Study On Characteristics Of The Ejector In Quasi Two-Stage Compression Heat Pump Coupled With Ejector

Comparing with the conventional air-source heat pump system, the quasi two-stage compression heat pump system with economizer can effectively improve the deficiencies of conventional air-source heat pump when running in low ambient temperature, it has becoming an effective technology guarantee to enlarge the application of air-source heat pump in cold regions. On the base of the quasi two-stage compression heat pump system with economizer, considering that it can make use of the pressure energy of liquid with high pressure and minish energy losing of the system, ejector is adopted to replace the throttle in the assistant loop, and design the quasi two-stage compression heat pump system coupled with ejector. The method is adopted that combining theory analysis and experiment to study this heat pump system coupled with ejector in detailed.In the paper, interrelated background and working principle of the quasi two-stage compression heat pump system coupled with ejector and the ejector used in the system are introduced in detail firstly. Working process of ejector used in the system are analysed mainly. As core parts of quasi two-stage compression heat pump system coupled with ejector, the ejector was studied theoretically with an accurate of the ejector configuration Parameters to instruct the designing of the ejector and to prove the system's working performance. The ejector model was developed based on aerodynamics function and classical thermodynamics. Flowing characteristics of flow in the nozzle of ejector and working characteristics of ejector is discussed in detail.Secondly, the principle of quasi two-stage compression heat pump system coupled with ejector is introduced. The quasi two-stage compression process is analyzed in thermodynamics, and the compression work is deduced. The system coupled with ejector is analyzed in thermodynamics in detail, and the calculated method of enthalpy of each state is presented. Integration with the analysis model of the ejector used in the system, characteristics of quasi two-stage compression heat pump system coupled with ejector is discussed in detail, including the variations of the performance of the heat pump system with the equivalent diameter of nozzle throat,proportion of acreages between imports and exports in convergent section of mixing chamber and acreage of mixing chamber. The characteristics of ejector under the various operation conditions and the optimized design criteria of the ejector were presented according to the above analysis.At last, based on the theoretical analyses,the structure of the ejector used in the quasi two-stage compression heat pump system coupled with ejector is designed, experiment project is designed and performances of prototype are tested to verify theory analysis. At the same time, experiment data of the prototype are compared with those of the conventional system and the conventional quasi two-stage compression system to test the correctness of the theory. On the one hand, the test results show that the quasi two-stage compression heat pump system coupled with ejector can enlarge the applying area of air-source heat pump, the heating capacity and heating EER of this system coupled with ejector is increased remarkably. On the other hand, the test results proved that the theoretical analyses about flowing characteristics of flow in the ejector and characteristics of quasi two-stage compression heat pump system coupled with ejector are validity and appropriateness.