Flow rate measurements

An eluted solute was originally identified from its corrected retention volume which was calculated from its corrected retention time. It follows that the accuracy of the measurement depended on the measurement and constancy of the mobile phase flow rate. To eliminate the errors involved in flow rate measurement, particularly for mobile phases that were compressible, the capacity ratio of a solute (k ) was introduced. The capacity ratio of a solute is defined as the ratio of its distribution coefficient to the phase ratio (a) of the column, where... 

Flow rate Measure of the amount of fluid passing through the filter. This is always a variable of filter area, porosity, contamination and differential pressure. 

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. 

The above experimenters have used the technique described to obtain flow rate measurements of the liquid wall-film at various mass velocities, tube dimensions, etc., and some typical results from Staniforth and Stevens (S7) are shown in Fig. 7. Also shown are the values of burn-out heat flux obtained at the four different mass velocities indicated. It can be seen that the liquid-film flow rate decreases steadily with increasing heat flux until at burn-out the flow rate becomes zero or very close to zero. We thus have confirmation of a burn-out mechanism in the annular flow regime which postulates a liquid film on the heated wall diminishing under the combined effects of evaporation, entrainment, and deposition until at burn-out, the film has become so thin that it breaks up into rivulets which cause dry spots and consequent overheating. 

The uncertainty of calculating the Poiseuille number from the measurements must be taken into account. The viscosity-pressure relationship of certain liquids (e.g., isopropanol, carbon tetrachloride) must be kept in mind to obtain the revised theoretical flow rate. The effect of evaporation from the collection dish during the mass flow rate measurement must be taken into consideration. The effect of evaporation of collected water into the room air may not be negligible, and due to the extremely low mass flow rates through the micro-channel this effect can become significant. 

The simulated FBAC consists of an acrylic main reactor (0.5m-H x 0.5m-W x l.Om-L), an air distributor system, particles feeding system including a feed hopper, a discharging sampler, a bag filter for capture of the elutriated fine particles and, pressure and flow rate measurement systems (Fig. 1). The air distributor system has ten air headers. An individual air header is connected with 5 air nozzles and can regulate the airflow rate. The opening ratio of the distributor is 2.1% and each nozzle has four holes for uniform air supply. To measure the pressure fluctuation at an individual air header, high frequency pressure transmitters were mounted at the approach and the exit headers of the FBAC. 

During an analytical cleanup run, the flow-rate must be 5.0 mL min. To check the flow-rate, measure the volume of the eluate in a graduated cylinder. 

For flow rate measurements the volume or, more conveniently, the mass flow is suitable. In the first case a pressure- and temperature-dependent calibration is necessary if the gas does not show ideal behavior. This also applies for heat conductivity as the measured quantity often used in flow meters. Currently, real pressure- and temperature-independent measurement of a hydrogen mass flow of a hydrogenation remains problematic on the laboratory scale, at least for low substrate concentrations. 

Calculate tw from the pressure drop measurements using equation 2.3 and the corresponding values of the flow characteristic (8u/d, = AQhnj) from the flow rate measurements. 

Shaffer (S5) also made some exploratory evaluations of the electrostatic atomization of dibutyl phthalate using a camel s hair brush for the atomizing nozzle. On a count basis 73% of the particles were smaller than 10 microns and the largest particle obtained was 40 microns. The energy input corresponded to 0.5 cal/g liquid atomized (0.00026 kWh/lb) and the charge level on the particles as atomized corresponded to a value of Sps of the order of 3-5 V/micron. Current and flow rate measurements reported by Vonnegut and Neubauer (V4) would correspond to an energy input of 0.1 kWh/lb. 

These investigations showed that the T04 olfactometer can deliver repeatable dilutions, but that an absolute calibration was needed before use. The main problems arise from the flow rates measured in the lower ranges of the rotameter scales, which are less accurate than the upper ranges. If the upper ranges only are used, then consistent results should be obtainable. The olfactometer should be used in the same orientation as when calibrated. 

The signals from flow rate measurements are usually noisy (fluctuate around the actual value) because of the turbulent flow. These signals often need to be filtered to smooth out the signal sent to the controller. 

