Flow measurement volumetric

Measurement by Electromagnetic Effects. The magnetic flow meter is a device that measures the potential developed when an electrically conductive flow moves through an imposed magnetic field. The voltage developed is proportional to the volumetric flow rate of the fluid and the magnetic field strength. The process fluid sees only an empty pipe so that the device has a very low pressure drop. The device is useful for the measurement of slurries and other fluid systems where an accumulation of another phase could interfere with flow measurement by other devices. The meter must be installed in a section of pipe that is much less conductive than the fluid. This limits its appHcabiHty in many industrial situations. 

The flow that is shown in these figures is the instrument flow measured as m/s in the measuring tube. Multiplied with the flow cross-section of 5.59 cm, this gives the volumetric flow in the 2.67-cm diameter flow tube. Using a different catalyst basket or measuring tube will change this ratio. The volumetric flow is the same in the basket. Because the small basket has a 3.15 cm diameter and 7.79 cm cross-section, the linear velocity will be 5.59/7.79 = 0.72 fraction of that in the tube. 

If the mobile phase is a liquid, and can be considered incompressible, then the volume of the mobile phase eluted from the column, between the injection and the peak maximum, can be easily obtained from the product of the flow rate and the retention time. For more precise measurements, the volume of eluent can be directly measured volumetrically by means of a burette or other suitable volume measuring vessel that is placed at the end of the column. If the mobile phase is compressible, however, the volume of mobile phase that passes through the column, measured at the exit, will no longer represent the true retention volume, as the volume flow will increase continuously along the column as the pressure falls. This problem was solved by James and Martin [3], who derived a correction factor that allowed the actual retention volume to be calculated from the retention volume measured at the column outlet at atmospheric pressure, and a function of the inlet/outlet pressure ratio. This correction factor can be derived as follows. 

Flow Rate. The values for volumetric or mass flow rate measurement are often determined by measuring pressure difference across an orifice, nozzle, or venturi tube. Other flow measurement techniques include positive displacement meters, turbine flowmeters, and airflow-measuring hoods. 

An important application of Bernoulli s equation is in flow measurement, discussed in Chapter 8. When an incompressible fluid flows through a constriction such as the throat of the Venturi meter shown in Figure 8.5, by continuity the fluid velocity must increase and by Bernoulli s equation the pressure must fall. By measuring this change in pressure, the change in velocity can be determined and the volumetric flow rate calculated. 

In practice, the measured volumetric flow rate is always less than Q... 

Orifice meters, Venturi meters and flow nozzles measure volumetric flow rate Q or mean velocity u. In contrast the Pitot tube shown in a horizontal pipe in Figure 8.7 measures a point velocity v. Thus Pitot tubes can be used to obtain velocity profiles in either open or closed conduits. At point 2 in Figure 8.7 a small amount of fluid is brought to a standstill. Thus the combined head at point 2 is the pressure head P/( pg) plus the velocity head v2/(2g) if the potential head z at the centre of the horizontal pipe is arbitrarily taken to be zero. Since at point 3 fluid is not brought to a standstill, the head at point 3 is the pressure head only if points 2 and 3 are sufficiently close for them to be considered to have the same potential head... 

Although Pitot tubes are inexpensive and have negligible permanent head losses they are not widely used. They are highly sensitive to fouling, their required alignment is critical and they cannot measure volumetric flow rate Q or mean velocity u. The latter can be calculated from a single measurement only if the velocity distribution is known this can be found if the Pitot tube can be traversed across the flow. 

Variables Affecting Measurement Flow measurement methods may sense local fluid velocity, volumetric flow rate, total or cumulative volumetric flow (the integral of volumetric flow rate with respect to elapsed time), mass flow rate, and total mass flow. 

Although electrical measurements have confirmed the ionic nature of borate melts, viscous flow and volumetric studies clearly indicated their difference from liquid silicates. Shartsia and co-workers (4 ) have suggested that an equilibrium exists in the melt between BOj triangles and B04 Letrahedra, this being both temperature and composition dependent. The only ionic model for the borates is that of Bockris and Mellors (8) which... 

One class of flow measurement which is becoming of increasing importance (particularly in the form of sensors for control systems) is the monitoring of mass flow. This is rapidly superseding the measurement of volumetric flow—especially where it is required to determine accurately the transfer of large quantities of gas and liquid in the oil, gas and water industries. Two principal approaches are employed to measure mass flow. One is indirect and uses a combination of volumetric flow and density and the other is direct in that it involves the measurement of properties which are sensitive to variations in the mass rate of flow itself. 

There have been several different 3D-3C (or volumetric) PIV techniques for macro-scaled flow measurement. Among them, holographic PIV (HPIV), defocusing PIV (DPIV), and tomographic PIV (TPIV) are the three that inherently measure all the three components of velocity field in a 3D volume. Other PIV techniques available to obtain a 3D velocity field, such as scanning PIV, dynamic PIV, that are based on some indirect algorithms to reconstruct a 3D velocity field, will be mentioned in the later sections. 

