Injection geometry

Another type of reactor using a simple injector is a reactor with a dome type cover.In this case, the injector is installed on the bottom plate of the reactor. Figure 11 shows the typical configuration of this type of reactor. In this case the dome is usually heated to a proper temperature by a separate heater to prevent precursor condensation on it. It is rather difficult to expect uniform deposition of a thin film from this asymmetrical gas injection geometry. However, it has actually been proved that good thickness and compositional uniformity are obtained over the 8 wafer surface for Ta O thin films. Figure 12 shows the typical variation in thickness of a Ta O thin film using this reactor. 

From Equation 8, it can be derived that the vaporization efficiency increases with an extension of the total surface area and with the time of contact between steam bubble and oil. In practice, the vaporization efficiency can be influenced by the depth of the oil layer and the steam injection geometry. The shallower the oil layer, the higher the risk that the steam leaves the oil surface without being saturated. At the other extreme, for deep oil layers, the contact time is longer but then problems can occur with the agitation, leading to an insufficient renewal of the upper oil layer and a nonuniformly treated oil mass. 

AIGalnP LEDs, (b) Current crowding in a mesa-structured GaN-based LED grown on an insulating substrate, (c) Lateral injection geometry. The corresponding equivalent circuits are shown as well. 

Although the results indicate a good ionization stability, the problem of the unwanted formation of relatively large droplets could not be completely solved. This is likely due to the injection geometry since liquid is injected from one side, a liquid film occurs at one side of the nebulization channel. Further optimization of the injection geometry, such that the liquid is enclosed by the nebulization gas at both sides, might reduce this unwanted effect. 

Several research groups implemented carbohydrate analysis on-chip with direct detection of underivatized sugar molecules. Electrochemical detection is the most attractive approach, as it offers reasonable sensitivity and selectivity, and it is ideally suited for microchip format. Schwarz et al. [203] developed amperometric detection of sugars using microfabricated copper electrode. They separated fructose, sucrose, and galactose in 70 s on a glass chip with 50-p,m wide and 20-p,m deep microchannel and double tee injection geometry. The detection was based on Teflon-coated platinum wire plated with copper and inserted in the end of the separation channel etched in a conical shape. The detection limit down to 1 JtM was achieved. Hebert and coworkers [204] reported an... 

Design Evolution 4 have developed a sequential multiport resin injection system (SMRIM) that allows controlled resin injection geometry using sequential filling of multiple ports, permitting the resin flow to be changed at any one of the ports. 

In contrast to a direct injection of dc or ac currents in the sample to be tested, the induction of eddy currents by an external excitation coil generates a locally limited current distribution. Since no electrical connection to the sample is required, eddy current NDE is easier to use from a practical point of view, however, the choice of the optimum measurement parameters, like e.g. the excitation frequency, is more critical. Furthermore, the calculation of the current flow in the sample from the measured field distribution tends to be more difficult than in case of a direct current injection. A homogenous field distribution produced by e.g. direct current injection or a sheet inducer [1] allows one to estimate more easily the defect geometry. However, for the detection of technically relevant cracks, these methods do not seem to be easily applicable and sensitive enough, especially in the case of deep lying and small cracks. 

For this kind of case, a modification of the dilution method is being developed. Instead of using an external fixed-geometry measurement chamber, a suitable part of the process, e.g. a stretch of pipe, is used. A radiation detector is mounted on the outside of the pipe, and a tracer emitting sufficiently hard gamma radiation is used. As sufficient mixing can be achieved by injecting upstream the separator the radiation level found will be strictly proportional to the concentration and thus inversely proportional to the true flow rate. 

Fig. 18. Jet trajectory of a round jet in bounded cross flow where J = Pj V j p (a) flow geometry, ratio of height of tunnel to diameter of injection tube HID) = 12 and (b) flow streamlines where the data points are experimental deterrninations and the lines correspond to calculated predictions for (—)...

Validation and Application. VaUdated CFD examples are emerging (30) as are examples of limitations and misappHcations (31). ReaUsm depends on the adequacy of the physical and chemical representations, the scale of resolution for the appHcation, numerical accuracy of the solution algorithms, and skills appHed in execution. Data are available on performance characteristics of industrial furnaces and gas turbines systems operating with turbulent diffusion flames have been studied for simple two-dimensional geometries and selected conditions (32). Turbulent diffusion flames are produced when fuel and air are injected separately into the reactor. Second-order and infinitely fast reactions coupled with mixing have been analyzed with the k—Z model to describe the macromixing process. 

The flow process in an injection mould is complicated by the fact that the mould cavity walls are below the freezing point of the polymer melt. In these circumstances the technologist is generally more concerned with the ability to fill the cavity rather than with the magnitude of the melt viscosity. In one analysis made of the injection moulding situation, Barrie showed that it was possible to calculate a mouldability index (p.) for a melt which was a function of the flow parameters K and the thermal diffusivity and the relevant processing temperatures (melt temperature and mould temperature) but which was independent of the geometry of the cavity and the flow pattern within the cavity. 

In addition, due to the likely variation between injections and the convoluted geometry of the internal parts of the valve, a useful theoretical treatment of the valve dispersion would be very difficult if not impossible to develop. 

To determine the appropriate injection rate, a field test should first be performed at one of the industry-sponsored full-scale loop test facilities. The optimum mixture, its injection rate, and location of injcciioii points will be a function of flow geometry, fluid properties, pressure leinpcrature relationships, etc., that will be encountered in the actual field application. The appropriate injection rate and location of injection jii iiiis can be determined from this test by observing pressure increases, which indicate that hydrate plugs are forming. 

The polymers studied and the experimental procedure were described in the last section. The samples were made of the same PC-TLCP composite and the pure TLCP Vectra A950, respectively. To study the influence of sample forms and geometries on mechanical constants, plate samples (80 x 80 x 2 mm-) were also injection molded with a film gate. Tensile samples were then cut from the plate in the longitudinal (//) and transverse... 

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