For calculation the area of the critical section (throat), the condition ofequality of the flow rate in the throat to the sound velocity is used.81Fig. High-pressure gasinternal energy flows III and IV, converted into motive kinetic energy in expansion in the converging and divergingdiffuser sections, are calculated. Figure 2 shows a diagram of the calculated model of the ejection process based on theHYSYS simulation system with material I, II and energy III-VII flows.Expansion of high-pressure (ejecting) gas I in the nozzle is simulated by two successive expanders 1and 2 for calculating the flow parameters in the converging and diverging diffuser sections. Their elementary units are expanders, compressors, mixers, etc., that simulate expansion,compression, and mixing processes and combined with specially developed commercial functions andsubroutines, they allow creating a model of relatively complicated processes, including the ejection process.A diagram of the experimental ejector model consisting of nozzle, mixing chamber, and diverging partis shown in Fig. These systems can be used to simulate notonly the elementary but also the complex processes that take place with a change in the phase state or chemicaltransformations.
#Gas ejector design calculation pro
However, serious problems arise in using the calculation equations in these studies for designingindustrial ejector systems.One of the most serious problems is the necessity of calculating the function of state of complexmixtures of real gases in the wide ranges of pressure and temperature variations that take place in industrialejectors.Simulation systems such as HYSYS and PRO II, widely used in designing oil refining processes andhaving a broad base of thermodynamic properties both for individual substances and for hypothetical componentsof continuous crude oil mixtures, can be used to solve this problem. Not only the theoretical principles of the process at subsonic and supersonicflows but also selection of ejector design parameters for implementation of so-called calculation operatingregimes characterized by the appearance of critical sections in different parts of the ejector are examined inthese studies. In addition,it is frequently necessary to calculate ejectors that operate with vapor and gas streams with an extremely widerange of thermophysical properties: from hydrogen to heavy crude distillate vapors.Vapor and gas ejection processes with consideration of the real thermophysical properties have beencalculated in many studies. This frequently leads to an unsubstantiated increasein the cost of the process or selection of ejector design dimensions which are far from optimum. For this reason, it is not possible to assess the legitimacyof using it for systems with thermophysical properties different from the vaporair mixtures for which it isrecommended.These methods recommend increasing the calculated flow rate of a high-pressure gas by some constantin designing ejectors for evacuating and compressing gases. However, there are no references as to how this dependence wasconstructed in the descriptions of these methods. 62 64,January February, 2004.0009-3000802004Plenum Publishing CorporationIn practice, methods based on use of nomograms that correlate the ejection factor with the degree ofexpansion of the ejecting gas and degree of compression of the ejected gas are used in designing ejectors foroil refineries and petrochemical plants.
Transl at ed from Khi mi ya i Tekhnol ogi ya Topl i v i Masel, No.
80Chemistry and Technology of Fuels and Oils, Vol.