PD gas meters measure volumetric flow by internally passing isolated volumes of gas in a process of successively filling and emptying compartments. This filling and emptying process is controlled by valves and is translated into rotary motion to operate a calibrated register or index that indicates the total volume of gas passed through the meter. 

Cross-correlation flowmeters in combination with concentration detectors are available for the measurement of the mass flow of solids in pneumatic conveying systems or for volumetric flow measurements. The cross-correlation flowmeter uses a microwave (or gamma ray, ultrasonic, or photometric detectors) as the densitometer and a measurement of the time it takes for particles to travel a known distance to determine velocity. 

Note that in some equations, the values of constants are a function of the system of units used. These constants have dimensions and are known as dimensional constants. For example, many flowmeters measure volumetric flow rates, Qv, by measuring heads of fluids, Ah. Typically, Qv oc a/Ah or Qv = csfKh. Here, as Qv[f y[Ah, c is a dimensional constant. Dimensionally, L3T-1[=] cs/L or c [=] L2 5T 1, and the value of c will depend upon the units of both Qr and Ah. 

Barolo et al. (1998) developed a mathematical model of a pilot-plant MVC column. The model was validated using experimental data on a highly non-ideal mixture (ethanol-water). The pilot plant and some of the operating constraints are described in Table 4.13. The column is equipped with a steam-heated thermosiphon reboiler, and a water-cooled total condenser (with subcooling of the condensate). Electropneumatic valves are installed in the process and steam lines. All flows are measured on a volumetric basis the steam flow measurement is pressure- and temperature-compensated, so that a mass flow measurement is available indirectly. Temperature measurements from several trays along the column are also available. The plant is interfaced to a personal computer, which performs data acquisition and logging, control routine calculation, and direct valve manipulation. 

A typical heat balance for Run LSF 34 on No. 6 oil is given in Table V. The calculated efficiencies are also given in the table. Heat input terms consist of the input heat from the fuel, the fuel sensible heat, and the makeup water sensible heat. The heat available from combustion of the fuel is calculated from the measured volumetric flow rate, the measured fuel heating value, and the measured fuel density at the nozzle temperature. The fuel sensible heat contains the fuel mass flow rate, the measured temperature at the nozzle, a reference temperature, and an estimated specific heat for the oil of 0.480 Btu/lb°F. The specific heat was taken from graphical information in the ASME Power Test Code. Similarly, the water sensible heat calculation contains a tabular value... 

Both gas flow rates and liquid flow rates can be measured by a wide variety of devices such as bellow meters, Venturi nozzles, nutating disk meters, orifice meters, rotameters, weirs (for liquids), Pitot tubes, and magnetic meters among others. Some devices measure volumetric flow directly as with meters in which the space between rotating paddles incorporates small volumetric displacements of fluid. Other device measure the flows indirectly by measuring the pressure drop caused by an orifice between two different sites in the pipe, or the change in voltage of a heated wire. 

Since the pressure in a draining foam with CBF is established more rapidly than in a foam with NBF [12] and the experimentally measured volumetric flow rate exceeds the theoretical at complete tangential immobility of surfaces, it has been assumed [51] that the profiles of border radii obtained are non-equilibrium. 

The mass flow rates of process streams must be known for many process calculations, but it is frequently more convenient to measure volumetric flow rates. A common procedure is therefore to measure V and calculate m from V and the density of the stream fluid. 

Errors due to approximations in the experimental data analysis. Several potential errors were introduced when the measured volumetric flow rates were converted to molar flow rates. Volumetric gas flow rates were converted using the idc il gas equation of state, which is approximate, and the volumetric liquid flow rate was converted using a tabulated density that may not have been measured at the system temperature. Also, the fact that a physical property value has been published is no guarantee that it is correct. 

The measured volumetric flow rate of ethane at 10.0 atm absolute and 35 C is 1.00 x 10 L/h. Using an estimated value of the second virial coefficient in the truncated virial equation (Equation 5.3-4), (a) calculate V (L/mol) (b) estimate the compressibility factor,and (c) determine the mass flow rate of ethane in kg/h. 

The TPR experiments were performed in an Altamira AMIl instrument with a flow of 10 vol.-% H2 in Ar. A heating rate of 3 K / min and approx. 100 mg of sample were chosen to enhance resolution and avoid "hot spots" Prior to the reduction experiments, the samples were activated in a helium flow containing 10 vol.-% O2 up to a maximum temperature of 400 °C at a rate of 5 K / min. The carbon monoxide adsorption isotherms were measured volumetrically at 25 °C in a home-build all-steel apparatus. The samples were dehydrated at 250 °C for 18 h prior to the adsorption measurements, ESR spectra were recorded on a Bruker ESP 300 spectrometer at 77 K. 

A packed column in gas chromatography had an inside diameter of 5.0 mm. The measured volumetric flow rate at the column outlet was 50 mL/min. If the column porosity was 0.45, what was the linear flow velocity in cm/s ... 

Quite a number of technologies are available for measuring volumetric flow rates. These include differential pressure transmitters, vortex meters and magnetic flow meters. Each has its advantages and disadvantages. 

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