Ejector systems Calculations

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... 

Calculating the Pressure Loss of an Ejector in a Pneumatic Conveying System 1353... 

Reprinted from M. Lampinen, Calculation Methods for Determining the Pressure Loss of Two-Phase Pipe Flow and Ejectors in Pneumatic Conveying Systems, Acta Polytechnica Scandinavica, Mechanical Engineering Series No. 99, published by the Finnish Academy of Technology, Helsinki, 1991. 

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... 

TABLE 14.3. Calculations for an Ejector of a Pneumatic Conveying System, According to Fig. 14.20... 

Other pieces may have to be elevated to enable the system to operate. A steam jet ejector with an intercondenser that is used to produce a vacuum must be located above a 34 ft (10 m) barometric leg. Condensate receivers and holding tanks frequently must be located high enough to provide an adequate net positive suction head (NPSH) for the pump below. For many pumps an NPSH of at least 14 ft (4.2 m) H2O is desirable. Others can operate when the NPSH is only 6 ft (2 m) H2O. See Chapter 8 for a method of calculating NPSH. 

Ejector. Gas chamber pressure needs to be known in order to calculate ejector power input. A semiempirical equation was developed by Henzler (10) that related the entrainment ratio to other system variables ... 

Detailed design and technoeconomic calculations in close association with manufacturers of compressors, steam jet ejectors, and steam dryers and with utility companies are required to make confident conclusions regarding the optimal steam reuse and recycle systems for steam dryers. 

The above optimization problem is applicable to systems involving air and water only. It ignores vapour superheat at the ejector inlet, vapour sub-cooling and liquid sub-cooling in condenser area calculations, and also assumes a simple log-mean temperature driving force (LMTD) without any correction factor. Hence, condenser area calculations are approximate but sufficient for optimization. Actual condenser design is quite complex for systems... 

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