Collector plate

Bands of ions of different m/z values and separated in time in a broad ion beam traveling from left to right toward the front face of a microchannel assembly. The ions produce showers of electrons, and these are detected at the collector plate, which joins all the elements as one assemblage. 

For a microchannel plate, the back end of each element is left open, as shown in Figures 30.5 or 30.6, and forms a microchannel. Any electrons emerging from any element are all detected by the one collector plate. 

The strength of the ion current relates to the number of ions per second arriving at the collector plate, and a mass spectrum can be regarded as a snapshot of the current taken over a definite period of time. Because of the finite time taken to produce a mass spectrum, it is a record of the abundances of ions (often mistakenly called intensities of ions). 

Figure 11. Liquid collector plate. (Courtesy of Norton Chemical Process Products Corporation.)...

For columns in which there is a substantial flash of the feed liquid, or in which the feed is a vapor of a different composition than the internal vapor, a collector plate can be installed above the feed point. The purpose of this plate is to provide mixing of the vapor phase in the gas risers so that a more uniform vapor composition enters the rectifying section of the column. 

Figure 11 shows a t pical liquid collector plate for a column that uses one side downcomer to withdraw the liquid. The maximum diameter for such a design is about 12 ft, which is limited by the hydraulic gradient necessary for such a liquid flow-path length, For larger diameter columns, two opposite side downcomers or a center downcomer normally is used unless the total amount of liquid collected is relatively small. 

A liquid collector plate must be of gasketed construction so that it can be sealed to the sup-... 

The gas risers must have a sufficient flow area to avoid a high gas-phase pressure drop. In addition, these gas risers must be uniformly positioned to maintain proper gas distribution. The gas risers should be equipped w ith covers to deflect the liquid raining onto this collector plate and prevent it from entering the gas risers where the high gas velocity could cause entrainment. These gas riser covers must be kept a sufficient distance below the next packed bed to allow the gas phase to come to a uniform flow rate per square foot of column cross-sectional area before entering the next bed. 

Very small particles can be collected but large ones (above 5 pm) can cause arcing across the narrow gap between collector plates. A coarse filter should first remove these large particles. Precipitators are not normally suitable for wet environments since excessive moisture can cause electrical tracking and failure. Resistance to airflow is negligible. 

Figure 2. Total ionization source of Rapp et al59 where F is the filament electron lenses are labeled 1, 2 and 3 guard plates G ion collector C1 and field plate C2 electron collector shield S electron collector cylinder T and electron collector plate P.

Three properties of the current collector plate are particularly important for CFCD models. One is electric conductivity, the second is thermal conductivity, and the third is surface wettability. These properties for materials such as graphite and metals are well documented in standard textbooks. 

To measure the current distribution in a hydrogen PEFC, Brown et al. ° and Cleghorn et al. ° employed the printed circuit board approach using a segmented current collector, anode catalyst, and anode GDL. This approach was further refined by Bender et al. ° to improve ease of use and quality of information measured. Weiser et al. ° developed a technique utilizing a magnetic loop array embedded in the current collector plate and showed that cell compression can drastically affect the local current density. Stumper et al."° demonstrated three methods for the determination of current density distribution of a hydrogen PEFC. First, the partial membrane elec-... 

Localized AC impedance and current distributions were measured by Brett et al." on a single linear channel with the segmented cathode current collector plate. Figure 26 shows their measured current density and membrane resistance distributions along the... 

An example of a study in which this approach was applied involved the use of a transmission electron microscopy (TEM) grid as the collector plate in the electrostatic precipitator (Witkowski et a ., 1988). After sample collection, analysis by TEM (vide infra) could then be carried out. 

Figure 16.6—Linear time of flight (TOF) and principle of the reflectron. 1) Sample and sample holder 2) MALDI ionisation device 3 and 3 ) extraction and acceleration grid (5 000 V potential drop) 4) control grid 5) multichannel collector plate 6) electron multiplier 7) signal output. The bottom figure shows a reflectron, which is essentially an electrostatic mirror that is used to time-focus ions of the same mass, but which have different initial energies. This device increases resolution, which can attain several thousand.

The membrane tubes must be sealed, possibly to each other and to the collector plate of the reactor vessel. The sealing has to be adherent and mechanically strong but also gas-tight and thermally resistant, up to temperatures of at least 700°C. These high demands make sealing one of the most important problems in current high temperature membrane technology. 

Heat transfer by natural convection across an enclosed space, called an enclosure or, sometimes, a cavity, occurs in many real situations, see [34] to [67]. For example, the heat transfet between the panes of glass in a double pane window, the heat transfer between the collector plate and the glass cover in a solar collector and in many electronic and electrical systems basically involves natural convective flow across an enclosure. 

Separate the unbound fraction by short low speed centrifugation (15 min/10000 g). Alternatively a vacuum filtration with collector plate can be applied. 

Current collector — In the battery discipline, a good electron conductor support designed to transfer electrons from the external circuit to the active materials of the cell. Current collectors are usually metal foils or nets that are inert under the operational chemical and electrochemical conditions. In some cases carbon cloth is also used. In secondary - lead-acid batteries the chemical nature of the current collectors (plates, grids) is particularly imperative, as it influences the self-discharge and the performance under overcharge and discharge conditions. Frequently, current collectors have also the important role of imparting mechanical stability to the electrodes. 

Under suitable conditions, the recoiled reaction products can be collected on a collector plate during the Irradiation. 

Fig. 4.4. Wire and plate dry electrostatic precipitator, reprinted from Oglesby and Nichols (1978), p 269 by courtesy of Taylor and Francis Group, LLC. The parallel collector plates and bottom dust bins are notable. In this case, wires are hung between the plates - weights for keeping them vertical are just visible. Structural and operating data for a recent precipitator are ...

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