The Analyses And Study Of Numerical Simulation On Steam Ejector

In conventional evaporation process, the energy of secondary steam is often wasted, butthe heat pump evaporator system can effectively solve this problem. The core component ofthis system is the steam ejector, which has some advantages，such as low cost, reliableoperation, and simple structure. However, the internal flow process is quite complicated, sothe steam ejector needs to be deeply research.In order to describe the working process of the steam ejector better, as well as achievemore energy-saving effect in applications, This paper applied STAR-CCM+software toanalyze the3D flow field of a typical single-nozzle steam ejector. An explicit finite volumescheme was applied to solve the axisymmetric Navier-Stokes equations with a standardk-epsilon turbulence model, and the method of wall functions was used near wall. Theeffects of the motive steam pressure, suction steam pressure, and the position of nozzle, thenozzle throat diameter on the operating state, and flow field state were analyzed. A new typeof three-nozzles steam ejector was designed and simulated to investigated and analyzed itsworking capacity., which shows that three-nozzles steam ejector have some advantages.The simulation results indicate that operating conditions and structural parameters havegreat influences on the performance of the steam ejector. The internal flow field status ofsingle nozzle and three nozzle steam ejector can be analyzed by simulation. The velocity andpressure nephograms were used to explain the mixing process occurring inside the ejector.The optimum operation parameters, suitable nozzle position, and throat diameter of thesingle nozzle steam ejector were obtained, and the entrainment ratio of the steam ejectorachieve maximum, it should have clear effect on energy-saving. Compared with the classicsingle nozzle steam ejector, the three-nozzles steam ejector could work more stably when theworking steam fluctuates; therefore it is more suitable for the actual steam ejector systemwith volatile working conditions. The working and entrainment steam in the three-nozzlesteam ejector mix uniformly more rapidly than those in the conventional single-nozzle steamejector, so that the length of its mixing chamber can be shortened, thus both themanufacturing materials and installing space can be saved. Different throat diameters of thethree-nozzle steam ejector were compared, and studies show that law of “equal area” issuitable for design of a multi-nozzle steam ejector. The effect of number of nozzles on the multi-nozzle steam ejector’s performance were investigated, the optimum number of thenozzles is four for the steam ejector, and the excessive number of nozzles will cause morefriction, which will lead to the decreases of the work efficiency.