Experimental Study And Optimized Design On The Quasi Two-Stage Compression Heat Pump System Coupled With Ejector

Comparing with the conventional air-source heat pump system, the quasi two-stage compression heat pump system can increase the heating capacity, EER and operation reliability, it has becoming an effective technology guarantee to enlarge the application of air-source heat pump in cold regions. As the ejector has some advantages such as simple structure, low cost, no moving parts, fitting for two-phase working flow fluid and so on, it can be used to replace the throttling valve to save the energy in the throttling process, so the prototype of the quasi two-stage compression heat pump system coupled with ejector prototype was developed. Studying on this system coupled with ejector can enlarge the application of air-source heat pump in cold regions, which has a great meaning for satisfying the request of durative development. In this paper the system coupled with ejector is studied in detail by experimental method.The construction design of the ejector is the basis of studying on the quasi two-stage compression heat pump system coupled with ejector. Combing with the main studying content in this paper, the working principle and construction design principle of the ejector with conical mixing chamber is introduced firstly, the achievable ejection pressure (medium supplementary pressure) is calculated in theory, and the calculated process is achieved through computer program, which offer an academic basis for designing ejector.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 mathematic model of ejector is set up, and the working process of ejector is analyzed in thermodynamics. The system coupled with ejector is analyzed in thermodynamics in detail, and the calculated method of enthalpy of each state is presented.Thirdly, the experimental results of the quasi two-stage compression heat pump system coupled with ejector are analyzed in detail. The heating performance of this system coupled with ejector is compared with the conventional quasi two-stage compression system, and the refrigeration performance is compared with single-stage compression system. Comparing with the conventional quasi two-stage compression system, the heating capacity and heating COP of this system coupled with ejector is increased remarkably. The refrigeration capacity of this system coupled with ejector is obvious higher than that of the single-stage compression system, although the input power is higher, the refrigeration COP of this system coupled with ejector is still higher than that of the single-stage compression system.Finally, the ejection coefficient and ejector construction are optimized. Through testing on the ejectors by optimized design, it is concluded that: the appropriate ejection coefficient can improve the heating performance of the system coupled with ejector, and the ejector can adapt a wider range of operating conditions. For this system the optimized ejection coefficient is 0.1. The ejector with appropriate designing condition can adapt a wider range of operating conditions, and the system coupled with this ejector has higher heating capacity and heating COP, lower input power and discharge temperature. The heat pump coupled with the ejector by optimized design owns better performance in a wide range of operation conditions.