Flow measurements total

Capacity. Pumps deHver a certain capacity, Q, sometimes referred to as flow, which can be measured directly by venturi, orifice plate (11), or magnetic meters (12) (see Flow measurement). The indirect way to determine capacity is often used. Whereas this method is less accurate than applying a flow meter, it often is the only method available in the field. The total head is measured and the capacity found from the pump head—capacity (H— curve (Fig. 2). More recently, sonic flow meters (13) have been used, which can be installed on the piping without the need for pipe disassembly. These meters are simple to use, but require relatively clean single-phase Hquid for reHable measurements. 

Flow measurements using nonintrusive or low mechanical ac tion principles are desired, such as magnetic, vortex-shedding, or Coriolis-type flowmeters. Orifice plates are easy to use and reliable but have a limited range and may not be suitable for streams which are not totally clean. Rotameters with glass tubes should not be used. 

The air volume flow rate plays a major role in planning, commissioning, and running industrial ventilation systems, in the planning phase of a system, the supply, exhaust flows, and total flow rates are specified. When the system is built and running, the contractor and/or the client measures the airflows to determine if they agree with the specification. In such a situation, it is of interest to... 

Unmeasured temperatures or concentrations that correspond to enthalpy or component flows in Vd are determinable if the total flow rate of the stream is measured. Otherwise, they are indeterminable. Measured total flow rates are nonredundant and unmeasured total flow rates are indeterminable. The analysis of intensive constraints between variables may change previous classification. 

It is important to remember that in these equations Q is the measured total flow rate and u is calculated from Q. 

After 2 h of ozone exposure, there was a significant change (p < 0.05) in Fvc, KMF, and airway resistance (Raw) Several other measures (feVi, Vjq, and V35) were lower after 2 h of exposure, but the statistical significance was borderline. However, after 4 h of exposure, all flow measures were significantly decreased, compared with controls. After 4 h, increased, FVC decreased further, and feV decreased significantly. Residual volume, functional residual capacity, and total lung volume did not change as a result of the ozone exposure. 

It should be noted that the frictional drop was calculated by subtracting the hydrostatic head and acceleration losses from the measured total pressure-drop where void data were lacking, a homogeneous flow model was assumed. This modification of X by use of the Froude number appears very similar to the technique used by Kosterin (K2, K3) for horizontal pipes, in which the equivalent of volume-fraction of gas flowing, with mixture Froude number as the correlating parameter. 

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. 

C. Flow Measurement by Pressure Drop across an Orifice. Another common scheme for the measurement of flow is based on the determination of the pressure drop on either side of a constriction, such as an orifice or venturi. Either a liquid-filled differential manometer or a pressure transducer with associated digital readout may be used for this pressure measurement. The flow rates determined by these meters are in units such as cm3/s, and it is necessary to make a correction for total pressure to convert these to standard cm3/s or mol/s. 

Total error of an orifice-type flow measurement, using a 2% full-scale d/p cell, as a function of actual flow. 

Other, less accurate methods (1-3% FS) of solids flow measurement include the impulse and the accelerator flowmeters. In the loss-in-weight-type measurement, the total weight of the supply tank is measured and that signal is differentiated by time. The rate at which the total weight is dropping is the mass flow from the tank. These systems do not provide high precision (1% AF over a 10 1 range), but are suited for the measurement of hard-to-handle process flows because they do not need physical contact with the process stream. 

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. 

This is a test to assess the degree of airway limitation. It is easy to perform and relatively inexpensive. The patient takes a full inspiration to total lung capacity and then blows out forcefully into the peak flow meter. The best of three recordings are normally taken. The peak flow measures the expiratory flow rate in the first 2 ms of expiration and can overestimate the extent of lung function in patients with moderate to severe airway limitation. Other tests such as... 

Radial distributions of gas-phase characteristics were measured from the wall to the center of the column in 1/4-inch increments. For gas-liquid flows, steady-state operation was achieved in 10 minutes, whereas for gas-liquid-solid flows, measurements were not performed until one hour after flow conditions were established. At the end of each run, average gas holdup was measured by quick closure of the feed stream valve. The sampling rate for the conductivity probes was 0.5 millisecond per point, and the total sample time for each local measurement was 60 seconds. These sampling conditions are comparable to those of another investigator of gas-phase characteristics in bubble columns (11). 

In a typical analysis the columns are cooled to about —75° C. by dry air precooled by liquid N2. Then the gas sample is injected into one column by a Perkin-Elmer sampling valve the second column is for reference. After sampling is complete, the liquid N2 is removed, and the air flow is continued for about 5 minutes or long enough to warm the columns to about —10° C. and remove the 03. Yields, as percent of current, are calculated from the gas chromatographic, amperage, sample volume, and total gas flow measurements. 

Hence, in order to measure the friction of flowing poljnners with slip in axisymmetrical capillaries, it is simply a question of measuring total and entrance pressure losses. The curves obtained in this way and relations (4a) and (5a) can then be used to determine the values of Kec, Ktc, nec and ntc- It is then possible to deduce the values of Kc and n by appl3dng relations (6) and (7). In addition, these same curves and relations (4b) and (5b) can be used to determine the values of Ked, Ktd, ned and ntd-... 

Table B.4 represents a composite mass balance for the entire pilot-plant operation. Any differences in the totals are directly attributable to sampling error, experimental error in conducting the Dean-Stark analysis, and the flow measurement error.

Conventional DSC measures a sample s total heat flow. This total heat flow is comprised of a heat capacity component and a kinetic component [Eq. (5)]... 

Fig. 2 shows a horizontal cross-section through NGFs coupled shear flow test (CSFT) cell. This biaxial cell allows fractured samples (14 x 12 x 5 cm) to be displaced by a maximum 8 mm under controlled fracture normal stresses and temperatures up to 80°C. Variation in fracture aperture (dilation) is measured by a total of four displacement gages, whereas shear displacement is measured by a total of two gages. The flow measurements, as illustrated in Fig. 2, measure the total flow in the direction of the fracture plane and do not differentiate between fracture and matrix flow. To quantify the matrix flow component, tests on non-fractured samples with the same principal geometry as the fractured tests and under the same stress conditions, were conducted in the CSFT cell. 

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