For each thickness, at least 10 different flow rate measurements were obtained in order to cover the range of flow rates that a DL experiences during normal fuel cell operation. To obfain fhe corresponding permeabilify, fhe pressure drop resulfs were ploffed as a function of the mass flow rate. After this, the Forchheimer equation was fitted to the plotted data to determine the viscous and inertial permeabilities. As expected, the in-plane permeabilities of each sample DL maferial decreased when the compression pressure was increased. It is also important to mention that these tests were performed in two perpendicular directions for each sample in order to determine whether any anisotropy existed due to fiber orienfation. 

Determination of the ratio of solvent to raffinate flow rate Measurement of the separation time (e.g., in a shaking vessel) to evaluate the coaleseenee behavior... 

An improved electrochemical cell for in situ studies is presented in Figure 14.2. In this method a platinized Pt electrode located in the anode compartment serves as the reference electrode. This cell can be installed in a test station. Such a station can have facilities for temperature and pressure control, humidification of reactant gases (e.g., hydrogen and oxygen), gas flow rate measurement, and measurement of half- and... 

Figure 2.8 Dependence of ion intensity of 38 Ba+ and 48Ti+ on nebulizer gas flow rate measured at an rf power of 1300W by ICP-QMS Elan 6000. (S. F. Boulyga, H. j. Dietze and I. S. Becker, j. Anal. At. Spectrom. 16, 598 (2001). Reproduced by permission of the Royal Society of Chemistry.)...

The injector and the detector have dead volumes that affect the total retention volume. In gas phase chromatography, because the mobile phase is compressible, the flow rate measured at the end of the column has to be corrected by the compressibility factor J, which accounts for increased pressure at the head of the column (c.f. 2.2). 

Figures 5.2-10 and 5.2-11 show some results obtained by Hasseni et al. [18] and by Wammes et al. [27] with water, 3 mm glass beads, and nitrogen at different pressures compared with the predictions of the model of Dankworth et al. At moderate pressure (20 bar) the model agrees fairly well with measurements made by both teams. At higher pressures, Dankworth s model overestimates slightly the gas mass flow-rate at the trickling/pulsing boundary measured by our team. On the other hand, it underestimates grossly the gas flow-rate measured by Wammes et al. for the same transition. The reason for this difference is not easily to explain. We suspect that it is a matter of definition of the experimental transition from trickle to pulse flow [28],...

Supercritical carbon dioxide is depressurized through the expansion valves into separator columns 4 and 5, where the product and the unreacted substrates are recovered. The substrates are collected in column 5 and recycled (added to the feed through the pipe connecting column 5 with the feed vessel). The gas phase is finally vented into the atmosphere after flow-rate measurement through a rotameter. The gas can be condensed and recycled on a pilot- or industrial scale. 

Molecular Weight. The molecular weight of polypropylene is typically determined by viscosity measurements. The melt viscosity, or melt flow rate, measured under standard conditions, can also be correlated... 

The mass flow streams at tray j are shown in Figure 6.1 for a countercurrent process of a dilute system. Here the total molar flow rate of the rising gas is constant at V moles/min while the total molar flow rate of the sinking liquid is constant at L moles/min. Both L and V are molar flow rates as long as Xj and Yj are molar fractions. If, however, Xj and Yj describe concentrations, measured in mo/e/m3, then L and V are volumetric flow rates measured in m3/min. 

Scheme of the wall-jet electrode as constructed in our laboratory with (1) solution tank, (2) vessel to control the solution flow rate, (3) pump, (4) flow-rate measuring device, (5) capillary, (6) measuring chamber, (7) counter electrode, (8) reference electrode, (9) working electrode, (10) overflow system to return solution to the solution tank. 

On the basis of melt flow rate measurements after 1, 3 and 5 extrusions, compounds 1, 2 and 2 when used alone at 0.1 in the polypropylene base resin provide superior stabilization to BHT, 7 and 8. Under these conditions compound J2 provides the lowest Yellowness Index (Y.I.) color over other compounds evaluated. 

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