities. Section 5.1 concerns solids and liquids Section 5.2 covers ideal gases, gases for which the ideal gas equation of state (PV - nRT) is a good approximation and Section 5.3 extends the discussion to nonideal gases. 

Activation of carbon is an art the significance of this concept is illustrated in an analogy namely, pyrometers, flowmeters, heaters, burners, and other tools for activation are analogous to orchestral instruments in that both need performers and a guiding score to make them effective. 

A coal slurry flow is a practical mixed-phase flow that requires close monitoring to ensure safe and efficient transport of the coal slurry. In addition to the flow rate measurement, detection of gas bubbles and settling of solids is equally important in coal slurry lines. In this section, we will describe a cross-correlation flowmeter that can reliably measure coal slurry flow rates over wide ranges of coal concentration and flow velocity. We will also illustrate how the flowmeter can detect settling of solids and recognize the presence of gas bubbles. Both laboratory and pilot plant flow tests are included. 

To illustrate density measurement by capacitive methods, the performance of the ANL capacitive mass flowmeter is described. Instrument evaluation tests were conducted at the ANL Solid/Liquid Test Facility (SLTF), shown schematically in Fig. 6.19. The SLTF was designed as a specialized instrument-testing and calibration-loop facility for various liquid and liquid/solid media. The facility can provide volumetric flow rates that range from 0 to 10 L/s and flow speeds up to 6 m/s in 2-in. Schedule 40 pipe. It is equipped with an acoustic cross-correlation flowmeter, a PNA system to... 

OFC) S - flow straightener R - resistance plate F - flowmeter P - magnetic drive pump Lwet - wetting length, (b) Schematic illustration of the ellipsometer L - He-Ne laser P - polarizer Q -quarterwave plate BM - birefringence modulator Gg - Brewster angle A - analyser PMT - photomultiplier tube. Reprinted with permission from [7a]. (1997) Elsevier. 

Figure 2.16 illustrates the principle of operation of a magnetic flowmeter. 

In the bubble gauge approach illustrated in Figure 9.15, a highly sensitive mass flowmeter (the term bubble gage test comes from a type of highly sensitivity mass flowmeter used for this purpose) is used to measure the crossover flow. A gas-phase pressure difference can be imposed across the anode and cathode to increase the crossover flow for ease of measurement and comparison. The inlet on the nonpressurized side is also closed, and a flowmeter on the nonpressurized side is used to measure the outgoing flow rate, which is the crossover flow. 

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