The Optimization Analysis Of Ejector Performance

The steam ejector with natural water as refrigerant, can use low grade energy inrefrigeration such as solar energy, industrial waste heat, exhaust steam etc. and thiseffectively improve the energy efficiency. More and more research of steam ejector asbooster parts used in refrigeration system are done. Due to rapid expansion, which involvesnot only problems such as heat transfer, mass transfer, but also problems such as shockwave and the interaction between shock wave and boundary layer, which makes the flowprocess complex, is easily happened in steam transonic flow. The mixing mechanismbetween the main steam and the second steam is still unclear, and the way of halfexperience and half theory is still adopted to design the ejector. The EES in which thephysical parameters of water steam can be calculated and the classic design theory ofejector are used to forecast the ejector geometry size in this paper. The influence ofoperating conditions and geometry parameters on the performance of the ejector isnumerical simulated by employing the FLUENT, and the structure size of ejector is furtheroptimized.The isobaric mixed theory is choosen as the basis modle in this paper, and the steamtheoretic flow at the internal of the ejector is analyzd in thermodynamically; The designtheory of ejector and the EES which is used to call the physical parameters of the steam iscombined to write the procedure for forecast the ejector geometry size;The experimentaldatas and the simulation results are compared to analyze the feasibility of the procedure, theerror between them is within 10%; According to the air conditioning condition, the ejectorthat conform to the loading condition is designed, and the influence of ejector performanceby changing the parameters of main steam, second steam and condenser backpressure ofejector is been studied, in addition, the draw ratio of the uniform mixing chamber(L/D) andthe diameter ratio of the ejector exit and taper mixing chamber(d/D) is also been reserched.The simulation shows that the entrainment ratio of ejector is in direct proportion to thetemperature of second steam, while the main steam temperature is not the higher the better,the main steam temperature’s peaked appers at 130 ℃, the condenser back pressure inejector exit is increased with the rise of the evaporation temperature and main steamtemperature. The influence of geometric size on ejector’s performance can not be ignored,there is optimum value of draw ratio(L/D) of the uniform mixing chamber and the diameterratio(d/D) of the ejector exit and taper mixing chamber when the operating condition isconstant. The optimum value of draw ratio(L/D) of the uniform mixing chamber is 5 andthe diameter ratio(d/D) of the ejector exit and taper mixing chamber is 4.