Three-Dimensional Numerical Simulation And Experiment Of Thermodynamic Cycle On Free-piston Stirling Heat Pump

In order to increase energy efficiency and protect the environment,in the face of the impact of refrigerant in steam compression air conditioning on the atmospheric environment,Stirling not only had the same theoretical thermal efficiency as steam compression cycles,but also had the advantages of being a clean,efficient,and small size.Therefore,Stirling had become the focus of research in recent years.To improve the efficiency of a Stirling heat pump and reduce the losses during operation,this thesis research on three-dimensional numerical simulation and experimental of a free-piston Stirling heat pump.With the purpose of in-depth analysis of the characteristics and losses of the free piston Stirling cycle,it explored the changes in its internal flow field,providing a reference for thermodynamic analysis.Firstly,this thesis analyzed the working principle of a free-piston Stirling heat pump and reasonably simplifies the heat exchanger.Established a physical model for a free piston Stirling heat pump,analyzed the heat transfer characteristics of the internal flow field,proposed simplification and assumptions,established a corresponding mathematical model for the physical model.Secondly,to research the distribution of the internal flow field of a free-piston Stirling heat pump,the working chamber of a free-piston Stirling heat pump was modeled,and the structured grid was generated.The method of combining FLUENT and UDF was used to obtain the transient flow field distribution of a free piston Stirling heat pump for one cycle.Through pressure drop analysis it was found that the key points of loss of the Stirling heat pump was the regenerator and heat exchanger.Analyzed the relationship between cycle indicator work and pressure and frequency.Pressure was positively correlated with cycle indicator work,while frequency was negatively correlated with cycle indicator work.Subsequently,to explore the heat transfer performance of grid-type heat exchangers,an approximate analytical model for circular tubes was established,and the correctness of the analytical solution for circular tubes was verified using numerical methods.The temperature distribution and heat transfer capacity of hexagonal tubes and circular tubes were analyzed for errors.Based on this small error within a reasonable range,an approximate circular tube model can be used instead of the hexagonal tube model.Finally,Building a free piston Stirling heat pump plate spring stiffness experimental platform and measured the stiffness of the plate spring.Established an experimental system consisting of a signal transmitter,a free piston Stirling heat pump,and a data acquisition system was built.The pressure in the expansion and compression chambers of a free piston Stirling heat pump was measured and the cycle indicator work was calculated.The reason for the error was analyzed by comparing the experimental results with the simulation results.In summary,the working mechanism of a free piston Stirling heat pump was introduced by this thesis analyzes and the flow field distribution in the working chamber;Through pressure drop analysis it is concluded that the largest part of the energy loss of the Stirling heat pump is the regenerator;Thermodynamic error analysis was conducted to verify that the regenerators with different structures can be replaced equivalently;Finally,the experimental results of the Stirling heat pump were compared with the simulation results,verifying the correctness of the numerical simulation,which had important guiding significance for the theoretical research of the Stirling heat pump.