Flow meters types

Enough space must be available to properly service the flow meter and to install any straight lengths of upstream and downstream pipe recommended by the manufacturer for use with the meter. Close-coupled fittings such as elbows or reducers tend to distort the velocity profile and can cause errors in a manner similar to those introduced by laminar flow. The amount of straight pipe required depends on the flow meter type. For the typical case of an orifice plate, piping requirements are normally Hsted in terms of the P or orifice/pipe bore ratio as shown in Table 1 (1) (see Piping systems). 

Figure 8.14 shows some commonly used flow meters. Dolenc [23] reviews these flow-meter types in addition to other types. The meters in Figure 8.14 are divided into two classes the variable-head meters, which are the orifice, venturi. 

Wellhead equipment layout for sand coking in the bottomhole zone is shown on Fig. 89. A wellhead shut-in vdve is installed to seal off the well when necessary also a specially-designed lubricator provided with cable line packer is used so that the heater can be lowered and raised. To measure the amount of air injected, flow meter type DP-430 can be employed. Several electrical measurement instruments, such as the potentiometer and megohmmeter are also necessary. 

Fig. 14. OxyTech/Uhde HU-type cell a, cell bottom b, cathode c, anode d, cell cover e, bus bars f, brine level gauge g, brine flow meter h, bypass...

An outstanding advantage of common differential pressure meters is the existence of extensive tables of discharge coefficients ia terms of beta ratio and Reynolds numbers (1,4). These tables, based on historic data, are generally regarded as accurate to within 1—5% depending on the meter type, the beta ratio, the Reynolds number, and the care taken ia manufacture. Improved accuracy can be obtained by miming an actual flow caUbration on the device. 

La.mina.r Flow Elements. Each of the previously discussed differential-pressure meters exhibits a square root relationship between differential pressure and flow there is one type that does not. Laminar flow meters use a series of capillary tubes, roUed metal, or sintered elements to divide the flow conduit into innumerable small passages. These passages are made small enough that the Reynolds number in each is kept below 2000 for all operating conditions. Under these conditions, the pressure drop is a measure of the viscous drag and is linear with flow rate as shown by the PoiseuiHe equation for capilary flow ... 

Coriolis-Type Flow Meters. In CorioHs-type flow meters the fluid passes through a flow tube being electromechanically vibrated at its natural frequency. The fluid is first accelerated as it moves toward the point of peak vibration ampHtude and is then decelerated as it moves from the point of peak ampHtude. This creates a force on the inlet side of the tube in resistance to the acceleration and an opposite force on the outlet side resisting the deceleration. The result of these forces is an angular deflection or twisting of the flow tube that is directly proportional to the mass flow rate through the tube. 

Differential-Temperature Thermal Flow Meters. Meters of this type inject heat into the fluid and measure the resulting temperature rise or, alternatively, the amount of power required to maintain a constant temperature differential. The power required to raise the temperature of a flowing stream by an amount AT is given by the relation ... 

The firing controls that best ensure an air-rich mixture are often referred to as metering type controls, because gas flow and air flow are metered, thus the fuel-air ratio is controlled. The fuel-air ratio is the most important factor for safe, economical firing, so it is better to control it directly. Do not settle for low budget controllers that... 

Because a variety of meters are oommerdally available, the nurse explains about the type of meter that will be used, how often the peak flow should be checked, and the ranges for the readings along with instructions on what to do for each range. The nurse uses the following steps to instruct the patient on the use of the peak flow meter ... 

This equation defines the flow coefficient, Cv. Here, SG is the fluid specific gravity (relative to water), pw is the density of water, and hv is the head loss across the valve. The last form of Eq. (10-29) applies only for units of Q in gpm and hv in ft. Although Eq. (10-29) is similar to the flow equation for flow meters, the flow coefficient Cv is not dimensionless, as are the flow meter discharge coefficient and the loss coefficient (Af), but has dimensions of [L3][L/M]1/2. The value of Cv is thus different for each valve and also varies with the valve opening (or stem travel) for a given valve. Values for the valve Cv are determined by the manufacturer from measurements on each valve type. Because they are not dimensionless, the values will depend upon the specific units used for the quantities in Eq. (10-29). More specifically, the normal engineering (inconsistent) units of Cv are gpm/ (psi)1/2. [If the fluid density were included in Eq. (10-29) instead of SG, the dimensions of Cv would be L2, which follows from the inclusion of the effective valve flow area in the definition of Cv]. The reference fluid for the density is water for liquids and air for gases. 

The Doppler effect is used in practice to visualize directional blood flow on ultrasound, to estimate cardiac output and in some types of flow meter. 

The mass flow rates of air and fuel were measured with a set of float-type flow meters to a precision of 1%, and the overall equivalence ratio was determined with an uncertainty of less than 2%. The swirl number of the second-flow arrangement was defined at the exit of the swirler as... 

Two main types of volumetric filler exist. In the first type, a predetermined volume of liquid can be dosed using either a magnetic inductive volumetric flow meter or a mass flow meter. Alternatively, measuring cylinders can be used that incorporate a level probe. The product is fed to a set level in the metering cylinder, at which point the flow valve is closed off from the supply tank. A typical can filler operating at 1,500 cans of 330 ml capacity per minute will fill as per the supply contract within 2.5 ml. However, a standard deviation for a volumetric filler as low as 0.58 ml has been quoted. As with the probe filler, these fillers are fitted with electro-pneumatic valves, enabling accurate control of the... 

A. Flow Measurement by Displacement. A variety of flow meter designs are based on the positive displacement of a small amount of easily visualized material which does not alter the flow rate. A simple and easily constructed mass flow meter of this type, the soap-film meter, is based on timing the displacement of a soap film up a buret tube (Fig. 7.11). This type of flow meter is often placed at the exit of a gas chromatograph or small flow reactor. It is very... 

Pig. 7.13. Schematic of a mass flow meter. The flow is proportional to (T2 — Tt)1. This type of meter is often employed in an electrically controlled flow regulator. T, and T2 are temperature sensors H is a heater. 

Head flow meters operate on the principle of placing a restriction in the line to cause a pressure drop. The differential pressure which is caused by the head is measured and converted to a flow measurement. The basic construction of various types of head flow detectors is summarized below. 

Two other types of mechanical flow meters which can be used are the area flow and displacement meters. In addition, there exists much more sophisticated techniques for measurement offlow rate than use of differential pressure devices, such as anemometry, magnetic, and ultrasonic. 

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