Design Of Jet Vacuum System Based On Gas Dynamics And Thermodynamics Optimization Analysis

Jet vacuum pump is applied broadly in petrochemical,metallurgy,refrigeration and food industry due to its simplicity and reliability as well as it has no motive part and no costs of mechanical work and electronic energy.The purpose of this article is to conclude the calculation program of ejector’s structure and performance based on the structure design and characteristic curves of ejector which is core unit of jet vacuum pump system.Otherwise,it evaluates the performance and analysis exergy ofjet vacuum system.This paper simulated pressure from PO to P in a closed chamber and the influence of working steam parameters and outlet fluid parameters to extraction time. The results indicated that working steam parameters and outlet fluid parameters has no effect on extraction time before pressure reaches certain value,however,the performance of vacuum system is reduced significantly after this value,and the pressure drop very slow in a closed chamber.It can be seen that the jet vacuum system has the best performance when working steam pressure was 0.78MPa and outlet fluid pressure was 0.095MPa.For the fixed structure of single-stage ejector vacuum system,it concluded that the limiting vacuum increased when the motive steam pressure rise while decreased with outlet fluid pressure.With the increasing of motive steam pressure,the unit swept volume was greater,and the extraction ability of vacuum system increased. At the same time,it is concluded that the greater of outlet pressure,the greater of unit steam consumption,and the energy efficient is poorer.However,the system energy efficient is better with the increasing of suction fluid pressure when the system at stable operation.According to the research,exergy loss in mixing chamber is the main exergy loss compared with working steam pressure and suction steam pressure.The exergy loss of mixing chamber increased from 52.3% to 74.7% with working steam pressure increasing from 0.28MPa to 1.08MPa.However,the exergy loss of mixing chamber decreased from 73.7% to 57.5% with suction steam pressure increasing from 0.02MPa to 0.07MPa.When diameter of mixing chamber increased,both the exergy loss of mixing chamber and the exergy loss of ejector increased.lt has big difference on exergy loss of mixing chamber because the change of diameter of vacuum mixing chamber.According to victoria isentropic ideal ejector model, we can calculate the ideal entrainment ratio under corresponding operating conditions, quantitatively described that the designed ejector of this paper meet ejector efficiency η is greater than the ratio of actual entrainmentratio and ideal entrainmentratio.