Ejector systems Example

Example 6-12 Temperatures at Barometric Condenser on Ejector System... 

Dusts, particle sizes, 225 Dusts, hazard class, 521-523 Explosion characteristics, 524 Efficiency, centrifugal pumps, 200 Ejector control, 380 Ejector systems, 343, 344, 351 Air inleakage, table, 366, 367 Applications, 345 Calculations, 359-366 Chilled water refrigeration, 350 Comparison guide, 357, 375 Evacuation lime, 380, 381 Charts, 382 Example, 381 Features, 345... 

In practice, the vapor that is to be condensed sometimes contains noncondensible gases such as air. The presence of these noncondensible gases can significantly lower the heat transfer rate from that which would exist under the same circumstances with a pure vapor. A common example is the build-up of air in power plant condensers. These condensers usually operate at a substantial vacuum and some air entrainment is unavoidable. The continuous removal of air by specially designed ejector systems is essential to maintain the condenser vacuum and to maintain acceptable condensation rates. In some chemical plants, the separation of constituents is sometimes produced by condensing one gas from a mixture of gases and in such cases the presence of a noncondensible gas is unavoidable. 

As another example of calculation and dimensioning of pneumatic conveying systems we consider an ejector shown in Fig. 14.20. In fluidized bed combus tion systems a part of the ash is circulated with the hot flue gas. The task of the ejector, is to increase the pressure of the circulating gas to compensate the pressure losses of the circulation flow. The motivation for using an ejector, rather than a compressor, is the high temperature of the flue gas. The energy... 

A cross-sectional view of the radiant tube and recuperator combination, shown in Figure 21.8, is an example of the application of preheated air combustion system. A recuperator is installed at the exit section of exhaust gases. An air ejector is used to compensate the pressure drop required for passing the exhaust gases through the recuperator prior to the release of exhaust gases to the atmosphere. 

A wide variety of ejector designs may be used. The choice depends on the shape of the article, its position within the mold and the force retaining it Figure 4-11 shows a pin system as an example of an ejector in an injection molding tool. 

SOFC systems can be designed to include a heat recovery component such as an adsorption chiller heater for CHP applications [72-76]. An example is a small (1-lOkW) methane-fueled residential CHP SOFC system that integrates CGR, AGR, and internal reforming [73]. The system consists of a fuel-cell stack, steam prereformer, various fluid delivery devices (blowers, ejectors, compressor, and water pump), heat exchangers, and catalytic combustor and power conditioning device along with a heat recovery component. Based on certain system parameters (50active area, nominal cell temperature of 800 °G, current density of 0.57 A cm , power density of0.40-0.43 Wcm , S/G ratio of 2.0, SOFC... 

If using a control with an additional ballast load it is normally reasonable to use a bypass from the outlet of the ejector back to the suction side and thus not give an additional external load to the system. For example, when pollutants are in the suction flow and ambient air is sucked in, this air will be saturate with the toxic components and carry them out and pollute the environment. 

The fluid entering at A does not have to be the same as that in pipe C/B/D. The most common use of the ejector is in steam systems, with steam being the fluid passing through the narrow pipe and jet A. So, ejectors are used to pump air, for example, to maintain vacuum in the condensers of steam turbines. They are also used to pump water into boilers, and since the steam mixes with the pumped water it also preheats it. The steam is also used to circulate lower pressure steam in steam heating systems. In this application it is closest to its normal use in fuel cell systems. 

Feed systems can be hybrids, combining dry or gas feed with liquid feed components. Dry and liquid systems usually include a dry-to-liquid conversion (using a dissolving tank) that subsequently combines this liquid with another liquid. Gas-liquid hybrid systems can mix the gas with water first or with another liquid chemical in a reaction chamber. Chlorine dioxide generators using chlorine gas are an example of this type of system. The chlorine dioxide formed in the reaction is ultimately mixed with ejector water, and this solution is then mixed with process water at the point of delivery. 

Fig. 18. Half sectional view to give the general build-up of a compression tool. In this example a multi-cavity semipositive type tool is shown partly open. A—top plate B—core pin C—male die or plunger D—guide pin E—push back rods (to return ejection system) F—guide pin bush G—bottom plate H—risers or parallels J—ejector pin K—ejector or knockout bar L—female die or die cavity M—pressure pads.

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