Experimental Study Of Ejector Heat Pump And Control Mechanism Of Its Key Component

In view of the contradiction of low heat exchange efficiency in the field of building district heating,serious waste of waste heat in the industrial field and huge heat demand.The key theory and technical method of using ejector heat pump technology to improve the low temperature energy quality and make it recycled are put forward.Working fluid optimization of the system,the design of fluid and solid coupling of the ejector and optimization matching are explored.The interaction relationship between internal and external factors of energy saving mechanism is explained.The experimental research of ejector heat exchange system is carried out.In order to broaden the application range of ejector,a design method of a built-in regulation mechanism of the double-slider ejector is proposed,which can effectively solve the problems that the traditional ejector is difficult to adapt to the wide variation of heat load,poor adjustment performance and low entrainment ratio of ejectors under off-design working conditions.Firstly,combined with the energy analysis and the exergy analysis methods,the one-dimensional thermodynamic model of ejector and the thermodynamic model of ejector heat pump system were constructed,and the comprehensive technical and economic evaluation index of the system was put forward,which provided a theoretical basis for the selection of working fluid.In order to reveal the interaction relationship and the improvement potential of each component,the construction principle of advanced analysis method of the ejector heat pump system was proposed.The results showed that the comprehensive performance of the system with R141b was the optimum.Among all the components of the system,the exergy loss of the ejector was the largest,and the avoidable endogenous exergy loss accounted for55.18%.Moreover,the energy conversion mechanism of ejector heat pump system was expounded based on the concept of energy grade in the process of thermal cycle.Based on the optimization results of working fluid,R141b ejector was designed and developed using the numerical analysis method,and a small test-bench of ejector heat exchange system was built,which achieved the goal of greatly reducing the return water temperature of the secondary network under the low-temperature drive of the ejector heat pump.The results showed that the lowest return water temperature of the secondary network could be reduced to 25.1℃.Compared with the traditional secondary supply and return water temperature of 75/50℃,the circulating water flow of the user side could be increased to 1.99 times at most and the exergy efficiency was increased by 27.95%,and the cost per unit exergy could be reduced by 17.78%when the secondary circulating water flow was unchanged.Finally,based on the combination of aerodynamics theory and numerical analysis,a double-slider adjustable ejector was designed,and the influence of main operating parameters on the performance of the ejector was numerically simulated,which could provide a theoretical basis for the optimization of the adjustable ejector.An adjustable ejector performance test-bed with a maximum flow reduction rate of52.13%was built.The results indicated the critical adjustment range of the primary flow pressure was 0.7-1.0 MPa.Within the range,the critical adjustment range of the reduction rate of the primary mass flow rate should be lower than 42.27%,and the optimal range should be within 31.27%.In this optimal range,the entrainment ratio was 0.23-0.29.Compared with the conventional single-slider ejector,the maximum increment in average entrainment ratio of the double-slider adjustable ejector was34.5%.Based on the experimental results,the technology scheme of an adjustable ejector coupled ethanolamine regeneration was proposed.The modified ethanolamine regeneration system with a heat load demand of 36217 k W has an annual standard coal saving of at least 2804.60 t,the water saving is 30481 t,the dynamic payback period is less than one year,the CO₂ emission reduction is 6991.86 t,and energy conservation and emission reduction is significant.